This striking satellite image shows two near-perfectly parallel tornado tracks in Mississippi that were carved into the ground after a deadly storm system triggered more than 100 twisters across the U.S. in early 2025.

Between March 14 and 16, a series of extreme thunderstorms broke out in the High Plains and Midwest thanks to an "expansive upper-level trough" of warm, moist air. This storm system triggered 113 tornadoes across 14 U.S. states, according to The Weather Channel. At least 42 people are believed to have been killed, according to NBC News.

One of the worst-hit states was Mississippi, which experienced 18 tornadoes. Half of these reached at least Level 2 ("considerable damage") on the Enhanced Fujita scale (EF Scale), which measures the damage caused by a tornado. Around 1,000 houses were damaged in the state, according to the Mississippi Emergency Management Agency. Dozens of businesses and farms were also hit.

In this satellite image, you can see two different tracks that were carved out by two separate tornadoes just outside of Tylertown, Mississippi. The longer and wider track stretches up to 55 miles (89 kilometers), while the smaller track is only around 9 miles (15 km) long. It is unclear which one appeared first, or how much time passed between the respective twisters.

Related: See all the best images of Earth from space

The larger of the two tornadoes is believed to have reached Level 4 ("devastating damage") on the EF Scale, making it the single most powerful twister of the entire storm system, according to NASA's Earth Observatory. Its wind speed likely reached 170 mph (274 km/h), which is equivalent to a Category 5 hurricane.

Around 50 miles (80 km) northeast of Tylertown, aerial photographs revealed another pair of tornadoes had passed at right angles to one another, creating a large X-shape in a forested area of Covington County, according to the National Weather Service station at Jackson, Mississippi.

2025 has been one of the worst years for U.S. tornadoes in recent memory, partly due to the recent La Niña phenomenon, which altered the trajectory of the Pacific jet stream above North America, creating drier and warmer conditions in southern states, according to the National Oceananic and Atmospheric Administration (NOAA).

March was particularly extreme, with a record 299 twisters recorded during that month, according to the National Centers for Environmental Information. (For context, the entire U.S. normally only experiences around 80 twisters during March, on average.)

But even without La Niña, the frequency of tornadoes has been increasing over time due to rising sea surface temperatures off the Gulf coast — a direct result of human-caused climate change.

Like other types of extreme weather, such as wildfires, heatwaves and floods, climate change is also making tornadoes more powerful, costly and deadly. In 2023, for example, at least 26 people were killed by a single, nearly mile-wide "wedge tornado" that ripped through parts of Mississippi.

Additionally, tornadoes are now starting to impact places where they have not historically been seen before. Some researchers have previously suggested that "Tornado Alley" — the central region of the U.S. where tornadoes are traditionally most likely to occur, in states such as Texas, Oklahoma, Kansas, Iowa and Nebraska — could now be considered to be everything east of the Rockies.

Researchers at NASA's Langley Research Center are currently working on a way to better predict when tornadoes will form by analyzing cloud patterns in satellite photos. They hope that this could eventually warn people about an impending twister up to 10 minutes before it happens, potentially saving many lives, according to the Earth Observatory.

Violent tornado outbreaks, like the storms that tore through parts of St. Louis and London, Kentucky, on May 16, have made 2025 seem like an especially active, deadly and destructive year for tornadoes.

The U.S. has had more reported tornadoes than normal — over 960 as of May 22, according to the National Weather Service's preliminary count.

That's well above the national average of around 660 tornadoes reported by that point over the past 15 years, and it's similar to 2024 — the second-most active year over that same period.

I'm an atmospheric scientist who studies natural hazards. What stands out about 2025 so far isn't just the number of tornadoes, but how Tornado Alley has encompassed just about everything east of the Rockies, and how tornado season is becoming all year.

Why has 2025 been so active?

The high tornado count in 2025 has a lot to do with the weather in March, which broke records with 299 reported tornadoes — far exceeding the average of 80 for that month over the past three decades.

March's numbers were driven by two large tornado outbreaks: about 115 tornadoes swept across more than a dozen states March 14-16, stretching from Arkansas to Pennsylvania; and 145 tornadoes hit March 31 to April 1, primarily in a swath from Arkansas to Iowa and eastward. The 2025 numbers are preliminary pending final analyses.

While meteorologists don't know for sure why March was so active, there were a couple of ingredients that favor tornadoes:

• First, in March the climate was in a weak La Niña pattern, which is associated with a wavier and stormier jet stream and, often, with more U.S. tornadoes.
• Second, the waters of the Gulf were much warmer than normal, which feeds moister air inland to fuel severe thunderstorms.

By April and May, however, those ingredients had faded. The weak La Niña ended and the Gulf waters were closer to normal.

April and May also produced tornado outbreaks, but the preliminary count over most of this period, since the March 31-April 1 outbreak, has actually been close to the average, though things could still change.

What has stood out in April and May is persistence: The jet stream has remained wavy, bringing with it the normal ebb and flow of stormy low-pressure weather systems mixed with sunny high-pressure systems. In May alone, tornadoes were reported in Colorado, Minnesota, Delaware, Florida and just about every state in between.

Years with fewer tornadoes often have calm periods of a couple of weeks or longer when a sunny high-pressure system is parked over the central U.S. However, the U.S. didn't really get one of those calm periods in spring 2025.

Tornado Alley shifts eastward

The locations of these storms have also been notable: The 2025 tornadoes through May have been widespread but clustered near the lower and central Mississippi Valley, stretching from Illinois to Mississippi.

That's well to the east of traditional Tornado Alley, typically seen as stretching from Texas through Nebraska, and farther east than normal. April through May is still peak season for the Mississippi Valley, though it is usually on the eastern edge of activity rather than at the epicenter. The normal seasonal cycle of tornadoes moves inland from near the Gulf Coast in winter to the upper Midwest and Great Plains by summer.

Over the past few decades, the U.S. has seen a broad shift in tornadoes in three ways: to the east, earlier in the year and clustered into larger outbreaks.

Winter tornadoes have become more frequent over the eastern U.S., from the southeast, dubbed Dixie Alley for its tornado activity in recent years, to the Midwest, particularly Kentucky, Illinois and Indiana.

Meanwhile, there has been a steady and stark decline in tornadoes in the "traditional" tornado season and region: spring and summer in general, especially across the Great Plains.

It may come as a surprise that the U.S. has actually seen a decrease in overall U.S. tornado activity over the past several decades, especially for intense tornadoes categorized as EF2 and above. There have been fewer days with a tornado. However, those tornado days have been producing more tornadoes. These trends may have stabilized over the past decade.

Deadlier tornadoes

This eastward shift is likely making tornadoes deadlier.

Tornadoes in the Southeastern U.S. are more likely to strike overnight, when people are asleep and cannot quickly protect themselves, which makes these events dramatically more dangerous. The tornado that hit London, Kentucky, struck after 11 p.m. Many of the victims were over age 65.

The shift toward more winter tornadoes has also left people more vulnerable. Since they may not expect tornadoes at that time of year, they are likely to be less prepared. Tornado detection and forecasting is rapidly improving and has saved thousands of lives over the past 50-plus years, but forecasts can save lives only if people are able to receive them.

This shift in tornadoes to the east and earlier in the year is very similar to how scientists expect severe thunderstorms to change as the world warms. However, researchers don't know whether the overall downward trend in tornadoes is driven by warming or will continue into the future. Field campaigns studying how tornadoes form may help us better answer this question.

Remember that it only takes one

For safety, it's time to stop focusing on spring as tornado season and the Great Plains as Tornado Alley.

Tornado Alley is really all of the U.S. east of the Rockies and west of the Appalachians for most of the year. The farther south you live, the longer your tornado season lasts.

Forecasters say it every year for hurricanes, and we badly need to start saying it for tornadoes too: It only takes one to make it a bad season for you or your community. Just ask the residents of London, Kentucky; St. Louis; Plevna and Grinnell, Kansas; and McNairy County, Tennessee.

Listen to your local meteorologists so you will know when your region is facing a tornado risk. And if you hear sirens or are under a tornado warning, immediately go to your safe space. A tornado may already be on the ground, and you may have only seconds to protect yourself.

This edited article is republished from The Conversation under a Creative Commons license. Read the original article.

Earlier this year, a caver was poring over satellite images of the Nullarbor Plain when he came across something unexpected: an enormous, mysterious scar etched into the barren landscape.

The find intrigued scientists, including my colleagues and I. Upon closer investigation, we realized the scar was created by a ferocious tornado that no-one knew had occurred. We outline the findings in new research published today.

Tornadoes are a known threat in the United States and elsewhere. But they also happen in Australia.

Without the power of technology, this remarkable example of nature's ferocity would have gone unnoticed. It's important to study the tornado's aftermath to help us predict and prepare for the next big twister.

Australia's tornado history

Tornadoes are violent, spinning columns of air that drop from thunderstorms to the ground, bringing wind speeds often exceeding 124 miles (200 kilometers) an hour. They can cause massive destruction — uprooting trees, tearing apart buildings and throwing debris over large distances.

Tornadoes have been reported on every continent except Antarctica. They most commonly occur in the Great Plains region of the United States, and in the north-east region of India—Bangladesh.

The earliest tornado observed by settlers in Australia occurred in 1795 in the suburbs of Sydney. But a tornado was not confirmed here by Western scientists until the late 1800s.

In recent decades, documented instances in Australia include a 2013 tornado that crossed north-east Victoria and traveled up to the New South Wales border. It brought winds between 155 to 186 miles (250 to 300 km) an hour and damaged Murray River townships.

And in 2016, a severe storm produced at least seven tornadoes in central and eastern parts of South Australia.

It's important for scientists to accurately predict tornadoes, so we can issue warnings to communities. That's why the Nullarbor tornado scar was useful to study.

A whirlwind mystery

The Nullarbor Plain is a remote, dry, treeless stretch of land in southern Australia. The man who discovered the scar had been using Google Earth satellite imagery to search the Nullabor for caves or other karst features.

Karst is a landscape underlain by limestone featuring distinctive landforms. The discovery of the scar came to the attention of my colleagues and I through the collaborative network of researchers and explorers who study the Nullarbor karst.

The scar stretches from Western Australia over the border to South Australia. It lies 12 miles (20 km) north of the Trans-Australian Railway and 56 miles (90 km) east-north-east of Forrest, a former railway settlement.

We compared satellite imagery of the site over several years to determine that the tornado occurred between November 16 and 18, 2022. Blue circular patterns appeared alongside the scar, indicating pools of water associated with heavy rain.

My colleagues and I then traveled to the site in May this year to examine and photograph the scar and the neighboring landscape.

Our results have been published today in the Journal of Southern Hemisphere Earth Systems Science.

Related: 'You certainly don't see this every day': Ultra-rare backward-spinning tornado formed over Oklahoma

What we found

The scar is 11 kilometers long and between 525 and 820 feet (160 and 250 meter) wide. It bears striking patterns called "cycloidal marks", formed by tornado suction vortexes. This suggests the tornado was no ordinary storm but in the strong F2 or F3 category, spinning with destructive winds of more than 124 miles per hour (200 kilometers an hour).

The tornado probably lasted between seven and 13 minutes. Features of the scar suggest the whirling wind within the tornado was moving in a clockwise direction. We also think the tornado moved from west to east — which is consistent with the direction of a strong cold front in the region at the time.

Local weather observations also recorded intensive cloud cover and rainfall during that period in November 2022.

Unlike tornadoes that hit populated areas, this one did not damage homes or towns. But it left its mark nonetheless, eroding soil and vegetation and reshaping the Earth's surface.

Remarkably, the scar was still clearly visible 18 months after the event, both in satellite images and on the ground. This is probably because vegetation grows slowly in this dry landscape, so hadn't yet covered the erosion.

Predict and prepare

This fascinating discovery on the Nullarbor Plain shows how powerful and unpredictable nature can be — sometimes without us knowing.

Only three tornadoes have previously been documented on the Nullarbor Plain. This is likely because the area is remote with few eye-witnesses, and because the events do not damage properties and infrastructure. Interestingly, those three tornadoes occurred in November, just like this one.

Our research provides valuable insights into the tornadoes in this remote and little-studied region. It helps us understand when, and in what conditions, these types of tornadoes occur.

It also emphasizes the importance of satellite imagery in identifying and analyzing weather phenomena in remote locations, and in helping us predict and prepare for the next big event.

And finally, the results are a stark reminder that extreme weather can strike anywhere, anytime.

This article has been amended to clarify that a reference to early tornado observations relates only to the period after British invasion.

This edited article is republished from The Conversation under a Creative Commons license. Read the original article.

An ultra-rare backward-spinning tornado was spawned Tuesday (April 30) from a powerful supercell thunderstorm that formed over the Oklahoma-Texas border.

This backward tornado burst to life in the wake of another odd twister, which was unusual in that it looped back over its own path, CNN reported. Tornadoes tend to travel from west to east, because the prevailing winds in the U.S. travel in that direction and thus push storm systems that way. However, tornadoes can sometimes turn back on themselves as they lose strength; in this case, the tornado completed a full loop over its original path before dying out. 

This looping tornado had formed north of Loveland, Oklahoma, around 10 p.m. local time. It traveled east before heading north, west and then east again, over the same area it had already hit.

"You certainly don't see this every day," Rick Smith, a meteorologist with the National Weather Service (NWS) in Norman, Oklahoma, told CNN.

Related: 'Wedge tornado' in Mississippi is the deadliest in more than 50 years

As the looping tornado died down, the backward-spinning twister appeared a few miles southeast of Loveland, just before 10:30 p.m. Smith told CNN that both tornadoes were likely active for a brief period. 

A weather service warning called the tornado "large and extremely dangerous" and noted that it was "nearly stationary or moving very slowly south." It warned people located in Loveland, Grandfield and Devol that "This is a PARTICULARLY DANGEROUS SITUATION. TAKE COVER NOW!"

According to the NWS, nearly all tornadoes in the Northern Hemisphere have winds that whip counterclockwise around a central point; this motion is known as "cyclonic." But in about 1% of cases, twisters spin in the opposite direction; these are called anticyclonic. (In the Southern Hemisphere, cyclonic tornadoes spin clockwise, while anticyclonic ones spin counterclockwise.)

It was unusual enough to see a backward-spinning tornado, but the cyclone's lack of movement was also odd, Smith told CNN. And radar suggested the storm was strong enough to chuck debris thousands of feet into the air, even though anticyclonic tornadoes are often relatively weak.

Thankfully, the tornadoes mostly traveled over farmland, according to recent updates issued by Tillman County Emergency Management on Facebook. There have been no injuries, deaths or extensive structural damage reported, according to CNN.

Oklahoma has seen more than two dozen tornadoes this week. On April 27 and 28, a "slow-moving, but potent" storm triggered at least 27 tornadoes in Oklahoma and Texas, with 24 confirmed in Oklahoma, the NWS reported. 

A massive tornado that was nearly a mile (1.2 kilometers) long has killed at least 26 people and injured dozens more after devastating parts of western Mississippi on Friday (March 24) night.

The storm is the deadliest in over 50 years in Mississippi, records from the National Weather Service (NWS) suggest. It hit several small towns with violent, 166 to 200 mph (267 to 322 km/h) gusts of wind, and has received a preliminary rating of EF4 on the Enhanced Fujita Scale — the second-highest category in the NWS rating system — according to a Twitter post from the NWS in Jackson, Mississippi.

"Friday night was like nothing I've ever experienced," Zachary Hall, a storm chaser who watched the tornado sweep through the small town of Rolling Fork, wrote on Twitter. "This tornado was just… different. It was scary. It was loud. It had a growl. It was a terrifying beast in the dark that literally destroyed a town."

The tornado appeared broader than its height as it thundered through the Mississippi Delta, prompting storm observers to call it a "wedge tornado" after its unusual shape. However, the informal description carries no scientific meaning, as many factors can shape the width of a tornado, according to the National Oceanic and Atmospheric Administration.

Related: Bizarre 'worm tornado' in New Jersey has scientists baffled

The storm that caused the tornado was one of a larger storm system that raged across California and triggered severe flooding in Arizona, eastern Oklahoma and northern Virginia, according to the Washington Post. It gathered in strength as it traveled, fueled by high surface temperatures over the Gulf of Mexico and high altitude winds from the jet stream, which generated the spin necessary to whip up a violent tornado.

The wide, upside-down triangle tornado developed into a supercell storm — an uncommon but highly destructive thunderstorm with a rotating updraft and a separate downward air spiral, according to the NWS. These opposite air currents, which enable supercell storms to sustain themselves for longer than other storms, powered the deadly twister for 1 hour and 10 minutes over a distance of 170 miles (274 km).

"The conditions were just perfect for the storm to last a very long time, and that is usually not common," Lance Perrilloux, a meteorologist with the NWS in Jackson, told the BBC. "It caused that tornado to wreak havoc for a long distance."

The White House declared a federal emergency on Sunday (March 26) morning and unlocked funding for temporary housing, repairs and relief, according to a presidential statement.

While this monster storm was devastating, it was not the biggest on record. The widest ever documented tornado was the 2.6 mile-wide (4.2 km) El Reno tornado that churned across central Oklahoma in May 2013, killing eight people and injuring 151.

Damage from the tornadoes that ripped through the Midwest overnight Friday (Dec. 10) is still being assessed, but the violent storms will go down in history as some of the deadliest and longest-lasting, according to meteorologists. 

More than 30 tornadoes were reported across six states overnight — Arkansas, Illinois, Kentucky, Missouri, Mississippi and Tennessee — the National Weather Service tweeted, with one of those tornadoes (or perhaps a cluster) chiseling out a path of destruction about 250 miles (400 kilometers) long, The Washington Post reported. If that destructive storm was in fact a single entity, it will become the longest path of a single tornado in U.S. history, as well as the first so-called quad-tornado, meaning it swept through four states — northeast Arkansas, southeast Missouri, northwest Tennessee and western Kentucky, the Post said.

In just Kentucky, the death toll could rise to more than 70, CNN reported. And tornadoes reportedly caused the collapse of several large buildings, including a Mayfield Consumer Products candle factory (where 110 people are thought to have been at work), an Amazon warehouse in western Illinois (where at least two died) and a nursing home in Arkansas, CNN said.

Tornadoes form when denser cold air collides with and pushes down warm, moist air, resulting in thunderstorms. As the warm air rises, it creates an updraft. If winds are jostling that rising air, pushing it from side to side, the result can be a spinning storm. These spinning winds are most likely in supercells, which are the strongest types of thunderstorms. But even spinning air isn't always enough to spawn a tornado. For that to happen, air near the ground must both sink and rise; with enough of these rising and sinking wind gusts, the air near the ground begins to spin, according to the National Center for Atmospheric Research. 

And a long-lived tornado like the one that struck Friday night is even less likely, because the conditions have to be just right, said meteorologist and writer Bob Henson. "To get a long-lived tornado, you've got to have a long-lived tornado-producing thunderstorm. This is normally a supercell, a storm type that can maintain itself for hours with the help of strong vertical wind shear (winds that veer and/or increase with height) and continuous access to warm, moist air near the surface," Henson told Live Science in an email. 

And if too many of those thunderstorms form at once, they compete with each other, making it even more difficult for one to spawn a long-lived tornado. If the conditions are right for just a few strong thunderstorms to form, the environment right around the supercell must be perfect as well. Those localized conditions must be conducive to the circulation (or spinning) in the storm to extend to the ground for a prolonged period of time. "Only if all these factors come into alignment do you get a truly long-lived tornado-producing storm like the one that struck the Mississippi Valley on Friday night, which helps explain why these are so rare," Henson told Live Science.

This weekend's severe storms, and the tornadoes they spawned, were partly fueled by the warmer-than-average weather in the Midwest — which could experience temperatures some 40 degrees Fahrenheit (22.2 degrees Celsius) above average this week — a sign that climate change is rearing its head, the Post reported. 

Though the National Weather Service has yet to release a severity rating on the Enhanced Fujita scale for the quad-state tornado, the damage suggests it was on the upper end. That tornado leveled Mayfield, Kentucky, where debris was launched more than 30,000 feet (9,100 meters) into the air and homes were sliced off their foundations, the Post reported. 

"Last night was one of the most shocking weather events in my 40 years as a meteorologist — a violent tornado (in December!) drawing comparisons to the deadliest and longest-tracking tornado in U.S. history," tweeted Jeff Masters, a former hurricane scientist with the National Oceanic and Atmospheric Administration, who in 1995 founded the weather service called Weather Underground. 

The spate of intense tornadoes also indicates residents of tornado-prone regions need to be vigilant beyond the so-called tornado season that tends to peak in the spring. "It's certainly fair to say that Friday's disaster should disabuse anyone of the notion that tornado 'season' is limited to spring," meteorologist Bob Henson wrote for Yale Climate Connections on Saturday (Dec. 11). "Residents of the world's most tornado-prone nation have to be vigilant year round, especially in a climate where winter warm spells are getting warmer."

Originally published on Live Science.

Editor's note: This article was updated with additional information from meteorologist Bob Henson.

Twenty-two people died and more went missing after a series of tornadoes hit central Tennessee early Tuesday morning (March 3), including one that ripped through the urban core of Nashville. Many more people were injured, according to the state's governor, Bill Lee.

He said a statewide search and rescue effort was underway and that shelters had been opened around the state. Lee added that he had also requested federal support to manage the impacts of the storm. He encouraged Tennesseans to stay out of downtown Nashville and the other hard-hit areas.

"I encourage you all to pray for the families across our state that are facing tragedy right now and that are dealing with heartache and hardship in ways that only they know," Lee said in a news conference.

Related: Live updates on COVID-19

The first tornado alerts went off about 45 minutes past midnight local time.

"Confirmed tornado northwest of downtown Nashville. TAKE COVER NOW IF YOU ARE IN DAVIDSON, WILSON OR SUMNER COUNTIES!" the Nashville office of the National Weather Service announced.

The downtown Nashville tornado "shredded" more than 40 buildings, according to The Weather Channel. A photojournalist captured part of that tornado's passage on video, with several bright flashes appearing as the twister hit electrical infrastructure. According to PowerOutage.us, more than 20,000 homes and businesses remain without power as of this writing, down from 50,000 earlier.

Tornadoes are notoriously difficult to predict. Meteorologists might see a supercell storm forming, as happened over Tennessee last night, and most tornadoes spin off of those storms. But we can't yet predict which of these storms will spawn tornadoes, how bad those tornadoes will be or where within the storm they will touch down.

"It's easy enough to put a thunderstorm together. It's very difficult to get that thunderstorm to produce a significant tornado," Greg Carbin, the warning coordination meteorologist with the Storm Prediction Center in Norman, Oklahoma, told Live Science in 2011.

Tornadoes are relatively rare events, but they seem to occur when a block of rising warm air meets a block of falling cool air and both blocks spin horizontally — then get knocked on their sides. These twisters are most common between March and June in the United States, and they tend to touch down in "Tornado Alley." This wide, flat stretch of the country sits between the Dakotas and the Gulf Coast, bordered on either side by the Rocky Mountains and the Appalachian range.

As of Tuesday morning, search and rescue operations in Tennessee were ongoing and the extent of the damage was not fully understood.

• A history of destruction: 8 great hurricanes
• Hurricanes from above: Images of nature's biggest storms
• Photos: Hurricane Michael toppled over trees and uprooted 19th century artifacts

Originally published on Live Science.

A strong tornado moved through the outskirts of Kansas City yesterday (May 28), killing one person and injuring at least a dozen others. This was one of a string of tornadoes that have devastated parts of the U.S. in the last month.

On the western edge of Kansas City, the damage was extensive: The tornado ripped the roof off homes, knocked over trees and power lines, and threw piles of debris on now-impassable roads, according to The Kansas City Star. An estimated 13,000 people were left without power in the area, according to the Star.

On Monday (May 27) night, several tornadoes with winds up to 140 mph (225 km/h) tore through parts of Ohio and Indiana, killing one person, injuring at least 130 others and damaging dozens of homes, according to the Associated Press. 

Though tornadoes are common in these areas, especially in this season — tornadoes tend to peak in the U.S. South Plains in May and June — the number and strength of these tornadoes in Ohio were unusually strong, Andy Hatzos, a weather forecaster for the National Weather Service in Wilmington, Ohio, told Time.

Indeed, though the frequency of tornado outbreaks isn't increasing, the number of tornadoes in each outbreak as well as the number of days with multiple tornadoes, is increasing, according to NBC News. The average number of tornadoes in the past two weeks is twice that of the long-term average of tornadoes in each outbreak, they reported.

But it's unclear what's driving that uptick. Climate change is making weather events more extreme on average, but the exact role it played in the destruction over the past couple of weeks is tricky to untangle. But climate change is causing sea-surface temperatures to rise on average, something that can lead to atmospheric instability, a key ingredient for tornado formation, according to NBC News. [4 Things You Need to Know About Tornado Season]

Tornado watches this month have extended all the way to the East Coast, including Pennsylvania and New York City. These are just a few of over 500 warnings issued this month, according to CNN.

• Photos: The Tornado Damage Scale In Images
• Tornado Chasers: See Spinning Storms Up-Close (Photos)
• Image Gallery: Moore, Okla., Tornado Damage - May 20,

Originally published on Live Science.

Oklahoma, northwest Texas and the Texas Panhandle are bracing for a day of extreme weather, including dangerous tornadoes, flooding and thunderstorms.

"Numerous intense and long-track tornadoes" are expected in the region today (May 20) and tonight, according to the National Weather Services' Storm Prediction Center (SPC).

There's a 95% chance of tornadoes, 95% chance of winds over 75 mph (120 km/h), and 95% chance of hail larger than 2 inches (5 centimeters), according to the SPC. [Tornado Facts: Causes, Formation & Safety]

The SPC officially issued a tornado watch across the region. About 5.5 million people live in the region likely to be affected by the weather system, CBS News reported.

"The only other watch like this was issued for Alabama on 27 April 2011," the SPC tweeted.

As CNN pointed out, today is the sixth anniversary of a tornado that struck the city of Moore, Oklahoma, killing 24 people.

"A tornado watch means that conditions are favorable for tornadoes to form during the next several hours," the SPC said, urging residents to pay attention to local media for updates. "If a tornado warning is issued for your area, move to a place of safety, ideally in a basement or interior room on the lowest floor of a sturdy building."

Tornadoes can continue to form and will remain a threat after dark. And serious weather remains a threat in the areas outside the immediate zone of highest risk.

"More isolated but still potentially dangerous severe weather, including tornadoes and destructive winds and hail, is possible in surrounding parts of Texas, Oklahoma, Kansas, and Arkansas," the SPC said.

• In Images: Extreme Weather Around the World
• Top 11 Deadliest Natural Disasters in History
• Earth from Above: 101 Stunning Images from Orbit

Originally published on Live Science.

An image captured by a European Space Agency (ESA) orbiter recently showed what appears to be a very hairy, blue spider extending its "legs" across the Martian landscape.

But in reality, the so-called spider is a sprawling pattern left behind on a ridge by a frenzy of dust devils, when hundreds or even thousands of whirling tornadoes formed in the area, ESA representatives said yesterday (March 14) in a statement. [Seeing Things on Mars: A History of Martian Illusions]

The ESA-Roscosmos ExoMars Trace Gas Orbiter captured the image on Feb. 8 in Mars' Terra Sabaea region, using the spacecraft's Color and Stereo Surface Imaging System (CaSSIS). Blue tracks represent parts of the ridge that were scraped and scoured by the tornadoes' winds. Though the actual color of the material exposed by the tornadoes is dark red, it shows up as blue in the color-composite image; this technique enhances the contrast of surface features, according to the statement.

It is unknown why so many dust devils (or dust tornadoes) converged along the ridge, though the region's mountains may impact the flow of air masses and contribute to tornado formation, ESA representatives said.

The ExoMars orbiter, which launched in 2016, also captured a photo of NASA's InSight lander on March 2, as it pounded its burrowing "mole" instrument into the ground to sample Mars' interior. In the image, InSight appears as a small, white speck inside a darker circle of rock scorched by the lander's rockets during touchdown. Nearby are InSight's heat shield and parachute, which were ejected during its descent.

Other photos the ESA released yesterday feature stunningly well-preserved impact craters; layered deposits near Mars' south polar ice cap; and 3D views of craters, dunes and outcrops.

"All of the images we're sharing today represent some of the best from the last few months," Nicolas Thomas, CaSSIS principal investigator from the University of Bern in Switzerland, said in the statement. 

The "hairy spider" isn't the first eye-fooling photo of a Martian feature. In 1976, NASA's Viking 1 spacecraft snapped an image of a mountain on Mars that bore an uncanny resemblance to a human face, and the Curiosity rover has captured images that seemingly showed a rat, a lizard and even a floating spoon — unsurprisingly, they all turned out to be oddly shaped rocks.

• Mars Insight Photos: A Timeline to Landing on the Red Planet
• Goliath Birdeater: Images of a Colossal Spider
• The Search for Life on Mars (Photo Timeline)

Originally published on Live Science.

Picture a tornado forming. Does the funnel cloud in your mind's eye reach down from the sky like a malicious, spindly finger?

If so, that mental picture may be all wrong. New research suggests that tornadoes form not from the clouds down, but from the ground up.

In a new study presented yesterday (Dec. 13) at the annual meeting of the American Geophysical Union in Washington, D.C., Ohio University meteorologist Jana Houser argued that of four tornadoes observed in enough detail with a rapid radar technique, not a single one started its rotation in the sky. Instead, Houser and her team found, the tornado rotation began rapidly near the ground. [25 Strangest Sights on Google Earth]

"Tornadoes do not appear to form from the traditional, top-down mechanism," Houser told reporters at a news briefing.

Tracking twisters

Meteorologists know that tornadoes form when the winds in a strong storm begin to rotate. Predicting exactly when this will happen, and which storms will spawn strong tornadoes, is more difficult. A study from more than two decades ago using radar of tornado formation found that 67 percent of tornadoes formed from rotation in the clouds that extended toward the ground, Houser said. But that radar was relatively slow: It scanned each area of the horizon only every 5 minutes. Houser and her team used a rapid-scanning mobile radar unit that takes readings every 30 seconds and found that tornadoes formed far more rapidly than that, on the order of 30 seconds to 90 seconds.

With a more precise timescale, the researchers could also detect more accurately where rotation began — at least in a few tornadoes. Gathering good data on tornadoes is quite difficult, Houser said, because meteorologists can't know in advance where the twisters are going to hit. The research team has spent many hours monitoring storms that never spawned a tornado.

It's also very difficult to get radar measurements close to the ground, Houser said. Houses, trees and telephone poles interrupt the radar cone, leading to messy, hard-to-interpret data.

That's why the new research focused on only four tornadoes: A major one on May 24, 2011, outside of El Reno, Oklahoma, that registered a 5 out of 5 on the Enhanced Fujita (EF) scale, which ranks tornadoes by damage done; two minor EF1 tornadoes on May 25, 2012, outside of Galatia and Russell, Kansas; and finally, an EF3 tornado that hit outside of El Reno on May 31, 2013, with wind speeds of around 300 mph (483 km/h).

The El Reno tornado was the widest ever recorded, at 2.6 miles (4.2 km) across. It killed eight people, including three storm chasers who inadvertently ended up within the vortex while in their vehicle. For Houser and her team, the storm was extraordinary because the team happened to have deployed their mobile radar on a slight rise, giving them a clear shot to record data as low as 50 feet (15 meters) above ground level.

Ground truth

All four tornadoes formed from supercell storms. Otherwise, they were very different in strength and impact, Houser said. None, however, formed from the top down. In the case of the El Reno tornado, a storm chaser actually snapped a picture of the funnel cloud on the ground minutes before the mobile radar detected the tornado about 50 to 100 feet (15 to 30 m) above the ground.

"The tornado was very much confined to the lowest layer of atmosphere," Houser said.

Meteorologists have bandied about competing theories about tornado formation, Houser said, but this is the first time they've had good enough data to really test any of them.

The sample size of four was small, Houser acknowledged, but if tornadoes really do form from the ground up, forecasters are always going to be catching them several moments after they form by looking at radar data at cloud level. In order to improve tornado warnings, Houser said, it may be better to change the way meteorologists make tornado forecasts.

One possible avenue might be to use complex weather simulations to model a given storm as it develops, based on forecasting data a few hours before the storm hits, Houser said. Meteorologists could run a virtual version of a particular storm to see if it spawns tornadoes. Then, as the real storm develops, they could compare the tornado-forming models to the real-world data, searching for hints that a tornado might appear.

"Then you can be more confident in issuing a tornado warning based upon that model," Houser said.

• In Images: Extreme Weather Around the World
• Top 11 Deadliest Natural Disasters in History
• Earth from Above: 101 Stunning Images from Orbit

Originally published on Live Science.

Carr Fire in Northern California

The Carr Fire began near Highway 299 and Redding, California. The fire has burned over 110,000 acres (45,000 hectares) and killed six people, including two firefighters. It's also resulted in a terrifyingly enormous fire tornado. [Read more about the fire tornado]

Schoolhouse destroyed

A historic schoolhouse burned down when the Carr Fire tore through Shasta, California.

Park on fire

The fire was unstoppable and roared through Shasta State Historic Park.

Scorched remains

A Cal Fire firefighter sprays water on a home that was destroyed by the Carr Fire on July 27 in Redding, California. Over 1,000 structures have been damaged or destroyed.

Dousing flames

An elk head is seen mounted to a wall as a firefighter douses a burning home.

Widespread damage

Hundreds of structures have been completely destroyed by the Carr Fire.

Wildlife lost

A dead deer lies in front of a home that was destroyed by the Carr Fire on July 27.

Powerful flames

A drainage vent off Highway 299 that was filled with unknown debris caught fire and burned with an intense heat, producing billows of black smoke.

Complete destruction

Thousands of people have lost their homes in the Carr Fire.

Neighborhoods gone

A real estate sign is seen in front of a burning home during the Carr Fire in Redding, California, on July 27.

Fighting flames

Firefighters monitor a backfire during the Carr Fire in Redding, California, on July 27.

Burning sun

An eagle ornament at the top of a damaged flag pole is seen against the setting sun in an area scorched by the Carr Fire.

Numerous houses lost

A home burns along Sunflower Road during the Carr Fire on July 27.

Scrub jay survey

A California scrub jay perches on a burnt branch at Whiskeytown Lake in an area devastated by the Carr Fire.

Cat rescue

Fluffy, the white cat, was reunited with her owners who lost their home in the Lake Redding Estates section of Redding when the Carr Fire swept through their neighborhood.

In an apocalyptic scene, witnesses of the deadly Carr Fire near Redding, California, watched an enormous raging vortex of fire and smoke plow through their town on Thursday (July 26). The terrifying cyclone of flames was caught on camera and shared by ABC News.  

It's not unusual for fire whirls — also called fire devils, fire tornadoes or firenadoes — to erupt out of large wildfires such as this one. They're similar to a dust devil or a whirlwind, and occur when hot, dry air rises rapidly from the ground and forms a vertical column until it reaches cooler air high in the atmosphere. As more flames and hot air get pulled into the column, the structure starts to swirl into a vortex that pulls burning embers, flaming-hot gases and debris with it, creating a violent and dangerous tower of flames.

Typically, fire tornadoes are a few hundred feet high and last only minutes or seconds, but this one was different, KQED reported. On Thursday night, the fire near Redding exploded into a colossal fire tornado that reached 18,000 feet (550 meters) in the air and lasted nearly an hour, KQED reported. [See Photos of the Carr Fire Raging Across Northern California] 

"It's very rare as well to have these really persistent long-lived events like that," Neil Lareau, an atmospheric scientist at the University of Nevada, Reno, told KQED. "To get a big one like this is really scary."

Lareau told KQED that gigantic fire tornadoes have erupted during California wildfires before, but not in such densely populated areas, as was the case with this one. Last week, Redding reached 113 degrees Fahrenheit (45 degrees Celsius), which, Lareau said, helped create the perfect conditions for such an extreme fire event.

The Carr Fire has burned nearly 104,000 acres (42,000 hectares) since July 23, according to the California Department of Forestry and Fire Protection (Cal Fire). Thousands of people have lost their homes, and six people, including two firefighters, have lost their lives. The Cal Fire website lists "mechanical failure of vehicle" as the cause of the out-of-control inferno. 

Original article on Live Science.

Two weak tornadoes touched down in Fort Lauderdale, Florida, on Tuesday (April 10), damaging property, tearing up trees and scattering debris across the city's downtown as well as the Fort Lauderdale-Hollywood International Airport south of the city, the National Weather Service (NWS) reported.

No casualties associated with the tornadoes have been reported. One homeowner fled her residence when a fallen tree destroyed part of her roof, and a flood of rainwater poured into her home, according to the local news station WSVN Miami. The Red Cross is helping the woman relocate, the news station said.

Both tornadoes were classified as EF0, which is the weakest classification on the Enhanced Fujita intensity scale for tornadoes and pertains to sustained gales of 65 to 85 mph (105 to 137 km/h). [Photos: Tornado Damage Scales in Images]

According to the NWS, the first tornado blew through downtown Fort Lauderdale between 3:34 p.m. and 3:58 p.m. local time with peak winds of 65 mph. A second, stronger tornado formed near the airport  around 4:25 p.m., and blew for 10 minutes with winds reaching 84 mph. This second tornado toppled shipping containers and delayed flights.

A severe thunderstorm warning was in effect until about 5 p.m. local time, but the NWS didn't catch wind of the tornadoes until residents started sharing videos of the dark clouds swirling over the city via social media.

As Live Science previously reported, tornadoes generally form in the United States every spring and summer when warm, moist air blows north through the Gulf of Mexico and collides with the cold, dry air blowing south from Canada. When the two fronts meet, the cold air can form a kind of ceiling over the rising warm air, forcing the warm air to rotate in place instead of rising higher. More warm air rises throughout the day as the sun heats the ground until, finally, it breaks through the ceiling and pushes the cold air beneath it. The resulting column of wind can span up to 10 miles wide and whirl at more than 200 mph (322 km/h).

An average of 1,000 tornadoes are reported in the U.S. each year, according to the National Climatic Data Center, resulting in 80 deaths and 1,500 injuries.

Originally published on Live Science.

Watch the skies

Umbrellas and galoshes will shield you from rain, snow and hail — but what about showers of spiders, satellites, and raw mystery meat?

Humans, it turns out, have caught them all falling from the sky at one point or another. And while some freak rain occurrences are easily explained by atmospheric forces, others have endured for hundreds of years as unsolved meteorological mysteries. Join us now as we tick through some of the weirdest weather phenomena to ever face the planet, and see how many science can solve.

Frozen iguanas

While residents of Tallahassee, Florida braced for their first measurable snowfall in 28 years this January, other Floridians braced for a hailstorm of frozen iguanas. The cold-blooded lizards are an invasive species in Florida, where they like to make their homes in suburban tree branches. "When the temperature goes down, [iguanas] literally shut down, and they can no longer hold on to the trees," said Ron Magill, wildlife expert and communications director for Zoo Miami. The paralyzed iguanas tumble out of the trees and remain stock-still (but not dead) until temperatures warm, allowing them to revive and scurry off again. (Florida also saw an iguana rain in 2008.)

Fish

In Mexico, fish fall from the sky so often there’s a name for it: "lluvia de peces" (literally, rain of fish). In fact, coastal cities around the world from California to England to India have all seen their own versions of the fishy phenomenon — so what’s going on? Poseidon’s wrath aside, one possible explanation (though there are several theories) is that these fish-falls stem from weather events called waterspouts — basically, a tornado that touches down on water. Sometimes, when the whirling winds suck up water from lakes or oceans, they lift up schools of unsuspecting fish (and other water-life) with them. The winds carry the critters inland, then ultimately drop them on land with whatever water remains.

Frogs

Waterspouts may also be to blame for the straight-up-Biblical phenomenon of frog rain. Tiny toads have been recorded dropping from the sky at least since 1873, when an article in Scientific American reported, "a shower of frogs which darkened the air and covered the ground for a long distance" following a rainstorm in Kansas City, Missouri. The precise cause of the 1873 frog rain is unknown, but scientists generally apply this logic to frog falls: if a strong wind could overturn a car or rip a tree from the ground, it could certainly carry a frog far from its swampy home.

Meat

OK, but what makes chunks of meat drop from the sky? This question captivated America in 1876 when, over the course of several minutes, a field in Bath County, Kentucky was beset by a steady rain of what appeared to be flakes of beef . According to a report in Scientific American, two gentleman who tasted the puzzling sky beef could not agree on whether it was actually mutton or venison; a third man attested it was, in fact, bear. One analyst concluded it was not meat at all, but a type of cyanobacteria that congealed into a fleshy jelly when exposed to rain. Others were convinced it was buzzard barf. For better or worse, the mysterious Kentucky Meat Shower of 1876 remains that — a mystery.

Blood rain

Sometimes, microorganisms are easier to blame for weird weather phenomena. Case in point: Residents of several villages in northwest Spain received an unpleasant surprise in 2014, when they noticed that the water in their fountains had turned a gory shade of red. The tint wasn't left behind by a guilty murderer's bloody hands, but rather by microscopic algae that arrived in a recent rainfall. Studies confirmed that the "blood rain" was teeming with freshwater algae called Haematococcus pluvialis, which produce a red pigment when they're stressed.

Spiders

Millions of tiny spiders fell from the sky in Australia in 2015 — and it wasn’t the first time. This phenomenon, known as "spider rain" or "angel hair” (because of the silky, hairlike threads the spiders leave behind), occurs when huge groups of spiders engage in a behavior called "ballooning" at the same time. When ballooning, spiders "climb some high area and stick their butts up in the air and release silk — then they just take off," Rick Vetter, a retired arachnologist at the University of California, Riverside told Live Science at the time. "This is going on all around us all the time. We just don't notice it."

Golf balls

According to a local news report, "dozens and dozens and dozens" of golf balls littered the streets of Punta Gorda, Florida following a heavy downpour in 1969. The balls baffled the waterfront community; no golf courses or driving ranges in the area reported any balls missing. The likeliest explanation? Perhaps a waterspout passed over the pond at a nearby golf course, sucking decades of poorly-aimed balls into the Florida sky.

Russian gold

It rained gold in Siberia for a few glorious minutes in March 2018, when an old transport plane carrying an estimated $378 million in gold, platinum and diamonds accidentally spilled its cargo while taking off from Yakutsk Airport. According to airport officials, the plane's cargo hatch ripped open during takeoff, causing nearly 200 solid-gold bricks to tumble onto the runway and nearby snow. Sadly for treasure hunters, police say they have recovered all of the spilled booty.

Boiled bats

In January 2018, hundreds of heat-stricken bats fell from the trees of Campbelltown, Australia after a heat wave launched local temperatures up to 111.5 degrees Fahrenheit (44.2 degrees Celsius). The bats — a species of flying fox called Pteropus poliocephalus — can safely handle temperatures of about 86 degrees F (30 degrees C) before the heat addles their brains. After that, "they basically boil," Kate Ryan, the colony manager for the Campbelltown bats, told a local paper. More than 200 bats were ultimately found dead, many of them babies.

Various space stations

It’s exhausting work orbiting the Earth at 17,500 miles (28,000 kilometers) per hour. Satellites are generally pretty good about taking this speed in stride but, sometimes, they lose steam and fall. At press time, for example, China’s Tiangong-1 satellite — a 9.4-ton (8.5 metric tons) prototype space station — is tumbling inexorably toward Earth, expected to break apart in the planet’s atmosphere in the next few weeks. It will not be the first: over the past 50 years, more than 5,900 tons (5,400 metric tons) of space debris has survived re-entry into Earth's atmosphere. Luckily, your odds of being hit by such debris are about a million times smaller than your odds of winning the Powerball jackpot — so play on!

Deadly and expensive

It's too soon to say how much damage Hurricane Harvey inflicted on Houston in late August, but the total will likely be astounding.

Harvey will hardly be the first storm to cause destruction, however: Since 1965, at least 27 hurricanes have each resulted in damages of $1 billion or more, according to the National Oceanic and Atmospheric Administration (NOAA).

In a 2011 report, NOAA tallied "the deadliest, costliest and most intense" hurricanes to hit the United States from 1851 to 2010. These tallies are not adjusted for inflation but show just how expensive these storms can be.

Read on to see the 20 costliest and most damaging hurricanes to hit the United States in recorded history, according to NOAA.

No. 20: Agnes, 1972

Agnes, the first named storm of the 1972 hurricane season, reached hurricane strength on June 18, over the Gulf of Mexico. It made landfall on June 19 in Florida as a Category 1 hurricane with wind speeds measuring 74 mph (119 km/h), but its impact grew more dramatic after it traveled northward. On June 23, Agnes combined with a low-pressure system to bring drenching rainfall of up to 14 inches (35 centimeters) to states along the U.S.' northeastern coast, with up to 19 inches (48 cm) soaking parts of western Pennsylvania.

Though Agnes was considered a "weak" storm by hurricane standards, the damage caused by its floodwaters was considerable. By the time the storm dissipated, on June 25, severe flooding from the Carolinas to New York had caused 122 deaths and made Agnes the costliest hurricane to date.

Total damage: $2.1 billion

Original article on .

No. 19: Frederic, 1979

Frederic made landfall on Dauphin Island, Alabama, on Sept. 12, 1979, as a Category 3 hurricane, with peak wind speeds of 145 mph (233 km/h). The storm's high-speed gusts downed trees and destroyed structures across Alabama and Mississippi, leading to blocked roads and causing power outages that lasted for weeks in some areas. A storm surge of 12 to 15 feet (4 to 5 m) caused damage to buildings that extended for 80 miles (129 km) along the Alabama coast.

Approximately 500,000 people were evacuated from the central Gulf Coast region ahead of the hurricane. Though the storm caused five deaths, a report generated Sept. 13, 1979, by NOAA praised agencies and volunteers for the evacuation efforts responsible for keeping many people safe, saying that their actions "undoubtedly saved hundreds of lives."

Total damage: $2.3 billion

No. 18: Dennis, 2005

Dennis roared into Cuba on July 8, 2005, with winds gusting up to 145 mph (233 km/h). It weakened briefly, but then regained hurricane strength over the Gulf of Mexico. It touched down in western Florida on July 10 as a Category 3 hurricane, with peak wind speeds of 121 mph (195 km/h). After crossing into southwestern Alabama, Dennis weakened to a tropical storm and continued northward.

The relatively small and fast-moving storm produced less rainfall than other major hurricanes, averaging about 3 to 5 inches (8 to 12 cm) in most of the region it affected. Much of northwest Florida's cotton crop suffered damage due to high winds and rain, and two U.S. Air Force bases in Florida reported storm damage totaling more than half a billion dollars, the NWS reported. Three people died as a result of the storm, and their deaths were due to improper use of electrical generators, according to the NWS.

Total damage $2.55 billion

No. 17: Georges, 1998

Over Georges' 17-day life span, the storm made landfall seven times from the Caribbean to Mississippi and caused 602 deaths, mostly in Haiti and the Dominican Republic, according to a report produced by the National Hurricane Center.

Georges struck Key West, Florida, on Sept. 25, 1998, as a Category 2 hurricane, with maximum wind speeds of 104 mph (167 km/h). The storm maintained Category 2 strength as it moved through the Gulf of Mexico to make landfall again in Alabama on Sept. 28, with gusts reaching speeds of 110 mph (177 km/h). It brought storm surges that reached heights of 12 feet (4 m) in Alabama, and up to 10 feet (3 m) in Florida, and dumped rainfall measuring an average of 10 to 20 inches (25 to 51 cm) over southern Mississippi and Alabama, leading to widespread river flooding that inundated homes and led to evacuations.

Agricultural devastation in the affected regions was significant; entire crops of soybeans, cotton and pecans were almost completely wiped out, the NWS reported.

Total damage: $2.77 billion

No. 16: Fran, 1996

Hurricane Fran, the second major hurricane to strike North Carolina during the 1996 hurricane season, caused so much damage that its name was officially retired from the hurricane name list, according to the NWS. Though North Carolina bore the brunt of the storm's damage, Fran also affected states from South Carolina to Ohio, and extended eastward into Pennsylvania and Maryland.

Fran made landfall at Cape Fear, North Carolina, on Sept. 5, 1996, with sustained wind speeds of 115 mph (185 km/h) that later peaked at 137 mph (220 km/h), battering a region already reeling from Bertha, a Category 2 hurricane that struck two months earlier.

In North Carolina, storm surges measuring as high as 12 feet (4 m) eroded the coastline, washed away beaches and destroyed buildings along the waterfront. Winds downed trees and knocked out power lines, leaving millions of people without electricity. Flooding in Virginia closed roads, destroyed hundreds of homes, and left more than 400,000 people without power. The storm caused 26 deaths, most of which were the result of falling trees, the NWS reported.

Total damage: $4.16 billion

No. 15: Gustav, 2008

Gustav formed in the Caribbean as a tropical storm on Aug. 25, 2008, reaching hurricane strength as it hurtled toward Louisiana. An estimated 1.9 million people evacuated southern Louisiana between Aug. 29 and Aug. 31 in anticipation of Gustav, the NWS reported.

The storm made landfall in Louisiana on Sept. 1 as a Category 2 hurricane. Gustav's sustained wind speeds of 110 mph (177 km/h) toppled trees and power lines, damaging homes and other structures, and causing the deaths of three people. Storm surges flooded parts of Mississippi and Louisiana, reaching heights of 12 feet (4 m), and heavy rains soaked the region, with reports of 8 to 11 inches (20 to 28 cm) falling between Aug. 31 and Sept. 3.

Total damage: $4.62 billion

No. 14: Opal, 1995

Falling trees caused by Hurricane Opal killed nine people in the U.S., and the storm's heavy rains and flooding claimed the lives of 50 people in Mexico and Guatemala.

Opal became a hurricane on Oct. 2, 1995, making landfall in Florida on Oct. 4 as a Category 3 hurricane with gusts reaching 115 mph (185 km/h). Alarmed by Opal's rapid intensification on the morning of Oct. 4, thousands of Gulf Coast residents evacuated all at once, leading to gridlock on major highways. Storm surges reached heights of 10 to 15 feet (3 to 5 m), destroying and damaging more than 1,000 homes and nearly 1,000 boats, and devastating infrastructure in coastal Florida.

Strong winds also damaged and destroyed properties in southern Alabama, and caused an estimated $25 million in damage to trees in the Conecuh National Forest in Andalusia, Alabama.

Total damage: $5.14 billion

No. 13: Isabel, 2003

Isabel struck the U.S. on Sept. 18, 2003, making landfall in North Carolina as a Category 2 hurricane with sustained winds close to 100 mph (161 km/h), and bringing storm surges of up to 8 feet (2.4 m) high that flooded rivers, destroying and damaging homes and other buildings.

The storm caused 51 deaths, and a combination of strong winds and ground saturated by rainfall led to numerous toppled trees and power lines, leaving over 4 million people without electricity.

Total damage: $5.37 billion

No. 12: Floyd, 1999

Floyd, a large and intense hurricane, made landfall at Cape Fear, North Carolina, on Sept. 16, 1999. After touching down as a Category 2 hurricane with maximum winds of 105 mph (169 km/h) and a storm surge reaching 15 feet (5 m), Floyd traveled north over North Carolina and southeastern Virginia, briefly returned to the Atlantic, and reached Long Island, New York, on Sept. 17.

As much as 15 to 20 inches (38 to 51 cm) of rainfall drenched parts of North Carolina and Virginia, according to the NWS. The new rainfall swelled existing rain accumulations deposited by a tropical storm two weeks earlier, leading to catastrophic and widespread flooding.

Floyd also produced at least 10 tornadoes in North Carolina, and was responsible for 56 deaths in the U.S.

Total damage: $6.9 billion

No. 11: Hugo, 1989

Hugo passed over the eastern part of Puerto Rico as a Category 4 hurricane on Sept. 19, 1989. It made landfall north of Charleston, South Carolina, on Sept. 22 while still at Category 4 strength, with sustained winds of 104 mph (167 km/h), gusts up to 120 mph (193 km/h) and storm tides of 20 feet (6 m).

Hugo's speed and large size brought powerful winds 200 miles (322 km) inland, reaching areas that are usually spared the brunt of coastal hurricanes, with winds gusting up to 100 mph howling through Charlotte, North Carolina, according to the NWS.

Total damage: $7 billion

No. 10: Jeanne, 2004

The eye at the center of Hurricane Jeanne was 50 miles (80 km) wide when the storm made landfall on Florida's eastern coast on Sept. 26, 2004, as a Category 3 hurricane, with peak winds estimated at 120 mph (193 km/h).

Jeanne brought storm surges reaching heights of more than 3 feet (1 m) on Florida's western coast. The storm also soaked Florida with rainfall up to about 8 inches (20 cm) across the state, with as much as 13 inches (33 cm) reported in some areas.

Prior to striking Florida, Jeanne's torrential rains caused severe flooding and mudslides in Haiti, leading to an estimated 3,000 deaths and leaving approximately 200,000 homeless, the National Hurricane Center reported in 2005.

Total damage: $7.66 billion

No. 9: Allison, 2001

Allison formed as a tropical storm on June 5, 2001, in the Gulf of Mexico near Galveston, Texas, making landfall later that day. Though Allison never reached hurricane strength, the storm stalled over the region, bringing four days of heavy rainfall — for 10 hours at a stretch, in some locations — leading to devastating flooding across southern Texas, particularly in Houston.

On June 9, Allison returned to the Gulf of Mexico, and then made landfall again on June 10 in Louisiana, bringing heavy rains and flooding to Mississippi, Alabama, Georgia, Florida and North Carolina, before dissipating on June 18 off the coast of New England.

In some parts of Texas, Allison deposited over 38 inches (96 cm) of rain, inundating highways and affecting 22 million people in the Houston area, according to a report published in 2011 by the National Weather Service (NWS). The storm also spawned 23 tornadoes and caused 41 deaths and, at the time, was the costliest hurricane on record in the U.S., officials with NOAA reported.

Total damage: $9 billion

No. 8: Hurricane Frances, 2004

When Frances hit Stuart, Florida, just after midnight on Sept. 5, 2004, its winds were blowing at 105 mph (169) km/h), making it a Category 2 hurricane. It killed seven people in the United States.

However, Frances weakened as it churned across Florida's peninsula, and it dropped to tropical storm status just before entering the Gulf of Mexico on Sept. 6. The storm then headed back toward land, hitting Florida's Big Bend region that afternoon, before eventually weakening into an extratropical storm over West Virginia on Sept. 9.

Frances didn't leave the country without making its mark. It produced an almost 6-foot (1.8 m) storm surge above normal levels in Florida, dropped 18.07 inches (46 cm) of rain on Linville Falls, North Carolina, and produced more than 100 tornadoes through the southeastern and mid-Atlantic states.

Total damage: $9.51 billion

No. 7: Hurricane Rita, 2005

Rita, a Category 5 hurricane, ripped apart parts of Texas and Louisiana and damaged the Florida Keys. It was responsible for seven deaths in the United States.

As it traveled northward through the Gulf of Mexico, Rita rapidly jumped from a Category 2 to a Category 5 hurricane in about 24 hours. But it was a Category 3 hurricane when it made landfall on Sept. 24, 2005, just east of the Texas-Louisiana border, with winds of 115 mph (185 km/h).

It caused storm-surge flooding of 10 to 15 feet (3 to 4.5 m) above normal tide levels in Louisiana, caused a surge in Texas' Lake Livingston, and flooded parts of New Orleans that had just been flooded by Katrina the month before.

Rita brought 5 to 9 inches (13 to 23 centimeters) of rain to Louisiana and Texas, and spawned about 90 tornadoes across the southern United States.

Total damage: $12.04 billion

No. 6: Hurricane Charley, 2004

Charley was a small but fierce hurricane that hit southwestern Florida in August 2004. It killed 10 people in the United States.

Charley sped toward southwestern Florida, intensifying to Category 4 status with 150 mph (241 km/h) winds on Aug. 13. It passed dangerously close to Orlando, and finally exited the state near Daytona Beach. Charley weakened after moving into the Atlantic, and hit South Carolina as a Category 1 hurricane on Aug. 14 before dropping to tropical storm status as it hit North Carolina on Aug. 15.

Charley was small; its fastest wind speeds were located just 7 miles (11 km) from the storm's center, which lessened the storm surge to just 7 feet (2.1 m). But the hurricane's violent winds overwhelmed Punta Gorda and Port Charlotte in Florida. It also produced 16 tornadoes in Florida, North Carolina and Virginia.

Total damage: $15.11 billion

No. 5: Hurricane Ivan, 2004

Category 3 Hurricane Ivan blew through Florida and Alabama in September 2004, killing 25 people in the United States.

Ivan made landfall just west of Gulf Shores, Alabama, on Sept. 16, with its winds blowing at nearly 120 mph (193 km/h). It weakened as it moved inland but managed to produce more than 100 tornadoes and heavy rains across the southeastern United States.

The hurricane then went back to sea in the Atlantic, looped around and re-entered the country in southern Florida. Then, it crossed to the Gulf of Mexico and finally petered out after hitting southwestern Louisiana as a tropical depression on Sept. 24.

Total damage: $18.82 billion

No. 4: Hurricane Wilma, 2005

Wilma hit on Oct. 24, 2005, relatively late in the hurricane season.

The Category 3 hurricane crossed the Florida Peninsula in 5 hours, killing five people in the state as the storm blasted northeastward. Lake Okeechobee recorded 92 mph (148 km/h) winds with a gust at 112 mph (180 km/h). Wilma also created 10 tornadoes as it passed through Florida.

Wilma left the state and passed through the western Atlantic, weakened and eventually reached Halifax, Nova Scotia, on Oct. 25.

Total damage: $21 billion

No. 3: Hurricane Andrew, 1992

Hurricane Andrew was the United States' third-costliest hurricane. It is responsible for 23 deaths in the country.

Andrew shot across southern Florida on Aug. 24, 1992, as a Category 5 hurricane. Private barometers measured its pressure at 23.23 pounds per square inch when it made landfall in Homestead, Florida, making it, in that instant, the third most intense hurricane to hit the U.S. Wind speeds reached as high as 177 mph (284 km/h).

Andrew led to a 17-foot (5.1 m) storm surge near its landfall spot in Florida. After leaving Florida, Andrew headed to the Gulf of Mexico, where it turned northward and hit Louisiana as a Category 3 hurricane on Aug. 26, drowning the state's coastlines with 8-foot (2.4 m) storm tides. Andrew also created a tornado that struck southeastern Louisiana, killing two people and injuring 32 others.

Total damage: $26.5 billion

No. 2: Hurricane Ike, 2008

Hurricane Ike was the nation's second-costliest hurricane. Ike was directly responsible for the deaths of 21 people in Texas, Louisiana and Arkansas. It was directly and indirectly responsible for the deaths of at least 28 people in eight other states, according to a 2011 estimate from NOAA.

Ike made landfall on Galveston Island on Sept. 13, 2008, as a Category 2 hurricane, with wind speeds of 110 mph (177 km/h). It crashed through eastern Texas and Arkansas, weakened over the Mississippi Valley on Sept. 14, and blew wind gusts of hurricane force through the Ohio Valley and into Canada. Ike prompted the evacuation of nearly 15,000 tourists from the Florida Keys and caused 2.6 million people to lose power in Texas and Louisiana and Texas, and another 2.6 million to lose power in Ohio. The Bolivar Peninsula and Galveston Bay areas of Texas were inundated with storm surges of 15 to 20 feet (4.5 to 6 m). Ike also brought 19 inches (48 centimeters) of rain to southeastern Texas.

Total damage: $29.52 billion

No. 1: Hurricane Katrina, 2005

Hurricane Katrina was the most destructive hurricane on record to hit the United States. It directly killed approximately 1,200 people, making it the third-deadliest hurricane in U.S. history. (Earlier estimates put fatalities at 1,500 people, but some of these deaths were indirectly related to the storm, NOAA officials said. Direct causes of death included drowning, a flood-related injury and heat exposure, according to a 2008 report.)

Katrina became a hurricane just before making landfall by the Miami-Dade County line in Florida on Aug. 25, 2005. The hurricane then moved across southern Florida into the Gulf of Mexico, where it strengthened into a Category 5 hurricane on Aug. 28, reaching wind speeds of 175 mph (281 km/h).

As it moved toward Louisiana and Mississippi on Aug. 29, it weakened into a Category 3 storm, with wind speeds of 125 mph (201 km/h). Even so, Katrina produced 33 tornadoes, and its storm surge caused waters up to 28 feet (8.5 meters) above normal tide level along Mississippi and up to 20 feet (6 m) above normal levels in Louisiana. This storm surge notoriously breached New Orleans' levies on Aug. 29, flooding 75 percent of the city.

Total damage: $108 billion

Faster than a tornado, speedier than the giant storm swirling on Jupiter — it's the world's fastest-swirling vortex, which scientists have created in a primordial soup of gluey particles meant to re-create the Big Bang.

The swirling particle soup rotates at head-snapping speeds — many times faster than the closest contenders.

However, don't expect this fast-spinning fluid to turn heads anytime soon, as the vortices occur in a material called a quark-gluon plasma that is so small that the signature of this whirling can be detected only by the particles it produces.

"We can't look at the quark-gluon plasma; it's on the scale of an atomic nucleus," said Michael Lisa, a physicist at The Ohio State University who works on the Relativistic Heavy Ion Collider (RHIC) collaboration, which produced the new results. [The Big Bang to Civilization: 10 Amazing Origin Events]

Hot soup

Right after the Big Bang, a hot primordial stew of elementary particles called quarks and gluons permeated the baby universe. These elementary particles are the building blocks of better-known particles such as protons and neutrons. This quark-gluon plasma has several unique properties. First, at a blazing 7 trillion to 10 trillion degrees Fahrenheit (3.9 trillion to 5.6 trillion degrees Celsius), it's the hottest known fluid. It is also the densest fluid and "nearly perfect" in that it experiences almost no friction, meaning it flows very easily.

To understand exactly what happened in those moments after the Big Bang, scientists have re-created this primordial particle soup in an atom smasher at the RHIC, at Brookhaven National Laboratory in Upton, New York. The RHIC smashes the nuclei of gold atoms together at nearly the speed of light and then uses ultrasensitive detectors to measure the particles that fly off the collision.

Whirling fluid

In the new study, the team analyzed the quark-gluon plasma's vorticity — essentially a measure of its angular momentum or, in colloquial terms, how fast it spins.

Of course, they had a unique obstacle: The RHIC can produce just a teensy amount of the material, and it lives very fleetingly, or about 10 ^ minus 23 seconds. So there is no way to actually "observe" this fluid in the traditional sense.

Instead, scientists look for signatures of its whirling, based on the particles emitted from the soup, Lisa told Live Science. On average, particles inside a spinning fluid should have spins that roughly align with the angular momentum of the fluid. By measuring how much the particles coming off this whirling soup are deflected from their expected path, the team could calculate a rough estimate for the fluid's vorticity — which roughly measures the local spinning motion. In particular, particles known as lambda baryons tend to decay more slowly than other particles, such as protons and neutrons, meaning the RHIC detectors could more easily track their paths before they vanished.

It turns out, the vorticity in the quark-gluon plasma makes the whirling motion inside a tornado seem like a calm day in the park. The vorticity is the fastest ever recorded — much more rapid than that of Jupiter's Great Red Spot, a swirling storm of gas. It's also faster than the previous record holder, a supercooled type of helium nanodroplet, the researchers reported Aug. 2 in the journal Nature.

Understanding the structure of fluid flow in the plasma could reveal insight into the strong nuclear force, which binds atoms together, the researchers said. Several competing particle theories make predictions about vorticity that could eventually be compared against these experimental results. However, scientists still know too little about the plasma's swirling properties to make definitive conclusions.

"It's too early to say whether it teaches us something fundamental," Lisa said.

Originally published on Live Science.

ATLANTA — As climate change proceeds, there will be more extreme weather events, and these events pose a threat to people's health, experts say.

The annual number of natural disasters appears to be increasing around the world, said Dr. Mark Keim, an emergency-medicine physician and the founder of DisasterDoc LLC. These include, for example, not only weather- and water-related disasters, but also geological disasters, such as earthquakes, and biological disasters, such as pandemics.

Data from the past 50 years show that 41 percent of all global disasters are related to extreme weather or water events, Keim said here on Thursday (Feb. 16), at the Climate & Health Meeting, a gathering of experts from public health organizations, universities and advocacy groups that focused on the health impacts of climate change. [5 Ways Climate Change Will Affect Your Health]

Experts in climate change predict that extreme weather events will increase in either frequency or severity, and these events are a very serious public health burden, Keim told Live Science.

Extreme-weather events fall into three categories: high-precipitation disasters (such as hurricanes and tornadoes), low-precipitation disasters (heat, droughts and wildfires) and sea-level rise disasters, Keim said. High-precipitation and low-precipitation disasters are currently affecting the United States, he added.

High precipitation disasters

High-precipitation disasters, which include storms, floods and landslides, can kill people in a variety of ways, Keim said. People can die from falls, electrocutions (from downed power lines), drowning (for example, during a hurricane) or asphyxiation (in a landslide), Keim said. In the United States, more deaths occur during the clean-up phase of hurricanes than during the actual storms, he added.

Data show that among people with any type of severe injuries, 50 percent die immediately, and another 30 percent of severely injured people die within the first hour, Keim said. (These data apply to any type of severe injury, from car accidents to hurricanes, he said.)

That means that 80 percent of all deaths from severe injuries occur within 1 hour of the event, which is deemed "the golden hour," he said.

But during a disaster, with winds blowing or the earth shaking, it's nearly impossible to reach victims within that golden hour, Keim said. So if doctors and experts want to reduce the number of deaths, they need to take a different approach: prevention, Keim said.

Deaths from tornadoes, for example, have decreased tenfold over the past 30 years, thanks to improved communication about storms and education, he said. Improved forecasting and early warnings allow people to get out of the area, he added.  

Low-precipitation disasters

Low-precipitation disasters also threaten health, Keim said. These include heat waves, droughts and wildfires.

Kim Knowlton, an assistant clinical professor of environmental health sciences at Columbia University Mailman School of Public Health in New York City, who also spoke at the meeting, elaborated on the health risks posed by heat.

"There is a clear warming trend and that threatens health," Knowlton said. "Heat waves, which are extreme heat events that last several days, are the No. 1 cause of U.S. weather fatalities, on average, over the last 30 years," she said.

Extreme heat poses a problem because it disrupts the body's natural ability to regulate its temperature, Knowlton said. [Roasting? 7 Scientific Ways to Beat the Heat]

Normally, the body regulates its internal temperature via the heart and lungs, Knowlton said. When its hot out, the heart beats faster, we breathe faster and we sweat to cool off, she said. But in extreme heat, these functions can't rid the body of enough heat, and our internal temperature rises, she said.

This can lead to a range of heat-related illnesses, from mild ones, such as heat cramps and fatigue, to more serious ones, such as fainting and heat exhaustion, to severe ones, such as heat stroke, which is fatal in more than half of all cases, Knowlton said.

But extreme heat doesn't only kill people directly through heat-related illnesses. It can also increase the risk of death from heart disease, respiratory diseases, kidney diseases and other illnesses, because of its wider effects on the body, Knowlton said.

Many people are vulnerable to heat-related illnesses, Knowlton said. These include infants, children, the elderly, outdoor workers, athletes, people with medical conditions, pregnant women, the poor, the homeless and people who live in cities, she said.

In addition, certain drugs, such as blood pressure medications, antidepressants and allergy medications, make people more susceptible to heat, Knowlton said.

This means that people who are "already struggling to stay healthy will be more challenged as climate change and heat continues," she said. 

Originally published on Live Science.

Tornadoes are the most violent storms in nature. An average of 800 tornadoes are reported each year, resulting in 80 deaths and 1,500 injuries. Tornadoes are a worldwide phenomenon, touching down in every continent save Antarctica.

Dangerous funnels

Tornadoes form when different temperatures and humidity meet. In the United States, warm, wet winds travel north from the Gulf of Mexico in the spring and summer, where they meet cold, dry, south-moving Canadian fronts.

Generally, warm air rises, but when the two fronts meet, the cold air can trap the warm air beneath it. Because the warm air cannot move upward, it begins to rotate. As the sun heats the ground, more warm air continues to rise, until finally the mass is strong enough to push through the cold air barrier. The rising warm air pushes the cold air beneath it, creating a rotating column that can span up to 10 miles, while twisting at speeds exceeding 200 mph (322 km/h). [12 Twisted Tornado Facts]

The spinning air may remain unseen until it picks up enough dust and debris for its shape to be visible. Tornadoes can last for a minute or an hour, and they can tear a damage path up to 10 miles (16 kilometers) long.

Tornadoes forming over warm water are known as waterspouts, and are most common in southern states and along the Gulf Coast. Occasionally, waterspouts can move inward.

How safe are you?

The region lying between the Rocky and Appalachian Mountains — known informally as Tornado Alley — has the highest number of tornadoes in the United States each year; however, no place is safe. Tornadoes can occur anywhere in the United States, as well as in other countries. In fact, the United Kingdom reports the most tornadoes by land area.

In 1987, a tornado tore through Yellowstone National Park in Wyoming at elevations reaching up to 10,000 feet (3,048 meters), making it the highest altitude violent tornado in the United States. [Photo Gallery: Tornado Chasers]

Tornado wind and debris cause most of the structural damage suffered, but nearly half of the injuries from such disasters occur after the tornado has left, during rescue work and cleanup. According to the Federal Emergency Management Agency, a third of these injuries come from stepping on nails. As such, it is important to remember to exercise caution even after the danger appears to have passed.

Tornadoes can occur at any time during the year, but they form most frequently in the spring and summer, depending upon your location. They are most likely to appear between 3 p.m. and 9 p.m., but again, they can occur at any time in the day or night.

Measuring a tornado

Tornados were once ranked by wind speed on the Fujita scale. It was upgraded to the Enhanced Fujita scale in 2007 and ranges from EF0 to EF5. An EF0 tornado may damage trees but not buildings, with winds ranging up to 85 mph (137 km/h). An EF5 tornado is devastating; winds exceed 200 mph (322 km/h), and buildings can be annihilated.

If a tornado hits

During strong thunderstorms, keep an ear on local weather alerts. FEMA encourages families to have a disaster plan in place for all contingencies, not only for tornadoes; this not only can keep you safe, but can allow for some peace of mind when families are separated. [Infographic: Tornado Season: What to Expect]

If your television or radio announces a tornado watch, this means that conditions are favorable for a tornado to form. Continue to listen for further updates. If a tornado warning is announced, it means a tornado has been sighted or indicated by radar. Move to a safe place immediately.

If a tornado strikes and you are inside a sturdy building, go to the lowest floor, such as the basement or storm cellar. If the building has no rooms beneath the ground, get to the lowest level possible and find an interior room, putting as many walls as possible between you and the tornado. Don't bother opening windows to equalize pressure; this will accomplish nothing except to allow more debris inside.

If you are in a mobile home or trailer, leave immediately. Find the lowest floor of a sturdy shelter, or a ditch or depression. Lie down flat and cover your head. Do not seek refuge under an overpass or bridge.

Never try to outrun a tornado. Instead, find a safe place to ride it out. Watch for flying debris, which causes the most fatalities and injuries while the tornado is in process.

Remember that almost half of tornado-related injuries occur after the tornado has ended. Be careful when entering buildings that have been damaged. Wear sturdy shoes and appropriate clothes to avoid scrapes. Monitor your radio for emergency information. Do not touched downed power lines or anything in contact with such lines. Watch (and smell) for gas line breaks.

Additional resources

• NOAA's Tornado information
• FEMA's tornado page
• CDC's Emergency Preparedness and Response information
• Active Junky's Emergency Survival Checklist

Damaging, deadly tornado clusters are becoming more common, a new study finds.

Tornado clusters are outbreaks of twisters that span several days. One terrifying example is the April 25-28 outbreak in 2011, when some 350 tornadoes ripped across the south-central United States, killing more than 300 people.

Outbreaks are responsible for 79 percent of tornado-related fatalities, said Michael Tippett, a climate and weather researcher at the School of Applied Science and Engineering and the Data Science Institute, both at Columbia University in New York. [Tornado Chasers: See Spinning Storms Up-Close (Photos)]

Tippett's new research shows the number of tornadoes per outbreak is increasing. The analysis also discovered a 4-fold increase in the chance of extreme outbreaks — when hundreds of tornadoes spawn in storms.

The researchers analyzed National Oceanic and Atmospheric Administration (NOAA) tornado records from 1954 to 2014. Outbreaks were counted when six or more EF-1 tornadoes started within 6 hours of each other, no matter the location. The scientists calculated the average number of tornadoes per outbreak, as well as variability— swings between high and low numbers of twisters — which relates to the chance of extreme outbreaks..

The findings were published Feb. 29 in the journal Nature Communications. The study was coauthored by Joel Cohen, a mathematical population biologist and head of the Laboratory of Populations at Rockefeller University in New York and Columbia's Earth Institute. 

"These discoveries suggest that the risks from tornado outbreaks are rising far faster than previously recognized," Cohen told Live Science in an email interview.

The researchers analyzed National Oceanic and Atmospheric Administration (NOAA) tornado records from 1954 to 2014. Outbreaks were counted when six or more EF-1 tornadoes started within six hours of each other, no matter the location. They calculated the average tornadoes per outbreak, as well as variability — swings between high and low numbers of twisters.

The total number of tornadoes (rated EF-1 and above) per year remained steady since the 1950s, the study reported. The Enhanced Fujita scale, or EF scale, ranks tornadoes based on wind speeds and damage. A tornado with wind speeds between 86 and 110 mph (138 and 177 km/h) is usually rated an EF-1. The highest rating is an EF-5. [See the Tornado Damage Scale in Images]

However, the average number of tornadoes per outbreak rose from about 10 in the 1950s to about 15 in the past decade. The variability around that average rose four times faster. This statistical link, known as Taylor's power law, has been observed in other fields but never before with severe weather, Tippett told Live Science in an email interview.

The new findings are consistent with several recent studies that suggest U.S. tornadoes are becoming more likely to strike in clusters. A NOAA study, published in October 2014 in the journal Science, showed a rise in the number of days with multiple reported tornadoes. Another study, published in July 2014 in the journal Climate Dynamics, found a similar clustering of tornadoes.

The researchers said they can't blame climate change for the uptick in tornado outbreaks. However, the warming planet could be shifting weather patterns across the United States and triggering more tornadoes. For instance, extreme weather systems that spawn storms are now more likely to get stuck in one place for several days. Increasing warmth may also boost tornado outbreaks by sparking unstable weather earlier in the year.

"We want to know what in the climate system is driving these changes. Some have implicated climate change. We think such a conclusion is premature, and further study is needed," Tippett said.

Follow us @livescience, Facebook & Google+. Original article on Live Science.

Severe storms have been hammering the southeastern United States this week, with tornadoes and strong winds tearing through towns from Louisiana to Florida. In New Orleans, stormy weather on Tuesday (Feb. 23) created a unique phenomenon over Lake Pontchartrain: three simultaneous waterspouts whirling across the water.

There are two main categories of waterspouts: fair weather and tornadic, according to NOAA. Fair-weather waterspouts typically develop on the surface of the water and move upward. They tend not to move much, and aren't generally associated with thunderstorms, NOAA said.

Tornadic waterspouts, on the other hand, behave similarly to land tornadoes: They develop downward and can migrate. The waterspouts spotted earlier this week were likely of the tornadic variety —one main tornado developed first, followed by two satellite tornados, reported The Washington Post. However, that particular storm did not produce any other tornadoes, according to AL.com, and the three waterspouts seen over Lake Pontchartrain did not make landfall. [Weirdo Weather: 7 Rare Weather Events]

The formation of any tornado is associated with supercell thunderstorms, which are storms with deep rotating updrafts, or mesocyclones, according to National Geographic. However, not all supercells produce tornadoes. In fact, the events surrounding tornado formation remain mysterious, and scientists "still don't know why some thunderstorms create tornadoes while others don't," legendary storm chaser Tim Samaras told National Geographic in 2013. (Samaras and two other members of his storm-research team were killed in May 2013 by a violent tornado in El Reno, Oklahoma.)

Tornadoes are notoriously difficult to predict, because they can form so quickly and can move erratically. The average warning time for a tornado is 13 minutes, reported National Geographic.

Researchers do know that high relative humidity, wind changes in the lower atmosphere and a specifically placed downdraft are necessary ingredients to create a tornado. Temperature also plays a crucial role, according to National Geographic. Cold, dry air must lie above warm, moist air to generate a tornado. The warm air will rise rapidly, and the changing winds in a supercell will rotate the updraft. The process is finicky, though, and if the air is too cold it can choke the inflow of new air and kill the tornado, reported National Geographic.

Satellite tornadoes are a weather phenomenon in which smaller tornadoes rotate around a central, primary tornado, all interacting with the same mesocyclone. In other circumstances, a tornado can have several vortices inside of the main vortex, but these are much harder to see with the naked eye, according to NOAA. These weather events are all distinguishable from tornado outbreaks, in which multiple tornadoes originate from separate supercells.

Two or more simultaneous tornadoes can be seen if a new tornado spins up before an existing tornado dies, or if a particularly violent storm creates enough turbulence to produce several vortices. But a true satellite tornado is characterized by a peripheral location and because it orbits a primary tornado, according to NOAA's Storm Prediction Center in Norman, Oklahoma.

In June 2014, twin tornadoes struck the small town of Pilger, Nebraska. The Storm Prediction Center reported that such an event was likely to occur only every 10 to 15 years, making this week's Lake Pontchartrain event appear even more rare.

NOAA's Storm Prediction Center issued tornado watches for south Louisiana, Mississippi and parts of Alabama earlier this week. The system proceeded up the East Coast, wreaking havoc in Florida, North Carolina and Virginia. Tornado watches were issued in parts of the Northeast, including in the District of Columbia, Delaware, Maryland, southern New Jersey, southeast Pennsylvania and Northern Virginia.

Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

Everyone dies of something, but after slogging through the daily news, you'd think most people die from terrorism, shark attacks and gas explosions. But are these tragedies — not to mention deaths from lightning strikes, plane crashes and tsunamis — actually top killers in the United States?

Not really.

Even combined, these incidents killed far fewer people than the most deadly illness — heart disease, which took the lives of more than 614,000 people in the United States in 2014, accounting for about 23 percent of all deaths in the country, according to the Centers for Disease Control and Prevention (CDC).

To separate the deaths that make headlines from those that are far more common, Live Science investigated the odds of dying from various causes. We used the CDC's Wonder database for 2014 data and other sources, and found that you're more likely to die of Alzheimer's disease (about 29 deaths per 100,000 people in the U.S.) than you are from contact with a venomous snake or lizard (there were just five such deaths in 2014).

In total, about 2.6 million people died in the United States in 2014, according to the CDC. To put this number into perspective, that means about 824 people died for every 100,000 people in the country. (Keep this statistic in mind, as we'll be giving death rates per 100,000 people throughout this article.) Worldwide, an estimated 56 million people died in 2012, the most recent year for which numbers on worldwide deaths are available from the World Health Organization (WHO).

Although Hollywood advised us (in no fewer than five of its blockbusters) to "Die Hard," there are a ton of ways to die. Here's a look at how many people die from common, unexpected and even theoretical events, and the science behind those numbers. [9 Healthy Habits You Can Do in 1 Minute (Or Less)]

Ways to Die 

1. Top 2 Deadly Diseases
2. Top Killers
3. Respiratory Diseases & Accidents
4. More Diseases
5. Drug Overdoses
6. Animal Attacks
7. Transportation
8. Terrorism & Homicides
9. Other Scary Ways to Die
10. Natural Disasters

Top 2 Deadly Diseases

In decades past, infectious diseases were the No. 1 killer, "but with the advent of antibiotics and treatment of infectious diseases, people started to live longer," said Dr. Maan Fares, a staff cardiologist at Cleveland Clinic. With many infections now conquered, people's lifestyle choices — including whether they smoke, how they eat and how much they exercise — are catching up with them, and causing conditions such as diabetes, high blood pressure and high cholesterol, Fares told Live Science.

So, it may come as no surprise that the top two killers — heart disease and cancer — account for roughly half of all deaths in the United States. About 193 per 100,000 people died from cardiovascular problems, such as heart attacks, in the United States in 2014. Worldwide, cardiovascular diseases killed 17.5 million people, accounting for 3 of every 10 deaths in 2012, the WHO reported.

People's risk of heart disease rises with smoking, sedentary lifestyles and poor sleep. To lower your risk of dying of heart disease, you can exercise, eat colorful fruits and vegetables (and fiber), and drink less alcohol.

Cancer placed second, with about 186 deaths per 100,000 people in the United States. Some cancers took more lives than others. The top killers, lung and bronchial cancers, killed about 155,000 people in 2014, or about 49 deaths per 100,000 people. Colon and rectal cancers claimed about 16 lives per 100,000 people, and breast cancer took about 13 lives per 100,000 people. Pancreatic cancer and prostate cancer followed, with about 12.7 and 9 deaths per 100,000 people, respectively. [7 Cancers You Can Ward Off with Exercise]

"We still don't know what causes cancer, but we do realize that each cancer is different, and the risk factors associated with each is very different," said Dr. Rupal O'Quinn, a cardio-oncologist at the University of Pennsylvania. People with cancer are living longer and sometimes even beating their diagnosis, largely thanks to cancer screenings, organ transplants and targeted therapies (newer drugs that aim to specifically kill cancer cells, rather than the broader approach of chemotherapy drugs), O'Quinn said.  

There were 3 million cancer survivors in the country in 1971, and more than 12 million in 2012, according to a study in the International Journal of Medical Sciences. But there is still much to be learned about cancer, she said. Screening cannot look for every type of cancer, such as ovarian cancer, which may explain why some cancers claim more lives than others, O'Quinn said.

A person's cancer risk may also vary according to region. For instance, esophageal cancer kills about 4 per 100,000 people a year in the United States, but about 140 per 100,000 people in Central Asian countries such as Pakistan, according to a 2004 study in the journal Annals of Oncology.

The reason? Researchers suspect that the higher rates of esophageal cancer in Central Asia are linked to the use of chewing tobacco — a habit common in Pakistan — as well as the "drinking of very hot beverages such as tea and Kawa [or kahwa], which are again, extremely common in Pakistan," the researchers wrote in the study. (Drinking scalding-hot beverages is linked to an increased risk of esophageal cancer, a 2009 study in northern Iran found.)

People's risk of cancer generally rises the longer they live, but also with smoking, using tanning beds and sitting too much. To lower your risk of dying of cancer, you can get recommended screenings, exercise and eat a healthy diet.

Top Killers

The first eight diseases listed in the table below were the top eight killers in the United States in 2014, whereas the rest are shown for comparison purposes.

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Respiratory Diseases & Accidents

In the U.S., after cancer, the next two largest killers are respiratory diseases and accidents. Respiratory diseases such as bronchitis, emphysema and asthma killed about 46 per 100,000 people in 2014, the CDC found. People may lower their respiratory risk by kicking their cigarettes to the curb. Moreover, some evidence suggests that asthma may be prevented in young children if they live with a dog or are exposed to allergens early in life.

Avoiding accidents is a whole other ball game. Accidents include a whole range of unintentional injuries and accounted for about 43 deaths per 100,000 people, or about 5 percent of all deaths in the United States in 2014, the CDC reported. A word to the wise: Remember to take off your headphones if you're walking around town (it can distract you from cars), and don't speed while driving.

The fifth top killer in 2014 was cerebrovascular disease (strokes), which claimed about 42 lives per 100,000 people in the United States.

More Diseases

Other health conditions also took a toll. Influenza and pneumonia (the two conditions are lumped together in CDC statistics) killed about 17 per 100,000 people in the United States, or about 55,000 people in total. Of those, about 23,700 were people age 85 or older, and 186 were infants younger than 1 year old. But many cases of flu can be prevented through vaccination. The 2014 flu shot decreased people's chances of getting the flu by only 19 percent, but the vaccines developed between 2012 and 2013 decreased their chances by 56 percent, Live Science found.

Suicide took the lives of about 42,700 individuals in 2014, meaning that there were about 13 suicides per 100,000 people in the United States that year. It was the 10th leading cause of death in the United States, topping death by assault, which took about 13,000 lives that same year. The number for the suicide hotline is (800) 273-8255.

On other fronts, modern medicine is helping people manage their maladies. Human immunodeficiency virus (HIV) disease killed about 6,700 people in the United States in 2014, or about 2 per 100,000 people. That's substantially fewer deaths than the virus caused in 1999 (the first year listed in CDC Wonder), when HIV took the lives of about 14,800 people, or about 5 per 100,000 people. [Extending Life: 7 Ways to Live Past 100]

Worldwide, about 1.2 million people, including 150,000 children younger than age 15, died of HIV-related causes in 2014, WHO reported. That's about a 57 percent decrease from 1999, when about 2.8 million people worldwide died of the disease, according to the Joint United Nations Programme on HIV/AIDS. The drop is largely due to increased access to a drug regimen called antiretroviral therapy (ART), which keeps the virus at low levels within the body, and fewer people contracting the disease, the WHO said.

Other diseases that plague the world are very uncommon in the United States. For instance, malaria killed eight people in the U.S. in 2014 but caused 584,000 deaths worldwide, 90 percent of them in Africa, according to the WHO. Moreover, tuberculosis killed 493 people in the United States, or 0.2 per 100,000 people in 2014. Worldwide, the respiratory disease killed 1.5 million people, the WHO found.

Drug Overdoses

A total of 47,055 people died of drug overdoses in the United States in 2014, or 14.7 deaths per 100,000 people. The number is alarming, as it represents an increase of 6.5 percent over the previous year, the CDC said.

"More persons died from drug overdoses in the United States in 2014 than during any previous year on record," the CDC wrote in a Jan. 1 report. "In 2014, there were approximately one and a half times more drug overdose deaths in the United States than deaths from motor vehicle crashes." Deaths from opioids (including opioid pain relievers and heroin) came in at 9 deaths per 100,000 people in 2014 — a 14 percent increase from 2013. In fact, 61 percent of drug overdose deaths included some type of opioid, the CDC said.

Animal Attacks

Many people automatically think of sharks when they imagine deadly animals, but they're far from a leading cause of death. CDC Wonder doesn't always mention the exact animal, but it noted that nobody in the U.S. died from "contact with a marine animal" such as a whale or a shark in 2014 (although three people died in this category in 2013).

However, in 2014, six people died after being bitten or stung by a nonvenomous insect, 36 people died after being bitten or mauled by a dog and 83 died after being struck by a mammal (not including dogs), such as a cow or a horse. But rest assured — no one in the U.S. reportedly died from rat bites or crocodile or alligator attacks in 2014. Furthermore, there were no deaths from "contact with plant thorns and spines and sharp leaves," though it's good to know that's a category the CDC can use just in case. [In Photos: The 10 Deadliest Animals]

Worldwide, the deadliest animal (after the mosquito, which kills people with the illness-causing pathogens it carries) is perhaps the snake. Snakebites kill 20,000 people globally each year, according to a 2008 study published in the journal PLOS Medicine.

Transportation

In the United States, people are much more likely to die while walking on a roadway than from tuberculosis or getting mauled by an animal, the odds show. In the United States, there were about 37,000 deaths from "transport accidents" (including car, train, motorcycle and boat accidents). This number includes 6,200 pedestrians who died in transportation collisions — such as crashes with cars, trucks, bikes and trains — meaning that 2 pedestrians died per 100,000 people.

In fact, more pedestrians died in the United States than motorcyclists (about 4,100 deaths) and bicyclists (about 900 deaths) combined, according to CDC Wonder. But death rates from vehicle accidents are still the highest: More than 7,800 people died in a car, pickup truck, van, heavy transport vehicle (such as a semitruck) or bus accident in 2014. That's 2.5 per 100,000 people, according to CDC Wonder.

Of the deaths due to traffic accidents in the U.S., 31 percent were due to alcohol, according to the National Highway Traffic Safety Administration (NHTSA). Of the motor-vehicle-related deaths, speeding accounted for 28 percent, distracted driving for 10 percent and drowsy drivers for almost 3 percent, the NHTSA said.

Terrorism & Homicides

In 2014, there were more than 32,700 deaths related to terrorism worldwide, according to the U.S. Department of State. (The department has yet to post data from 2015, and undoubtedly, these numbers have increased due to the conflicts in Syria and elsewhere.)

More than 6,200 of the 32,700 people (19 percent) killed were perpetrators. These people died after committing suicide, by accident or from security forces or victims responding to the attacks, the department reported. The terrorist attacks happened in 95 countries, but 78 percent of all terrorism fatalities took place in Iraq, Nigeria, Afghanistan, Pakistan and Syria, the department said.

Large attacks increased from 2013 to 2014. In 2013, there were two attacks that killed more than 100 people, but in 2014, there were 20 attacks of this size. Moreover, the death count increased by 81 percent in 2014 compared to in 2013, largely because of terrorist activities in Iraq, Afghanistan and Nigeria, the department reported.

Of course, it's hard to define terrorism, but the department makes an attempt. Terrorism is a violent act "aimed at attaining a political, economic, religious or social goal" that seeks to "coerce, intimidate or convey some other message to a larger audience," according to the report. Terrorism also breaks international humanitarian law by targeting "noncombatants," or innocent people.  

In the United States, about another 10,900 people died from an assault by a handgun, rifle, shotgun, larger firearm or unspecified firearm discharge in 2014, accounting for 3.4 deaths per 100,00 people, the CDC reported. (In this case, "firearm assaults" do not include suicides, unintentional shootings, shootings of undetermined intent, justifiable shootings, war or terrorism.)

Other Scary Ways to Die

For comparison, the table below lists the deaths caused by some of the more sensationalized means, also in 2014. These figures tend to vary significantly from year to year, and in the case of some — like deaths from venomous spiders — can be just a handful, or zero. They tend to be so low that when the rate of deaths per 100,000 people is calculated, the result is insignificantly tiny.

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Natural Disasters

Preparedness can make a world of difference when natural disasters strike. Take tsunamis, for instance. Since 2000 B.C., there have been about 2,400 tsunamis that have killed at least 500,000 people, according to the National Oceanic and Atmospheric Administration (NOAA). But the 2004 Sumatra and 2011 Tohoku (Fukushima) tsunamis were the deadliest waves in recent history. [Fukushima Radiation Leak: 5 Things You Should Know]

About 300,000 people were in danger during each of these disasters. But about 230,000 people died in the Sumatra tsunami, whereas an estimated 16,000 died in Japan, according to Vasily Titov, an oceanographer at the NOAA Center for Tsunami Research in Seattle. The difference came down to tsunami education programs and warning systems in Japan, Titov said. "About the same amount of people were exposed for both events, but 10 percent of them died in Japan and about 90 percent were killed in Sumatra," Titov told Live Science.

Fewer people died in Japan because "everyone is very much in tune with the tsunami hazard," and hundreds of thousands of people evacuated to shelters during and after the catastrophe, he said.

Tsunami readiness may help save lives in the future. Nowadays, people who live on the coastlines of large bodies of water, especially the Pacific and Indian oceans, are at risk, and these populations are only growing. In 2000, about 625.2 million people worldwide lived in low-elevation coastal zones, according to a 2015 study published in the journal PLOS ONE. The researchers estimated that between 879 million and 949 million people will live in these low-elevation areas by 2030, making tsunami education and warning systems paramount.

But preparedness appears to be paying off. In 2010, an 8.8-magnitude earthquake in Chile triggered a tsunami, and together, the earthquake and tsunami killed about 500 people. The tsunami was responsible for fewer than 200 of the deaths, Titov said. In 2015, an 8.3-magnitude earthquake in Chile also triggered a tsunami, but the country immediately evacuated about 1 million people away from the coastline, and only five people died in the catastrophe, Titov said.

To survive a tsunami, create a safety kit and plan, so you and your family know where to meet and how to evacuate to higher ground, Ready.gov advises. Also — needless to say — stay away from the beach.

Unlike for tsunamis, there is no warning system for earthquakes. But few large tremblors have struck populated areas of the United States in recent years. A total of eight people died from earthquakes from 1999 to 2014 in the United States, the CDC reported. Worldwide, earthquakes have killed tens of thousands of people. An estimated 629 people died from earthquakes in 2012; about 22,000 in 2011; and 320,120 in 2010, largely from the 7.0-magnitude earthquake in Haiti, according to the U.S. Geological Survey.

Avalanches and landslides also caused havoc. A total of 549 people died in these natural disasters from 1999 to 2014 in the United States. The deadliest year was 2014, with 85 deaths, including 43 from the catastrophic landslide in Oso, Washington.

Earth could also experience extraterrestrial threats from asteroids. After all, an asteroid is thought to have wiped out 75 percent of all species (including the dinosaurs) about 65 million years ago, at the end of the Cretaceous period. But no human death ever recorded was due to an asteroid, so it's hard to give the odds of dying from one of these space rocks, said Lindley Johnson, NASA's planetary defense officer. (A meteorite was thought to have killed a man in southern India on Feb. 6, 2016, but NASA has since reported the event was more consistent with a land-based explosion than a space rock.) [When Space Attacks: The 6 Craziest Meteor Impacts]

"It is so rare, there has never been a scientifically confirmed report of someone being killed by a meteorite impact in recorded history," NASA's Planetary Defense Officer Lindley Johnson told Live Science in February. "There have been reports of injuries, but even those were extremely rare before the Chelyabinsk event three years ago."

Lightning is far more deadly, with 25 people getting zapped by a bolt in the United States in 2014. Cataclysmic storms (such as hurricanes, tornadoes, dust storms and tidal waves — which are shallow water waves) are even worse, killing 61 people in the country in 2014.

So take precautions, caring for your health and your safety, lest you become a statistic. But don't stress about the freak events — odds are, you'll die of something much more mundane.

Editor's Note: This story was first published in 2005 and has been updated with the most recent data. Live Science will continue to update the odds of dying as new numbers are released.

Follow Laura Geggel on Twitter @LauraGeggel. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

Severe floods in Texas and Oklahoma are causing devastation after multiple storm systems battered a formerly drought-stricken area, according to experts.

Heavy rainfalls began on Saturday (May 23) and soaked the region through the weekend, leading to nearly record-breaking rains in some southern areas of Texas and Oklahoma. Flash flooding and tornadoes have also been reported in certain cities and towns. At least 10 people have been reported dead across Oklahoma and Texas, and thousands have been evacuated from their homes and are seeking temporary shelter.

These catastrophic conditions are being caused by an El Niño pattern — a natural climate cycle that brings warmer-than-average temperatures to the Pacific Ocean — that has split the jet stream into two branches, with one river of air going off north and the other one sinking farther to the south, said John Gresiak, a senior forecaster for AccuWeather. It is the southern stream that is causing the disturbances in Texas and Oklahoma, after passing through California and Mexico, he added. [Fishy Rain to Fire Whirlwinds: The World's Weirdest Weather]

"Just looking at San Antonio, as of this date they've had double their rainfall for May, and they'll probably get more," Gresiak told Live Science.

The area has been experiencing severe drought for about five years, so residents are no longer used to the large amounts of rainfall that typically fall at this time of year, said Walt Zaleski, the warning coordination meteorologist for the regional headquarters of the National Weather Service (NWS) in Fort Worth, Texas.

"It's not out of the ordinary for us to be getting severe storms that produce thunderstorms and hail," he told Live Science.

While this "drought-buster" rainfall is a welcome relief to cities that had been facing lower-than-usual reserves, the amount of rain that has come all at once has been difficult for residents to deal with, he said. In just four months, the water has replenished lakes that were previously 20 to 25 feet (6 to 8 meters) below normal levels.

Flash flooding, which occurs suddenly when an intense amount of rain falls over a short period of time, has also been an issue. In Wimberley, Texas — a town just southwest of Austin — the Blanco River rose to 40 feet (12 m) from 9 feet (2.7 m) in just 2.5 hours, Zaleski said.

There won't be a reprieve yet from the water, as severe storms are expected to remain in the forecast. For the next couple of days, however, meteorologists at the NWS are expecting the worst of the storms to hit west of Texas, where fewer people live. Regions that are farther east may get battered again with severe weather toward the end of the week, Gresiak said.

Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

This story was updated on April 9 at 9:48 a.m. ET.

A wide swath of the central United States is at risk of thunderstorms and possible tornadoes over the next couple of days, according to the National Weather Service.

There is severe weather forecasted today (April 8) in two regions of the Midwest and Plains states: from east Indiana to West Virginia, and central and north-central Missouri. Storms are also developing in western Oklahoma, though they're not severe yet, and meteorologists are predicting more moderate risks in north-central Oklahoma, southeast Kansas and western Missouri. 

Tomorrow's forecast is still in flux, but damaging winds could blow through parts of Lower Michigan, western Pennsylvania, northeast Texas and southern Wisconsin, experts say. [50 Amazing Tornado Facts]

Greg Carbin, a warning co-ordination meteorologist at the National Weather Service's Storm Prediction Center, warned that the complexity of the current forecast means predictions could change quickly. He urged residents in the affected areas to check weather forecasts frequently for the latest information.

"It's a tough, tough forecast, not just for today but also for tomorrow," Carbin told Live Science. "Tomorrow may be more difficult due to this transition that may occur from loosely organized groups of thunderstorms to some severe weather potential."

Science of forecasting

While storm forecasts are not exact yet, they have vastly improved over the past couple of decades. That's because there are more satellites in orbit now and computing power has greatly improved, Carbin said.

More global models are available as well, making it easier to see how weather in one region affects another. In the case of tornado predictions, the first thing forecasters first look for is the potential for thunderstorms. That's because tornadoes can only occur if thunderstorms happen first.  "You can't have one without the other," Carbin said.

Thunderstorms require three ingredients:. The first is moisture, which acts as fuel for the storm; it occurs as moist air rises and cools to condense into rain. Another factor is known as instability, which refers to the temperature difference in a vertical column of air — the greater the temperature difference, the faster the air rises. Finally, something is must lift the atmosphere, such as a mountain range or heating.

A severe storm, sometimes with a potential for tornadoes, is defined as one with hail measuring more than an inch (2.5 centimeters) across and/or wind gusts in excess of 60 mph (97 km/h). Wind shear (the difference in wind speed or direction with increasing altitude) helps thunderstorms persist, Carbin said.

Staying safe

Stormy weather in the central United States is not unusual for this time of year, but Carbin said the key to staying safe is knowing where you are situated in your community and when severe weather is likely to hit. Most storm predictions are specific to a certain region, so it's important to know what county you are in, and the basic geography of your surrounding area.

"That kind of information is crucial, so you can get the warning," Carbin said.

If you follow alerts closely, he said, you should be able to get to safety. Carbin recommends staying in a sturdy building with "as many walls as possible" between you and the outside weather, if a basement is not available.

If you find yourself on the open road during severe weather, Carbin said most tornadoes move from west to east. As such, he recommends staying to the south and east of any storms you see.

Up-to-date forecasts can be found on the National Weather Service's website.

Editor's Note: This story was updated to correct the spelling of Greg Carbin's last name.

Follow Elizabeth Howell @howellspace, or Live Science on Twitter @livescience. We're also on Facebook & Google+. Original article on Live Science.

After some of the quietest three months of a U.S. tornado season in 60 years, severe thunderstorms and tornadoes ripped through Oklahoma and Arkansas yesterday.

A damaging tornado touched down outside Tulsa, Oklahoma, last night (March 25). One person was killed and several were injured when the tornado destroyed a mobile home park. A small twister was also reported in Moore, the Oklahoma City suburb that has been repeatedly ravaged by deadly twisters this decade.

The two weak tornadoes ended a long dry streak for the 2015 tornado season. For only the second time since the 1950s — when good record keeping began — the first three weeks of March were tornado-free throughout the United States, according to the National Weather Service's Storm Prediction Center in Norman, Oklahoma. A typical March sees about 120 twisters, the center reports. (Only March 1969 compares, without a single tornado until the 24th.) [The Top 5 Deadliest Tornado Years in U.S. History]

This is also the third March in a row with a low tornado count, the Storm Prediction Center reports. In March 2014, there were only 20 tornadoes, and March 2013 had 18 reported tornadoes. The lowest U.S. March tornado count was six, in 1951, though some tornadoes may have been missed because there was no Doppler radar yet.

So what's making tornadoes shirk the United States this year? The oddly calm tornado season owes a debt to the weather patterns responsible for the East's cold, snowy spring and the West's warm, dry drought.

A high-pressure ridge centered over the northwest Pacific Ocean is sending the jet stream on a swooping arc across the United States that delivers cold, dry Arctic air directly to the East Coast. With these chilly blasts hitting Tornado Alley for most of January, February and March, conditions favorable for tornadoes simply haven't shown up, storm experts said.

"Creating a tornado is just like baking an apple pie: You need certain ingredients in the atmosphere to create a tornado, and those ingredients just aren't there," said Victor Gensini, a severe storms climatologist at the College of DuPage in Illinois.

Gensini said these same atmospheric patterns were in place in 2014, another year with a lower-than-average tornado count.

Severe thunderstorms require wind shear (differences in wind speed and direction over a short distance); a source of lift; atmospheric instability (such as cold, drier air above warm, humid air); and moisture.

This week, southerly winds drew warm, moist air northward into the Central Plains, where it collided with colder air, spawning severe winds, golf-ball-size hail and a handful of tornadoes.

With yesterday's storms now moving eastward, Gensini forecasts a return to a persistent calm pattern for the rest of March. "I don't think we will see a tornado watch for the rest of the month," he told Live Science.

But don't expect the quiet to last. Tornadoes can strike any time of the year in the United States, and April, May and June are the big months for twisters in Tornado Alley. "We really haven't gotten to the heart of severe weather season yet," Gensini said.

And over the past three years, there have been deadly tornado outbreaks in Oklahoma and Arkansas in April and May, despite the dearth of twisters in earlier months.  

Follow Becky Oskin @beckyoskin. Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.

This year's El Niño may not only bring a bit of drought relief to parched Western states, but also could deliver a quiet tornado season, a new study finds.

Much of the southeastern United States faces a lower risk of tornadoes during El Niño years, the new research shows. The effects are strongest in Oklahoma, Arkansas and northern Texas. Damaging hail is also less likely during a strong El Niño, researchers report today (March 16) in the journal Nature Geoscience.

"The cool thing is, you can actually forecast what the spring tornado season will be like," said lead study author John Allen, a severe weather climatologist at Columbia University's International Research Institute for Climate and Society in Palisades, New York. [The Top 5 Deadliest Tornado Years in U.S. History]

The team's experimental forecast for this March, April and June calls for a slightly lower risk of tornadoes due to this year's El Niño. There is a 60 percent chance of an average tornado year, a 30 percent chance of a below-normal year and a 10 percent chance of an above-average number of tornadoes, the researchers said. However, even a quiet year can see deadly twisters strike in the United States, Allen said. In 2013, a relatively quiet tornado year, a late May tornado outbreak killed dozens in central Oklahoma.

Tornado forecasts

Allen and his colleagues are part of a group of scientists who intend to start issuing seasonal tornado forecasts that are similar to the hurricane and seasonal outlooks issued by the National Oceanic and Atmospheric Administration (NOAA). The experts have been meeting yearly since 2012 to advance the science of forecasting tornadoes.

Currently, the National Weather Service's Storm Prediction Center issues tornado outlooks up to eight days in advance. In contrast, hurricane outlooks come several months ahead of the summer storm season.

However, though the Columbia University research team plans to issue its own forecast as soon as next year, optimistically, an official forecast is at least five years away, said Ashton Simpson Cook, a meteorologist at the Storm Prediction Center who was not involved in the research. "We've already started on it, [but] we're in the beginning phase," he told Live Science.

The new findings are based on a comparison of weather records during El Niño years versus La Niña years. The authors did not use historical tornado records, which are fraught with reporting biases. Instead, they analyzed the environmental conditions that favor severe weather, such as temperature, atmospheric moisture and wind shear, which is different wind directions and speeds at different elevations above the surface. Then, the team created a forecasting formula that linked wintertime El Niño-La Niña conditions to the probability of severe storm activity in the following months.

"This is a great study," Cook said. "It's the next step in assessing the role of ENSO [El Niño] on severe weather, not just tornadoes."

Warm ocean, few tornadoes

The El Niño-La Niña cycle, or ENSO, is a natural climate pattern in the Pacific Ocean. During an El Niño, warm sea surface temperatures spread across the tropics. In a La Niña year, the opposite happens: Cool sea surface temperatures dominate in the eastern tropical Pacific. These temperature shifts have a ripple effect on wind patterns around the world, which, in turn, affects where storms form. [Fishy Rain to Fire Whirlwinds: The World's Weirdest Weather]

NOAA declared El Niño’s arrival last week, after Pacific Ocean sea surface temperatures crossed a warm threshold and wind patterns shifted in response.

So far, the 2015 tornado season is off to a slow start, with 28 tornados reported, according to the Storm Prediction Center. However, Allen said the cold weather across the eastern United States likely had a stronger effect than El Niño conditions on suppressing tornadoes so far this winter.

In an El Niño year, the jet stream is more southerly, which tamps down the wind patterns that generate severe storms. (For instance, the southerly flow brings cool, dry air from the plains and Canada.) The weather patterns that form twisters and hail decreased by 25 to 50 percent during an El Niño, the study reported.

During a La Niña year, the jet stream across North America shifts to the North, which favors more tornadoes in the Southeast. This brings warm, moist air into Tornado Alley, the twister-prone regions of the United States. Tornado and hail activity doubled across Oklahoma, Arkansas and northern Texas during strong La Niña years, the researchers reported. The opposite pattern is seen in the Gulf Coast and Florida panhandle, with an increase in tornado activity during El Niño and a drop during La Niña years, the researchers also noted.

"There is a geographical dependence, which explains why it might be hard to untangle the impact if you were to just look at the total number of tornadoes [each year] in the U.S.," said study co-author Michael Tippett, a climate scientist at Columbia University.

Direct observations from earlier studies agree with the findings. For example, there were spikes in tornado activity during strong La Niña years, such as in 1999 and 2011. Strong El Niño years brought a drop in tornados, in 1969 and 1988.

Follow Becky Oskin @beckyoskin. Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.

The same loopy weather patterns directing California's ongoing drought and last year's deep freeze across the East Coast may also change how often tornadoes strike the southeastern United States, a new modeling study finds.

Researchers examined how global warming will affect severe weather during the heart of tornado season — March, April and May. They found that while the yearly tornado total will climb by 2080, the number of tornadoes will also vary wildly from year to year. That's because sometimes, the weather will get stuck in a pattern that favors tornadoes, and sometimes, conditions will stymie stormy weather, according to the report, published Jan. 15 in the journal Climatic Change.

"We see this trend in a lot of extreme weather," said lead study author Victor Gensini, a severe storms climatologist at the College of DuPage in Illinois. "Changes in the jet stream are causing the jet to break down and get stuck in these blocking patterns," Gensini said. "It just so happens it could be in a favorable pattern for tornadoes or a really bad pattern [for tornadoes]." [The Top 5 Deadliest Tornado Years in U.S. History]

In the future, tornado season will also peak earlier, in March instead of May, the study reported. The number of tornadoes in April will rise slightly, while May's total twister count will stay the same.

"Because of increasing temperatures, we'll have more [atmospheric] instability earlier in the year, and instability is the fuel for tornadoes," Gensini said.

Typically, climate models can't predict how global warming will affect tornadoes because the storms are smaller than the resolution of climate models. But Gensini's approach relies on a relatively new weather forecasting model that can recreate the hazardous storms that generate tornadoes, hail and damaging winds.

"This is a model that can see thunderstorms, and climate models don't know anything about thunderstorms," said Harold Brooks, a senior scientist with the National Severe Storms Laboratory in Norman, Oklahoma, who was not involved in the research.

Two major factors control the birth of a tornado: convective available potential energy, or CAPE, and vertical wind shear. The available potential energy relates to warm, moist air at low altitude and cold, drier air above. Combined with wind shear — big changes in wind direction and speed with height — these conditions can spawn rotating air that triggers a tornado.

The new model predicts that these severe weather conditions are more likely to occur in the future, at least during the months of March, April and May. The increases are seen primarily across the Mississippi, Tennessee and Ohio River valleys. Only northern Florida will see a drop in severe weather, the study reported.

"It will be really unlikely to get a tornado in Florida in March, April or May," Gensini said.

At this time, the researchers don't know if the total number of tornadoes will shift during other months, Gensini said. Tornadoes can strike at any time during the year.

The variability from year to year is "a really intriguing result," Brooks said. A study published last year by Brooks found that tornado years are more variable than they used to be, and tornadoes cluster together more often.

In 2011, there were 1,894 tornados — many of them deadly, including the Joplin, Missouri, twister that killed 161 people. That tornado total was followed by a sharp decline, with 1,119 tornadoes in 2012; 943 in 2013; and 1,057 in 2014, according to the National Weather Service.

Follow Becky Oskin @beckyoskin. Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.

One of the deadliest tornado outbreaks in U.S. history was strengthened by smoke from burning farmlands in Central America, a new study suggests.

On April 27, 2011, some 200 terrifying twisters touched down across the Southeast — the most on record in a single day. Damages topped $11 billion, and 316 people died. (The devastation on April 27 was the worst of a four-day tornado outbreak spanning April 25 through April 28.)

The hardest hit states were Mississippi, Alabama, Tennessee and Georgia, which were struck by 15 tornadoes ranked EF-4 or higher on the Enhanced Fujita Scale. There were also four powerful EF-5 tornadoes — the highest possible tornado ranking — as severe storms raked through these states. [Destructive U.S. Tornadoes of April 2014: Gallery]

Researchers now say that air pollution intensified this incredible tornado outbreak. When supercell storms on April 27, 2011, mixed with smoke in the air, the volatile combination boosted the conditions that trigger tornados, according to a study published Jan. 26 in the journal Geophysical Research Letters.

However, the study notes that the twisters were primarily caused by the storms, not by smoke. "The smoke is not responsible for this outbreak," said Pablo Saide, lead study author and a postdoctoral researcher at the University of Iowa's Center for Global and Regional Environmental Research. "The main driver is the environmental conditions — the temperature and the wind profiles."

During the tornado outbreak, a satellite recorded high levels of smoke drifting across the Gulf of Mexico from burning fields in eastern Mexico and the Yucatan Peninsula. (Pollution from agricultural burning is also a concern in the United States, where several states have regulated the practice under the Clean Air Act of 1990.)

The pollution included soot and aerosols, which are fine particles and droplets suspended in the air. In the new study, the researchers looked at what effects these pollutants may have had on the birth of tornadoes, using a climate model. The researchers found two main effects, which required aerosols to be both close to the Earth's surface and above the cloud layer, Saide said.

One effect was that the aerosols brightened clouds in a way that increased wind shear (vertical differences in the speed and direction of the wind) and lowered the cloud base. The second effect was that the dark soot in the smoke warmed cloud tops, just like the sun does to a dark car. This effect boosts temperature contrasts between the top and bottom of the storm clouds, making it harder for different layers of air to mix. All of these factors tend to make tornadoes stronger and more likely to develop, Saide said.

About 90 percent of the supercell storms on April 27 produced at least one tornado, compared with the typical rate of about 25 percent, according to a study published in July 2014 in the Bulletin of the American Meteorological Society. 

Climate scientist James Elsner, who was not involved in the research, said the study is provocative, but he noted that some effects attributed to the pollutants could actually be independent of aerosols. "I think the increased wind shear is certainly reasonable, but cloud heights are always pretty low across Mississippi and Alabama, so that seems pretty dubious," said Elsner, a professor at Florida State University in Tallahassee who recently published a study on tornado clusters.

The researchers now plan to test their model on other historical tornado outbreaks. "Clearly, we need to know if this is more robust," said study co-author Greg Carmichael, a professor of chemical and biochemical engineering at the University of Iowa.

Testing the effects with climate models that add smoke to large-scale storm simulations could further explain how aerosols enhance tornadoes, said Victor Gensini, a severe-storms climatologist who was not involved in the study.

"This is just one case, but it could definitely be a piece of the puzzle in creating the environment that you need for a tornado," said Gensini, an assistant professor at the College of DuPage in Illinois.

Editor's note: This story was updated Feb. 5 to correct the spelling of Victor Gensini's name.

Follow Becky Oskin @beckyoskin. Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science .

NEW YORK — From the eruption that buried Pompeii in A.D. 79 to the superstorm that shut down New York City in 2012, natural disasters are an unavoidable part of life on Earth. Once thought to be the wrath of the gods, these formidable events now have widely accepted scientific explanations.

A new exhibit at the American Museum of Natural History (AMNH) explores the causes and aftermath of the mighty forces that shape the planet, from earthquakes to volcanoes to hurricanes.

The interactive exhibit lets visitors build their own virtual volcano, create and measure tiny earthquakes, and see what the eye of a tornado looks like. "Nature's Fury: The Science Behind Natural Disasters" will be open to the public from Nov. 15 to Aug. 9, 2015. [See more photos of natural disasters]

"For all time and in all places, people have sought to explain powerful natural phenomena, like hurricanes, floods, volcanoes, avalanches, wildfires, earthquakes and tsunamis," AMNH President Ellen Futter said Wednesday (Nov. 12) at a news briefing here at the museum.

The exhibit reveals how scientists study natural disasters, what they can learn from them and how that knowledge can help communities prepare for and adapt to these forces of nature.

"This is even more crucial in a time of tremendous environmental and climate change, when forces that scientists are actively trying to understand are having an impact on the degradation of the environment faster than we can keep up," Futter said.

Earthly rumbles

Earthquakes are some of the most destructive and least predictable natural phenomena. The new exhibit reveals how earthquakes occur along faults where tectonic plates move against each other. When that stress gets too high, the fault ruptures, producing a shock wave that can cause major disasters such as the San Francisco earthquake of 1906 that reportedly killed at least 3,000 people.

"We cannot predict earthquakes, and that is a scientific problem of the first order," exhibit curator Edmond Mathez, of the museum's Department of Earth and Planetary Sciences, told reporters at the event. What we can do, Mathez said, is "say something about the probability of an earthquake of a certain size occurring in a certain area over a certain time." [Top 10 Deadliest Natural Disasters in History]

Visitors can create their own tiny earthquake by stomping or jumping next to a seismometer, a device that measures the magnitude of an earthquake on the Richter scale. Each increment on the scale corresponds to a release of 10 times as much energy as the previous increment.

Powerful earthquakes sometimes also generate tsunamis. In 2004, for example, a 9.3-magnitude earthquake in the Indian Ocean triggered giant waves along most of the surrounding coastlines, which killed more than 230,000 people. The exhibit emphasizes the need for tsunami warning systems to help communities prepare for such devastating events, and the importance of cultural practices that can help the affected people recover.

Volcanic wrath

Few phenomena sculpt the Earth more visibly than volcanoes. More than 75 percent of the world's volcanoes lie along a 25,000-mile (40,200 kilometers) arc around the Pacific Ocean, called the Ring of Fire. When these volcanoes  erupt, the outbursts can have far-reaching effects on the planet's climate.

If you were to put a wall around Central Park and fill it to a height of more than 4 miles (7 km), that's how much magma is moving through the Earth toward the surface every year, said James Webster, a volcanologist and curator for earth and planetary sciences at the museum.

Webster simulates volcanic conditions in his lab, by superheating crushed lava rock inside a powerful oven. It's one of only two such labs in the world, according to members of the museum's staff.

Nature's Fury explores some of the most notorious volcanic eruptions in history, from Mount St. Helens in 1980, to Mount Vesuvius in A.D. 79, to Mount Pelée on the island of Martinique in 1902. Some volcanoes, such as the supervolcano beneath Yellowstone National Park, haven't erupted for hundreds of thousands of years, but they can — and likely will — erupt again one day.

An interactive simulation lets visitors "build" their own volcano by adjusting levels of gas and silica, which influence how explosive an eruption will be. For example, stratovolcanoes erupt violently in a cloud of ash, whereas shield volcanoes erupt in gentle, flowing mounds.

Terrifying twisters

Fans of the 1996 movie "Twister" are familiar with the fearsome power of tornadoes. These violently rotating columns of air form when warm, humid air collides with cool, dry air to create thunderstorms. About 75 percent of tornadoes occur across eight U.S. states, in a region known as Tornado Alley.

The new exhibit explains how scientists, dubbed storm chasers, use probes to measure the wind speeds, air pressures and other parameters inside a tornado, which can help meteorologists predict a storm's severity and issue warnings to the public. [In Images: Extreme Weather Around the World]

Storm chaser Tim Samaras captured video footage of atornadonearStormLake,Iowa, from a special probe attached to the ground. A panoramic screen gives museum visitors a view from the inside of the twister.

Horrific hurricanes

Finally, the museum takes visitors on a tour of hurricanes (also known as cyclones or typhoons). These powerful storms, with winds of at least 74 miles per hour (120 km/h) usually form in the tropics. The exhibit describes the deadliest natural disaster on record in U.S. history, an unnamed hurricane that hit Galveston, Texas, in 1900 and killed 8,000 people.

Since then, scientists have learned a lot more about forecasting hurricanes, though the storms can still wreak havoc on communities.

The exhibit has an interactive map of New York City during Hurricane Sandy in 2012, which shows the coastal areas that were most vulnerable to storm surges. The display also shows the city's efforts to mitigate damage from other massive storms in the future.

Follow Tanya Lewis on Twitter. Follow us @livescience, Facebook& Google+. Original article on Live Science.

From earthquakes to volcanic eruptions to hurricanes, natural disasters reveal the fearsome power of Mother Nature. Scientists are studying these phenomena to better understand them and find better ways to predict and prepare for them. Here are some photos of nature's fury. [Read full story about the science of natural disasters]

1906 San Francisco earthquake

The earthquake that hit San Francisco on April 18, 1906, was one of the most significant earthquakes in history. Caused by a rupture along the northern section of the San Andreas fault, the quake caused a raging fire in San Francisco. The quake killed at least 3,000 people, according to the U.S. Geological Survey. (Image © Library of Congress)

Sloping building on car

The Loma Prieta earthquake hit northern California on October 17, 1989. San Francisco's Marin District was one of the hardest hit by the estimated 6.9-magnitude quake, as shown by this car crushed by a collapsed house. (Image © Adam Teitelbaum/AFP/Getty Images)

Indian Ocean tsunami

In 2004, a 9.3-magnitude earthquake in the Indian Ocean triggered giant waves along most of the surrounding coastlines, killing more than 230,000 people. Here, people flee a tsunami at Koh Raya, in Thailand's Andaman Islands, on Dec. 26, 2004. The photographer who took the picture managed to escape unharmed as he retreated from the first wave. He stood watching as a second wave tore up the wooden buildings, and a third wave ripped apart the cement buildings "like they were made of balsa wood." (Image © John Russell/AFP/Getty Images)

Erupting volcano

Hawaii's Kilauea volcano, located on the southern shore of the Big Island, has been actively erupting for decades. Shown here is Pu’u ‘O’o, a typical cinder cone spattering a fountain of lava in irregularly shaped globs that fall down in a heap around the vent. (© United States Geological Survey; Photo by G.E. Ulrich)

Mount St. Helens

The explosive eruption of Mount St. Helens in the spring of 1980 produced a ball of ash rising through the clouds, as shown in this photo taken on July 22 of that year. The eruption blasted off the top portion of the volcano. The volcanic activity is caused by the subduction of the Juan de Fuca plate off the western coast of North America. Scientists say Mount St. Helens is the most likely volcano in the continental United States to erupt again in the future, according to the USGS. (Image © United States Geologic Survey; Photo by Jim Vallance)

Hurricane Dean

Hurricane Dean was the strongest hurricane of the 2007 Atlantic hurricane season. It struck downtown Kingston, Jamaica on August 19, 2007, battering the city's waterfront boulevard with strong winds and heavy rains. (Image: © Andres Leighton/AP Photo)

Campo tornado

About three quarters of all tornadoes take place in a part of the central United States known as Tornado Alley. The violent winds and funnel-shaped clouds are formed when warm, humid air from the Gulf of Mexico meets cool, dry air from the north, producing thunderstorms. The conditions create an average of 600 tornadoes per year. This 2010 tornado touched down in Colorado and swept into Oklahoma. (Image: © Willoughby Owen)

Shake-it-up interactive

A new exhibit at the American Museum of Natural History, in New York City, lets visitors stomp on the floor next to a seismometer, a device that measures the magnitude of an earthquake on the Richter scale. Each increment on the scale corresponds to a release of 10 times as much energy as the previous increment. (Image: © AMNH/R. Mickens)

Build-your-own-volcano

Museum visitors can also create their own virtual volcano. By adjusting the levels of gas and silica in the volcano's lava, they can create different types of volcanoes. More silica results in more viscous and gooey lava, whereas more gas makes an eruption more explosive. (Image: © AMNH/D. Finnin)

Stand in the eye of a tornado

In this tornado exhibit, visitors can experience what it looks like inside the eye of a tornado. Storm chaser Tim Samaras captured this unique footage of a tornado near Storm Lake, Iowa, from a special probe attached to the ground. (Image © AMNH/M. Shanley)

Hurricane Sandy interactive

The exhibit also contains an interactive map of New York City showing its 520 miles (837 kilometers) of coastline (longer than the coastlines of Miami, Boston, Los Angeles and San Francisco combined). The exhibit shows the parts of the city that were most vulnerable to Hurricane Sandy's storm surge in 2012, and includes some of the efforts being made to mitigate the effects of future storms. (Image: © AMNH/D. Finnin)

Follow Tanya Lewis on Twitter. Follow us @livescience, Facebook & Google+.

Tornadoes are touching down in clusters more often than 50 years ago, a new study reports. On some days, more than 30 twisters strike the United States.

Even as storms spawn more tornadoes, there are fewer days on which tornadoes occur, according to the study, published today (Oct. 15) in the journal Science. Since the 1970s, the number of days with at least one EF-1 tornado has dropped from a mean (or average) of 150 to 100.

"When people ask, 'Are we getting more tornadoes, are we getting fewer tornadoes, are they later, are they earlier?' — the answer to everything is yes," said lead study author Harold Brooks, senior scientist at the National Oceanic and Atmospheric Administration's Severe Storms Laboratory in Norman, Oklahoma.

While it's clear that something about tornados in the United States is changing, there is no strong evidence that climate change is to blame.

Brooks said the study is a first step toward exploring possible links between new tornado patterns and global warming. "Obviously, we've had a change in the frequency of the number of days of tornadoes, and in some sense that's a reflection of the climate being different than it was," he told Live Science. "But we don't have the primary cause and effect yet." [The Top 5 Deadliest Tornado Years in US History]

Climate change assist?

Tornadoes are born from severe thunderstorms that feed on warm, moist air and from strong winds that change direction with altitude (called wind shear), which rotate the storms. While global warming is expected to increase the atmospheric fuel available for severe thunderstorms, some scientists think the same conditions may also bring weaker wind shear, resulting in a stalemate. However, a climate-modeling study from Stanford published last year contradicts this idea, finding strong wind shear is especially likely in the spring (peak tornado season in the South) as temperatures rise across the United States.

"The climate change signal may be hidden in this idea of more concentrated tornadic activity," said James Elsner, an atmospheric scientist at Florida State University in Tallahassee, who was not involved in either study. Elsner published a similar analysis of U.S. tornado data in August in the journal Climate Dynamics. He concluded that tornadoes are both growing stronger and increasingly arriving in clusters, even as the total number of days with tornadoes held steady.

Brooks and his co-authors documented the shift toward multiple tornado outbreaks by looking at tornadoes of EF-1 intensity and greater between 1954 and 2013, using official tornado records from U.S. Storm Prediction Center.

The Enhanced Fujita scale, or EF scale, ranks tornadoes based on wind speeds and damage. A tornado with wind speeds between 86 and 110 mph (138 and 177 km/h) is usually rated an EF-1. The highest rating is an EF-5. [See the Tornado Damage Scale in Images]

The yearly tornado total has remained stable over time, the researchers discovered. The mean annual rate of tornadoes rated as EF-1 and greater held steady at 495 per year since the mid-20th century, though the total count can swing wildly. The record high, in 2011, was 898 tornados, and the record low, of 311 tornadoes, was recorded in 2002.

Rising risks

Yet even as yearly tornado tallies remained steady, the nature of tornado outbreaks has changed. Now, there are long dry spells between days of terror when huge numbers of tornadoes rack up the yearly count. For example, in 1973, most of the year's tornadoes were spread among 187 tornado days, and only two days had more than 30 tornadoes. But in 2011, there were nine days that had more than 30 tornados, with only 110 tornado days.

The start of tornado season is also changing, lurching back and forth across its March 22 kickoff, the researchers report. The latest and earliest tornado season starts all took place since 1999.

Tornadoes have always had an element of unpredictability, but forecasting technology is keeping up with the new normal, scientists say. "The weather service is now able to pinpoint their [tornado] watches and warnings, make a more specific regional forecast, and cut down on false alarms," Elsner said.

Tornado clusters may have the biggest impact on emergency responders and insurers, who must adjust to covering severe damage across one or more states. "If you have a lot of events, you have to have the resources available to respond to those events," Brooks said. "If the ordinary events don't happen as often, your emergency response stuff is going to sit around, but you're still going to need all of it. That's a lot of power poles to keep stacked around."

Email Becky Oskin or follow her @beckyoskin. Follow us @livescience, Facebook & Google+. Original article on Live Science.

The busiest part of tornado season is happening up to two weeks earlier than it did 55 years ago, finds a new study on Tornado Alley, located in the heart of the central and southern U.S. Great Plains.

Tornado Alley is known for its destructive tornadoes, the strongest of which touch down between early May and early July every year.

Tornado reports from Nebraska, Kansas, Oklahoma and northern Texas show that peak tornado activity moved about seven days earlier from 1954 to 2009. When the researchers analyzed tornadoes on a state-by-state basis, they found that some states experienced peak tornado season an average of 14 days sooner in 2009 compared with 1954. [50 Amazing Tornado Facts]

"If we take Nebraska out [of the data], it is nearly a two-week shift earlier," lead researcher John Long, a research scientist in the department of land resources and environmental sciences at Montana State University in Bozeman, Montana, said in a statement.

The analysis shows that peak tornado activity moved about 1.55 days earlier each decade. At the heart of Tornado Alley, the peak of tornado season now typically occurs on May 19, as opposed to May 26 in the 1950s, the researchers found.

For the analysis, the researchers used the original Fujita scale of tornado strength, rather than the newer Enhanced Fujita scale, because the latter scale was not implemented until 2007 and thus would not be able to cover the majority of the years in the study.

For tornadoes rated as F1 and above on the original Fujita scale of tornado strength, the peak of tornado activity is also about 14 days sooner than it was 55 years ago, according to a preliminary analysis that the researchers did not include in the study.

Winds in F1 tornadoes on the original Fujita scale race between 73 and 112 mph (117 and 180 km/h). In contrast, F5 tornadoes blow between 261 and 318 mph (420 and 511 km/h).

"From a public safety perspective, if this trend (of an earlier tornado season) is indeed occurring, then people need to begin preparing for severe weather earlier in the year," Greg Carbin, the warning coordination meteorologist at the Storm Prediction Center in Norman, Oklahoma, said in the statement.

The new study does not attribute the windy shift to any one factor. The earlier tornado season, however, is in line with consequences expected of a warmer climate, the researchers said.

"If winters are not as cold, or if springtimes are warmer, the location of the jet stream is most likely displaced north of where it has been in the past," said Carbin, who was not involved in the new study. If the jet stream moves north, it can pull warm and humid air over the Midwest, where the hurricanes form. Warmer springs can cause tornado activity to happen earlier in the year, as is seen in the new study, he added.

Interestingly, earlier tornados in Oklahoma may also be linked to El Niño, which is associated with warm waters in the Pacific Ocean changing the air-surface pressure and atmospheric circulation. When El Niño conditions happened between January and April, high tornado activity also occurred earlier in the spring, the researchers found.

"The relationship we do see in Oklahoma is a light but significant connection to El Niño," study researcher Paul Stoy, an assistant professor in the department of land resources and environmental sciences at Montana State University, said in the statement. "This makes one suspect that if global climate change is changing these larger circulations, then there is a connection between a global [variability] and tornado activity.”

Still, the tornado records date back only to the 1950s, making it difficult for scientists to study long-term shifts. Also, regional factors, such as the topography of the land and areas where cool air mingles with warm air, can influence tornado formation, the researchers said.

The new study could help Tornado Alley residents know when to prepare for tornadoes, Long said. Every year, about 1,300 tornadoes hit the United States, killing about 60 people, according to the National Weather Service's Storm Prediction Center. In 2014, most of the 209 tornadoes that hit the United States happened in May, and the deadliest storms were in April, the center reported.

The study was published online Sept. 10 in the journal Geophysical Research Letters.

Follow Laura Geggel on Twitter @LauraGeggel and Google+. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

Less means more, when it comes to tornadoes in the United States.

There are fewer days with tornadoes compared with 60 years ago, but when storms do hit, there are more tornadoes per day, according to a study published Aug. 6 in the journal Climate Dynamics.

"We may be less threatened by tornadoes on a day-to-day basis, but when they do come, they come like there's no tomorrow," lead study author James Elsner, a climate scientist at Florida State University in Tallahassee, said in a statement.

Elsner and his co-authors analyzed historical tornado records from the National Weather Service from 1950 to 2013. [The Top 5 Deadliest Tornado Years in U.S. History]

The study is one of the first to find a clear trend of any kind in the tornado numbers. And, in fact, the team did not find a long-term change in the total number of tornadoes from year to year. While the total number of twisters each year can vary considerably, about as many tornadoes per decade hit in the 2000s as in the 1950s and 1960s.

So, what's the big change?

Specifically, the researchers found that the number of days with a tornado stronger than EF-1 on the Fujita ranking scale started dropping in the 1970s. In 1971, there were 187 EF-1 tornado days. In 2013, one of the quietest tornado years on record, there were only 79 EF-1 tornado days. (There's no distinct pattern to when the storms hit — tornadoes can strike any time of the year.)

Also, days with more than one EF-1 tornado are becoming more common, the researchers found. This increase accounts for the steady trend in the total number of tornadoes.

Looking at days with four, eight, 16 or 32 EF-1 tornadoes, the researchers discovered an uptick starting in the 1980s. One of the most significant increases was that the odds of having a day with 32 tornadoes doubled. And since 2001, every year has experienced a day with at least 32 EF-1 tornadoes, the study found. Before 1990, most years had no days with more than 32 tornadoes.

As the number of tornadoes per day increased, the risk of tornado clustering— in which groups of four or more tornadoes touched down within a close geographic region — also rose, the researchers found.

"I think it's important for forecasters and the public to know this," Elsner said in the statement. "It's a matter of making sure the public is aware that if there is a higher risk of a storm, there may actually be multiple storms in a day."

The researchers think climate change has played a role in the shift in tornado frequency and storm strength documented in the study. However, they stop short of blaming any one cause. Rather, multiple effects — such as atmospheric warming and less wind shear (different wind directions at different heights) — could lead to smaller, but more active storms and, in turn, spawn multiple tornadoes.

The researchers recommended several lines of research to test their model, such as studying the environmental conditions that trigger tornado clusters.

How to count tornadoes

For more than a decade, researchers have sought to connect the dots between global warming and severe weather such as hurricanes, drought and tornadoes.

But tornadoes and climate change present a particularly thorny problem. That's because scientists must first overcome problems in their storm-tracking data. For example, the way that weather officials assess tornado damage has changed over time. Because of this change, comparing tornado data from the 1950s to data from the 2010s could produce false trends.

Here's an example: The number of reported tornadoes has increased, thanks to improved radar monitoring, so it seems like more tornadoes are forming now than 50 years ago. But that's not because of climate change; it's because radar systems are better at keeping an eye on storms.

To get around this problem, Elsner and his co-authors analyzed only tornadoes stronger than EF-1 on the Fujita scale. Weaker tornadoes may have gone unnoticed in the past, but EF-1 tornadoes were likely to have been noticed and reported, researchers think. On the other hand, comparing tornadoes by strength on the Fujita scale introduces a different problem: Tornadoes that hit before 1973 were ranked retroactively, based on photographs and news reports. With no eyewitnesses, the tornadoes might have a stronger ranking than they actually deserve.

Elsner said that a portion of the trends reported in the results could come from such changes in data collection.

Email Becky Oskin or follow her @beckyoskin. Follow us @livescience, Facebook & Google+. Original article on Live Science.

Tornadoes are as much of a given in the Midwest as cornfields and county fairs. In an average year, twisters kill 80 people and injure more than 1,500, so you can imagine the excitement when a physics professor proposed an end to the annual misery: three great walls, each about 1,000 feet (300 meters) tall, that could potentially block the deadly storms of Tornado Alley.

But the idea didn't impress meteorological scientists. Never mind the huge cost, ecological consequences and engineering difficulties involved in the scheme, weather experts say it just wouldn't work.

"The first time somebody mentioned it to me, I thought they were actually joking," said Paul Markowski, a professor of meteorology at Penn State. "There are crazy ideas that could at least work, and then there are crazy ideas that wouldn't even work theoretically." [5 Wild Weather Control Ideas]

Pie in the sky?

The basic goal of the proposal, put forth in the International Journal of Modern Physics B by Rongjia Tao, a physicist at Temple University, is to thwart the "violent air mass clashes" that spawn punishing tornadoes.

Tao envisions three east-west walls, one at the northern edge of Tornado Alley, maybe in North Dakota, another in the middle, perhaps in Oklahoma, and the last stretching across southern Texas and Louisiana. In theory, these barriers would stop the warm, moist air that flows north from colliding at high speeds with cold air flowing southward. (Tornado Alley refers to the stretch of land between the Rocky Mountains and Appalachian Mountains that's particularly prone to tornadoes.)

Tao said he got the idea while working as a professor at Southern Illinois University at Carbondale, where he studied the differences in tornado risk between nearby Washington and Gallatin counties. He theorized that Gallatin County was better protected from tornadoes thanks to a small range at its southern border known as the Shawnee Hills, which only reach about 820 feet (250 m) in altitude. He saw a parallel in the Jiang-Huai Hills of China, which only stretch about 984 feet (300 m) off the ground. According to Tao, the Jiang-Huai Hills and two other east-west mountain ranges make the plains of China largely tornado-proof. He thinks he could mimic that quiet landscape in the United States with artificial walls.

Scientists not involved in the study said Tao's proposal is based on outdated ideas about how tornadoes form and ignores important geographic features. 

"He's got the basics almost completely wrong," said Harold Brooks, a research meteorologist at the National Oceanic and Atmospheric Association's (NOAA) National Severe Storms Laboratory in Norman, Oklahoma. "The reason there are so many tornadoes in the central United States is southerly flow at the surface bringing warm, moist air northward, and westerly winds from the Rockies bringing relatively cool, dry air above that, not some surface 'air flow clash location.'"

Markowski also chafed at the notion that stopping "air mass clashes" could stop tornadoes. (In fact, he recently co-wrote a paper in the Bulletin of the American Meteorological Society that offers a long argument about why people should drop the term "clash of air masses" when explaining tornadoes.) Air masses clash all the time, and they don't always spawn tornadoes, Markowski told Live Science. What's more, tornadoes can develop even without an air mass collision. Rather, storms with tornado potential form when warm, humid air near the ground gets trapped under drier air. This instability can produce a spinning updraft of air, which sometimes leads to a tornado.

Semantics aside, the scheme ignores already existing east-west mountain ranges, such as the Wichitas, Arbuckles and Ouachitas in Oklahoma, Brooks said. And roving air masses that go on to seed tornadoes would be able to clear a wall of the size Tao proposed, other scientists said. 

"Air masses routinely pass over the Appalachian Mountains. This is true in winter, when the air masses are much colder and heavier than they are in the summer," said Matthew Parker, a storm researcher and associate professor at North Carolina State University.

One of Parker's graduate students at N.C. State, Brice Coffer, actually put Tao's proposal to the test in computer simulations. Coffer used the Weather Research and Forecasting Model, a system commonly used to make high-resolution thunderstorm forecasts, to re-create a storm that spawned deadly tornadoes in Oklahoma in May 2013. He watched how the storm virtually unfolded in three different scenarios: one with the type of walls Tao proposed, one control with no walls and one with 1.6-mile-high (2.5 km) walls — just to play devil's advocate. [Skyscraper Storms: 7 Big City Tornadoes]

Coffer found that the 1,000-foot walls had no significant impact on the formation of storms in the region; that simulation looked nearly identical to the control. The exaggerated, 1.6-mile walls, however, do block the air — but with unintended consequences.

"If you put a rock in a stream, the same type of thing happens," Coffer told Live Science.

If the rock is small enough, the water will just flow over the rock. But plop a big enough rock into the water, and the stream will just go around it on the sides. That's would happen with a mile-high wall. The air would move around it instead of over it, shifting the storms eastward to the Mississippi River Valley instead of the plains and turning much of Texas into a desert, according to Coffer's model. What's more, strong circulations would occur at the edges of the walls, producing landspout tornadoes, which don't emerge from a supercell like regular tornadoes do, Coffer found.

Coffer's work hasn't been put through a peer review yet, but he recently submitted it to the Electronic Journal of Severe Storms and Meteorology.

Tornadoes stopped cold

Despite advances in engineering and scientists' understanding of tornadoes, humans are still largely powerless against the threat of these natural disasters. One only needs to look at recent history for proof. The National Weather Service ranked 2011 the fourth deadliest year for tornadoes on record, with 550 deaths and 1,691 tornadoes reported across the country, including the catastrophic storm that hit Joplin, Missouri.

Tao, whose work was in part funded by a grant from the U.S. Naval Research Lab, said he hopes to do a field test with a small wall protecting a localized, high-risk area to prove his idea is feasible.

"Once this field test is successful, people will accept the idea, and the wall will be gradually extended to eliminate the major tornado threat for the entire Tornado Alley," Tao told Live Science in an email. He added that he welcomes comments of skeptics and hopes that his proposal will at least spur more research into tornado-stopping plans.

Tao isn't the first to come up with a tornado-blocking concept, and experts think there are more theoretically plausible options than physical walls. One possibility might be to kill tornadoes by freezing them.

"If you have a bad storm approaching and you could suddenly make the downdrafts of the storm really cold, it would probably have a disruptive effect," Markowski said.

Markowski doesn't expect to see something like that happen in his lifetime. Fast forward 1,000 years, however, and perhaps engineers will have the technology to make a giant refrigerator to cool a whole town by several degrees just before a tornado barrels in, he said.

But who knows what the future will hold? Just a few years ago, an inventor was awarded a patent for a scheme to send suicide drones into a tornado with an ultra-cold substance such as liquid nitrogen to thwart the storm.

Follow Megan Gannon on Twitter and Google+. Follow us @livescience, Facebook & Google+. Original article on Live Science.

School hallways may not be the best place to ride out tornados, despite a long-standing tradition of ducking and covering along corridors.

That's one of the lessons emergency managers have learned from recent devastating tornadoes, particularly the Moore tornado that hit this Oklahoma City suburb on May 20, 2013. Seven children died at Plaza Towers Elementary School when the EF5 tornado hit, tearing away the roof and collapsing hallway walls onto huddled students. The damage highlighted the unfortunate fact that many schools are simply not built for safety.

"I have walked through schools and left thinking, 'Please don't let a storm come anywhere near this building,'" said Andrea Melvin, the outreach programs coordinator for Oklahoma Climatological Survey and Oklahoma Mesonet. Few school architects consider weather safety in their designs, she told Live Science. [Photos: Aftermath of the Moore Tornado]

"School designs need to change," she said "We cannot continue to add more glass everywhere and expect to have safe areas for sheltering. We can’t build walls that are not connected to the roof and foundation."

Dangerous schools

Melvin and her colleagues, who presented findings about school readiness at the American Meteorological Society meeting in Atlanta on Feb. 3, are fighting to better prepare Oklahoma schools for severe weather. There are an average of 47 tornadoes in the state each year, according to the National Oceanic and Atmospheric Administration (NOAA), and the whirlwinds cause an average of three deaths each year.

Despite this danger, building codes are not designed to ensure that schools withstand the kinds of winds even the most modest tornado can muster. The standard is to build schools to resist 90-mph (145 km/h), straight-line winds. The weakest EF1 tornadoes can sustain gusts of up to 110 mph (177 km/h), and their rotational winds put more pressure on buildings than a straight-line wind of the same speed, Iowa State University engineer Partha Sarkar told Live Science in 2013.

"The buildings are simply not designed to withstand that level of wind," Sarkar said.

The Moore tornadoes have prompted changes to the codes. In March, Moore adopted codes requiring that all new homes stand up to 135-mph (217 km/h) winds. And an International Building Code update that goes into effect in 2015 will require safe rooms in schools in the regions around Moore. Those regions are prone to strong tornadoes, and the safe rooms in the area should be built to stand up to 250-mph (402 km/h) winds.

But existing schools have particular vulnerabilities. In urban areas, the schools are frequently under construction, because of expanding student populations, Melvin and her colleagues reported. Many rely on "portable classrooms," which are simply metal storage units that provide no shelter against strong winds. Building walls may consist of cinderblocks stacked upon each other with nothing reinforcing them, Melvin told Live Science. Requests for bonds to raise money for improvements must be placed before voters, who frequently vote down these initiatives.

Meanwhile, the architecture of many schools makes finding shelter difficult. Hallways are often on the exterior of the building, lined with glass windows. Schools built during the period when open floor plans were popular are often retrofitted with walls made of unreinforced sheet rock, which simply collapse once the roof is breached.

Even interior hallways can be dangerous if they have doors on either side. During the Joplin, Missouri, tornado of May 22, 2011, school hallways turned into wind tunnels, with huge chunks of debris blowing freely through Joplin High School and East Middle School. Fortunately, the tornado hit on a Sunday, so students were not present.

Keeping students safe

In the wake of the Moore tornado, the Oklahoma Department of Emergency Management has started a program called Safe Schools 101, which trains volunteer architects, engineers and emergency officials how to evaluate the safety of school structures. The first classes started in early 2014, and the eventual goal is to evaluate every school in the state.

In the meantime, Melvin said that school officials should take a hard look at their school's emergency plans. The safest shelters are interior rooms with strong connections between foundation, walls and roof — and no windows. Bathrooms and locker rooms can be good options, though basements may not be best due to water or gas lines.

Some schools — including the two being rebuilt in Moore — are equipped with safe rooms, and parents are increasingly pressuring school districts to provide these rooms for every student. Teachers surveyed by Melvin and her colleagues unanimously agreed that every school should have a safe room. Such an initiative would cost more than $2 billion, however, Melvin said. [Tornado Safety: Where to Go & What to Do]

Nevertheless, safe rooms can be the difference between life and death. A poster presented at the AMS meeting by the researchers quoted a teacher who did have access to one of these rooms.

"As a teacher taking shelter in an all-school safe room while the May 20, 2013, EF-5 tornado passed about a mile away, I felt safe and reassured that my students were not at risk, but also felt panicked and helpless knowing that my own children's lives and thousands of other students' lives were not protected as they huddled in bathrooms and under desks at their nearby schools," the teacher said.

Another teacher, who was sheltering in the hallway at Plaza Towers Elementary, where seven students died, described her experience in that school's hallway.

"We heard the roar coming closer and closer, and realization sunk into my mind that it was upon us," she said of the tornado. "The kids were screaming then. We were all praying. I had my arms around a fourth-grade boy who was screaming over and over, I want my momma, I want my momma. I told him I would be his momma for now and that I wouldn't let go of him."

Follow Stephanie Pappas on Twitter and Google+. Follow us @livescience, Facebook & Google+. Original article on Live Science.

Tornadoes and Waffle House, the venerable greasy spoon breakfast establishment that is a staple of Southeast highway stops, may not seem to have much to do with one another (except for their occurrence in the Southeast). But a map showing the highest concentrations of the restaurant by latitude, which has been making the rounds on Twitter, inspired one meteorologist to look at tornadoes in the same way.

“My mind works in interesting ways. I came across this graphic of Waffle Houses by latitude and it got me thinking about how I could use a similar map related to weather,” Tim Brice, who created the maps, told Climate Central. “The first thing that came to mind was to show the latitude (and the longitude) of tornado touchdowns.”

And that’s just what he did. Using data available from the National Weather Service’s Storm Prediction Center, Brice, a meteorologist with the NWS office in El Paso, Texas, sorted verified tornadoes by their latitude and longitude and came up with two bar graphs showing each, laid out over the proper coordinates on a U.S. map.

“I love a good map, so I took it as a challenge to come up with them,” Brice wrote in an email.

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The resulting graphics show pretty clearly where tornadoes are most common in the U.S. In the longitude map, a clear spike corresponds to the so-called Tornado Alley, stretching across the Plains states from the Dakotas down to Texas, with a second, smaller spike corresponding to Dixie Alley, covering much of the Southeast That incidentally corresponds with the biggest spike in Waffle House restaurants, proving the classic science proverb that correlation doesn’t always equal causation.

A third spike aligns with Florida and is likely due to a summertime spike in waterspouts and funnel clouds spun up by the strengthened sea breeze, said Harold Brooks, a tornado researcher and forecaster with the National Severe Storms Laboratory. The tornadoes that form in this manner in Florida aren’t fueled by supercell thunderstorms, the massive rotating systems that typically spawn tornadoes in main Alleys.

The latitude map also shows the northern and southern edges of the U.S. with relatively low tornado counts while the middle is where much of the action occurs, albeit with a slight dip near the dead center. That dip in the middle of this general peak could be explained by lower tornado occurrences that are seen in West Virginia and southern Missouri, Brooks told Climate Central.

Moisture coming up from the Gulf of Mexico, a key ingredient fueling the supercell thunderstorms that spawn tornadoes, generally runs up the eastern side of the Appalachian Mountains, with less moisture available to the west of the ridges, including in West Virginia. According to NOAA statistics using 1991-2010 as the reference period, Virginia sees 18 tornadoes a year on average while West Virginia sees only 2 tornadoes.

Southern Missouri tends to have fewer tornadoes due to a bit of a fluke in geography. In the early part of the tornado season, tornado activity tends to follow something of an L-shape from the Southern Plains up into the Midwest. As the summer wears on, activity shifts northward into the Northern Plains and the Midwest. Southern Missouri ends up in between these two areas, Brooks said.

Brooks, who looks at tornado data constantly for his job, didn’t think that the latitude and longitude maps showed anything new, and would’ve liked to have seen the two sets combined into a 2-D map, instead of two 1-D maps. But he allowed that for those who aren’t as steeped in the ins and outs of tornadoes, the maps could help illustrate tornado risk.

Brice plans to follow up these maps with similar ones, showing the occurrence of tornadoes by the EF-scale by latitude and longitude.

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Follow the author on Twitter @AndreaTWeather or @ClimateCentral. We're also on Facebook & other social networks. Original article on Climate Central.

This article was provided by AccuWeather.com.

Moore, Oklahoma, is no stranger to destruction. Notable tornadoes have struck the area in 1998, 1999, 2003 and 2010. The May 20, 2013, tornado has the people of Moore working to restore what was demolished, and this time the city is rebuilding stronger.

Deidre Ebrey, director of Economic Development and Marketing of the city of Moore said, "It is tremendous. I honestly can't believe it, which I don't know why I can't believe it, because I have lived here all my life and we have done this over and over and over again [rebuilt after severe weather]. I'm almost ashamed that this time I thought we couldn't, but again they've proven me wrong. I'm so grateful and glad that I'm wrong."

Ebrey has witnessed the destruction that Moore has overcome from previous tornadoes and said that it was very difficult emotionally for the citizens to recover from the May 20, 2013, tornado. Along with the emotional loss, within the 22-square-mile town, there was a lot of structural damage as well.

The National Weather Service stated that the tornado was on the ground for 17 miles, which is more than half of the entire city of Moore, where an approximated 1,100 homes were destroyed.

RELATED: Moore Tornado Makeup: Nature's Fury Anniversary of Moore Tornado Poses a Painful Reminder for Some Victims Raw Footage of Destructive Moore Tornado

The NWS Norman, Oklahoma, office originally gave the tornado a preliminary rating of EF4 but has since revised that estimate to an EF5, the highest rating on the Enhanced Fujita scale. EF5 tornadoes are strong enough to blow away big houses and collapse tall buildings; winds are estimated at more than 200 mph.

Ebrey attributed immediate success to preparedness and the lead time of tornado warnings. Donna Wickes, director of community planning and development for the U.S. Department of Housing and Urban Development, said long-term success will be due to the careful planning process.

"When you have situations like Moore, Oklahoma, there are three phases that I like to think they [victims] go through. The first 48-hour period of awe and shock, followed by the community implementing interim and short-term fixes and then the planning process for long-term recovery," Wickes said.

The first 24 hours after the tornado, Ebrey recalled images of citizens emerging from their storm shelters and literally picking up the pieces of what was left of their homes in an effort to start the process of rebuilding. She said that the debris removal process is sometimes hard for her to comprehend.

On May 29, 2013, the official large-truck debris removal process began. A total of 173,000 tons of debris was removed from Moore's city limits as well as 12,000 truck loads that were hauled out of the city. Moore was officially cleared of all large debris by Sept. 6, 2013, Ebrey said.

Debris removal, an important part of the rebuilding process, comes at a hefty price, according to Elizabeth Jones, community development director for the city of Moore.

"Looking at past numbers and seeing what we spent on debris removal, we knew it was going to be extremely expensive; $15 million is what the city put in for debris removal," Jones said.

FEMA met the city of Moore's immediate needs, such as search and rescue, basic repairs to the infrastructure, which was all paid for by emergency funds since a presidential disaster was declared.

Once debris was cleared, the progress continued forward. In mid-March, Moore's city council voted unanimously to bolster and upgrade building requirements of residential homes. Old codes were written where homes could withstand only 90 mph.

"This time, we took a stance that we have not done in the past, and that no one has done in the past, and that is to fortify our residential building codes. The hope for that is so that we can see less structural damage. Mind you, these were massive storms that came through, EF4 and EF5 that came through with wind speeds higher than 135 mph, but still, when you look at the homes that were completely destroyed and those that might be a street over, they would have had far less significant damage had they been built to these new standards," Ebrey said.

"Those first four weeks were really about focusing on the long-term picture. Where do you want to be in the future, and based on historical data, we knew this will happen again [tornadoes]. The planning process really impacted all infrastructure and it really changed the footprint of Moore," Wickes said.

New building codes were designed to have significant upgrades such as alterations to residential garage doors. Engineers who were a part of the planning process learned that often the garage door was compromised first, which then led to a lot of structural damage. New doors will be able to withstand 135-mph winds, and this new standard will help keep the integrity of the structure.

While the town is not completely back to normal, the goal is well within reach.

"We are at the point where 1,087 homes that were completely destroyed in our city limits. We have on-file building permits, for 549, meaning over half of those destroyed homes are either built back or in the process of being built back," Ebrey said.

Fewer than 10 homes are still in the condemnation process, and only eight homes have had no activity since the storm.

"When the storm first hit, I took the personal out of it, the heartbreak, and really planned. You have to move forward to make things better. I'm glad there was no rushing during the planning process. The people of Moore were patient when we told them to wait those 103 days before they rebuild and it paid off. Better planning made for better outcomes and they understood that if they waited they would get more. This is a precedent set across America," Wickes said.

The success and planning to restore Moore keeps on growing. Volunteer groups have been showing up by the bus loads over the past year to help with the efforts. Groups that formed on Twitter such as #ServeMoore, students on spring break, athletic teams at both the collegiate and professional level have all chipped in and lent a helping hand to Moore.

"We want to thank everybody and we're struggling with just how to do that, to list every single entity, but we just don't know how to start to do that. It speaks to the heart of America and to where we are, the heartland. We're in a vibrant area here and in a community where everyone wants to be apart of our schools and moving in at a fast pace because we have a great quality of life on our good days. When we have bad days, and May 20th was a really bad day, our expectation is to get back to our full potential as an amazing, thriving suburb."

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Often after severe weather or natural disaster strikes, hundreds to thousands of people are left homeless and hopeless, picking up the pieces. While recovery is typically a lengthy process, one dog and her owner are working side-by-side to provide comfort to disaster victims in the aftermath of a storm.

"That unconditional love of a dog is what really helps people," Canines for Christ Volunteer Ron Leonard said. "It allows people to have comfort."

Leonard and his rescue Labrador Retriever-mix, Molly, have been traveling tens of miles from their home in Nashville, Tennessee, for two years now to visit disaster victims and show them love, hope, kindness and compassion.

"Molly is not a service dog; Molly is a therapy dog," Leonard said. "She's just there for comfort."

As a therapy dog, Molly first went through obedience training then successfully passed therapy training with the Canines Good Citizenship Award. During her training, Molly was taught how to help people by learning how to sense and detect different human emotions, and as a result, she was officially certified as a therapy dog.

Retired United States Army member, Ron Leonard, and his dog, Molly, travel to post-disaster areas to help victims heal emotionally. The duo are volunteers with Canines for Christ. (Photo/Ron Leonard)

Following her schooling, Molly and Leonard journeyed to various disaster sites as well as nursing homes, assisted living facilities, children's hospitals, cancer wards and even some emergency rooms to offer consolation to those suffering.

"Molly comes in and is able to neutralize the situation and be there to just administer a presence," Leonard said.

Currently, Molly and Leonard are in route to Fayetteville, North Carolina, where a severe storm outbreak spawned a tornado that ravaged the town on Tuesday, April 29, 2014, leaving behind a trail of destruction.

Looking at Mayflower, Fayetteville and Tupelo, the three major areas that were hit recently by tornadoes, people impacted go through a grieving process and when they reach the fourth phase in the process, depression, that's where we come in, Leonard said.

RELATED: Is There More Than One Tornado Alley in the US? AccuWeather Severe Weather Center Community Becomes 'Living Laboratory' After Tornado Decimates Town

As Molly and Leonard look to aid victims emotionally post-disaster, the duo always has to be aware of the situation at hand.

"People can be naturally scared of dogs," Leonard said. "We have to be really careful because we never want a person to be more traumatized than they already are.

Besides exercising caution around victims, the pair has to ensure that their visit is welcome as some facilities do not allow animals, even dogs, on the premise.

While not everyone has the skills and economic capabilities to aid disaster victims in the rebuilding process, Leonard believes that he and Molly are able to help in a different and special way.

"Everyone out there really wants to make a difference and their dogs can really make that difference," Leonard said. "Dogs can't talk to them [people], but a dog can feel what they feel."

Have questions, comments, or a story to share? Email Kristen Rodman at Kristen.Rodman@accuweather.com. Follow us @breakingweather, or on Facebook and Google+.

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A new satellite image reveals the damage wrought by an EF4 tornado as it tore through Arkansas on April 27.

The tornado track runs from the upper right to the lower left of the image, traveling through the towns of Mayflower and Vilonia, Arkansas. This image, released yesterday (May 6), was taken on May 2 by NASA's Advanced Land Imager on the Earth-Observing-1 satellite, according to NASA's Earth Observatory.

The storm that spawned this tornado came from a system that moved in from the Rocky Mountains, pushing a cold front with it, according to the National Weather Service office in Little Rock, Arkansas. The interaction of cold air with moist, warm air created the perfect breeding ground for thunderstorms, and the NWS warned that tornadoes and hail were possible. [Video: Deadly Tornado Outbreak Seen from Space]

A tornado is born

One storm northwest of Little Rock turned into a supercell storm. In a supercell, a cold front forces warm, moist air to rise. But as this moist air cools and condenses, it creates a downdraft of cold air. When warm updrafts are balanced by cool downdrafts, the storm can churn along for hours — and form tornadoes.

At around 7 p.m. local time on April 27, the supercell northwest of Little Rock did just that. The resulting twister had winds of between 166 and 200 miles per hour (267 to 322 km/h). The estimated wind speeds and high levels of damage gave the tornado a rating of EF4 on the Enhanced Fujita (EF) tornado scale.

The tornado traveled northeast more than 41 miles (66 km) and remained on the ground for an hour. Hundreds of homes were destroyed, some swept entirely from their foundations. Sixteen people died in the tornado, including an Iraq war veteran who died shielding his 5-year-old daughter from a falling beam when their home was destroyed and 7- and 8-year-old brothers whose parents were seriously injured.

The tornado was the deadliest in Arkansas since 1968, according to the NWS.

Weather damage

The Mayflower-Vilonia tornado was not the only twister spawned by the April 27 storm. Another tornado hit Quapaw, Oklahoma, that evening, killing one person before crossing the state line into Baxter Springs, Kansas. Another tornado hit in Tennessee not far from the Alabama state line.

Floods also affected many areas in Arkansas, Missouri, Alabama and Florida as a result of the storm. As the system moved east, it brought moisture to the mid-Atlantic and Northeast, causing localized flooding in Virginia, Maryland and Delaware.

Follow Stephanie Pappas on Twitter and Google+. Follow us @livescience, Facebook & Google+. Original article on Live Science.

Arkansas Before Tornado

This image, from April 25 and acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite, shows the area before the storm.

Arkansas After Tornado

This image, acquired on April 28 by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite, shows what appears to be a tornado track north of Little Rock, Arkansas. The tracks are pale brown trails where trees and plants have been uprooted, leaving disturbed ground.

Arkansas Tornado

Drone video screenshot of the Arkansas tornado, shot right after it moved just south of Mayflower, Ark.

Arkansas Tornado

Drone video screenshot of the Arkansas tornado, shot right after it moved just south of Mayflower, Ark.

Arkansas Tornado Path

Rotation associated with the parent storm on 04/27/2014 was persistent for roughly 40 miles (Tornado #1) before weakening (where the gap is indicated). Another tornado (Tornado #2) was likely spawned a short time later by the same storm and tracked through White, Jackson, and Independence Counties. Note: Tornado #2 may actually be several tornadoes. This will be determined through damage surveys.

Kansas Tornado

A tornado that formed just north of Fort Scott, Kansas and caused damage as it moved north.

Kansas Tornado

A tornado that formed just north of Fort Scott, Kansas and caused damage as it moved north.

Kansas Tornado

A tornado that formed just north of Fort Scott, Kansas and caused damage as it moved north.

A cold start to 2014 kicked off a quiet tornado season this year, which has seen the fewest twisters since 1915, according to preliminary National Weather Service (NWS) reports.

Notably, no one has died in a tornado so far this year — which represents another record in the modern tornado-tracking era, which started in 1950.

Through April 21, the United States had reported just 20 EF-1 tornadoes, said Harold Brooks, a senior researcher at the National Oceanic and Atmospheric Administration's National Severe Storms Laboratory in Norman, Okla. "My best guess is that this is the slowest start since 1915, and maybe even 1900," he said.

The average number of EF-1 tornados by this point in the year is 157, according to NWS statistics. Tornadoes are ranked on the "Enhanced Fujita" or EF damage scale, with 0 being the weakest and 5 being the strongest. The number of EF-1 tornadoes is a better way to compare each season than the number of EF-0 tornadoes, Brook said. That's because the number of EF-1 twisters has consistently hovered between 500 to 600 yearly for the past 60 years, while the weaker EF-0 tornadoes varied tremendously, from 50 to about 800 per year, he said. [The Top 5 Deadliest Tornado Years in U.S. History]

You can thank the lingering winter for quelling any powerful twisters. "We had three straight months of below-normal temperatures, and that meant fewer than normal tornadoes," Brooks told Live Science. However, a colder-than-normal summer means more tornadoes than normal, Brooks said.

The cold temperatures also meant Oklahoma finally got relief from its string of deadly tornadoes, with a tornado-free streak from Aug. 7, 2013, through April 13, 2014. The Norman, Okla., NWS office set a new record for its longest tornado-warning-free stretch on April 13, at 316 days. The previous streak was 293 days, set in 1991.

There have been no EF-3 or stronger tornadoes in the United States this year.

But don't expect the pattern to continue, Brooks cautioned. "We've got ourselves a pretty reasonable chance of a significant tornado occurrence this weekend, so we could get closer to normal pretty quickly," he said.

Tornado frequency peaks in May, with a little more than half of the country's EF-1 twisters hitting in April, May and June.  Weather patterns shift in spring — warm, moist air moves northward from the Gulf of Mexico and clashes with cold, dry air heading south. The colliding air masses often meet over the Southern Plains in April and the Northern Plains in June, giving rise to the sweeping storms that birth tornadoes.

And both 2012 and 2013 were below-average tornado years, though they both experienced deadly tornadoes. In 2013 — another year with a colder-than-average March in the Southeast — the Moore, Okla., EF-5 tornado killed 25 people and caused $2 billion in damage. In 2012, when drought parched much of the Plains, killer tornadoes ripped through Indiana and Kentucky.

"Just because it's been quiet doesn't mean it's going to stay quiet," Brooks said. "The beginning of the season tells us nothing about the rest of the season."

Email Becky Oskin or follow her @beckyoskin. Follow us @livescience, Facebook & Google+. Original article on Live Science.

Has a tornado warning been issued in your area? 

Are warning sirens going off? 

If so, you may only have moments to get to shelter. Don't panic though, here is everything you need to know about how to survive a tornado.

Additional Information: 

• Red Cross Hotline: 1-866-GET-INFO 
• You can find a shelter using the Red Cross Shelter View App.
• FEMA Tornado Information Site

Each year more than 1,200 tornadoes hit the United States and despite that high number, few things in nature continue to inspire as much wonder and awe as a twister. These events are some of the most violent storms that happen in nature bringing an intense mixture of wind, rain and lighning to those in their paths. Even though much has been learned about tornadoes over the past few decades, there is still quite a bit of unpredictability that comes with these storms as well.

We created this infographic to help you understand a bit more about them. 

An outbreak of severe weather battered parts of the midwestern and southern United States yesterday (Feb. 20) with damaging winds and strong storms, including several tornadoes reported in Illinois and Georgia. The same system is working its way over the East Coast today (Feb. 21), with several tornado warnings and watches issued already.

But it's February, not April, when tornado season usually gears up, so what gives?

While the main tornado season typically stretches from spring to early summer, wintertime twisters are not altogether uncommon, said Greg Carbin, a meteorologist with the National Weather Service's Storm Prediction Center in Norman, Okla.

"Tornadoes can happen at any time of the year, in any month of the year, and in just about any location in the country," Carbin told Live Science.

Yesterday's tornadoes in the Midwest struck during the so-called transition season — the period between winter and spring.

"Typically we see these tornado events in the transition season, and the reason for that is you have the vestiges of both seasons that can bring about the ingredients for strong, violent storms," Carbin explained.

In the winter and early spring, tornadoes are often associated with the jet stream, which is a band of strong winds high above the atmosphere that can influence weather patterns by jostling air masses around.

Tornadoes form in environments of unstable air, usually when warm, moist air is trapped under a layer of colder, dryer air. In Illinois, unseasonably warm, springlike temperatures mixed with cold air to produce stormy conditions, said Illinois state climatologist Jim Angel.

"We had a cold front that moved through the state, and at the head of it, we had warm moisture coming up from the Gulf of Mexico," Angel told Live Science. "The warm, humid conditions and the strong cold front pushing through triggered lines of thunderstorms."

Four possible tornadoes touched down in central Illinois yesterday, causing power outages and minor damage in the region, according to the NWS. Severe storms also ripped through Indiana, Kentucky, Alabama, Mississippi, Tennessee and the Carolinas, and several tornadoes were reported in Georgia.

Today, Angel and his colleagues are conducting surveys in the aftermath of the storms, but so far no casualties have been reported. Once the scientists parse the data, Angel will also be able to say precisely how many twisters touched down in the state.

Still, tornadoes in February are not necessarily harbingers of the main tornado season to come.

"There's no real connection that we've been able to find," Carbin said. "And, up until yesterday, we were running at a record low number of tornadoes for the year."

Follow Denise Chow on Twitter @denisechow. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

Natural disasters can create conditions that put survivors at risk for fungal infections, which are often overlooked, according to a new report from the Centers for Disease Control and Prevention.

Earthquakes, hurricanes, tornadoes and other natural disasters can displace harmful fungi from their natural habitat, potentially bringing them into contact with injured and vulnerable people, the report said. Individuals may inhale fungal spores, or the spores can find their way into wounds, resulting in infections.

For example, after the devastating 2011 tornado in Joplin, Mo., 13 severely injured people developed a rare fungal infection called mucormycosis. The type of fungus that causes this infection is found in the soil and decaying organic matter that victims were exposed to as a result of the disaster. [Top 10 Deadliest Natural Disasters in History]

Following a 1994 earthquake near Los Angeles, more than 200 people developed a fungal infection called coccidioidomycosis, also known as Valley Fever. Landslides and aftershocks caused by the earthquake generated dust clouds, which dispersed soil fungus that people inhaled, the report said.

Although not a very frequent occurrence, fungal infections following disasters may become more common with climate change, the report said. Warmer temperatures may allow harmful fungi to expand into new areas. Coupled with the predicted increase in extreme weather, "a larger or more geographically widespread ecologic burden of pathogenic fungi could lead to greater numbers of disaster-associated fungal infections," the report said.

Health care providers should be aware of the potential for people to develop fungal infections after natural disasters, so that treatment can be started early, the report said. Fungal infections are sometimes mistaken for other illnesses, such as bacterial infections, which can delay appropriate treatment. After the Los Angeles earthquake, for example, 93 percent of Valley Fever sufferers received one or more antibiotics before their fungal infection was diagnosed, the report said.

Typically, these fungal infections are uncommon in people with healthy immune systems, so doctors may not think to look for them. So when patients have infections that are not responding to antibacterial treatments, doctors should consider fungal infections, the report said.

The delay in getting medical treatments that often happens after natural disasters can also contribute to these infections taking hold, the report said.

"Strategies to reduce disaster-associated fungal infections should be considered within the broader context of comprehensive and sustainable risk-reduction methods to prevent disaster-related injury and illness," the researchers wrote in their report, published in the March issue of the CDC journal Emerging Infectious Diseases.

Follow Rachael Rettner @RachaelRettner. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

SAN FRANCISCO — The trail of twisted metal and torn roofs left behind by massive twisters is growing longer and wider, a sign that tornadoes may be growing stronger, climate scientist James Elsner said here Tuesday (Dec. 10) at the annual meeting of the American Geophysical Union.

Beginning in 2000, tornado intensity — as measured by a twister's damage path — started rising sharply, said Elsner, of Florida State University. "I'm not saying this is climate change, but I do think there is a climate effect," he said. "I do think you can connect the dots."

Devastating tornado outbreaks in recent years, such as the massive storm that injured hundreds in Moore, Okla., this summer, have focused attention on whether climate change is altering tornado frequency and strength. Just last week, a heated debate played out in an op-ed on LiveScience and the New York Times over whether tornado-tracking data could answer these questions. One scientist claimed the data show twister numbers are dropping, but tornado experts said changes over time in how weather officials assess tornado size and damage make it difficult to look for climate patterns. [Gallery: Moore Tornado Damage]

But  Elsner said tornado data are good enough to reveal whether global warming is altering twisters. "I've been working with hurricane tracking data for 25 years, and tornado tracking data is better," Elsner said. "We have the tools, we have the data to answer the question. Statisticians drool when they see stuff like this."

"I think we're at the point where we were 30 years ago with hurricanes. People were skeptical about the connection between hurricane and climate, but now they don't even blink," he said.

Elsner is the first to admit he doesn't have the climate answers, but he said his early results are a step in the right direction: finding a way to solve the data conundrum.

Elsner's solution was to drop the human factor. Instead, he looked at wind speed and the size of the damage path (its length and width) to gauge whether tornado intensity has changed since 1994. (The United States has been almost completely covered by Doppler weather radar since 1994.) Using the damage path to gauge intensity avoids problems such as analyzing tornado strength via the Fujita and Enhanced Fujita scales, which are based on observations by weather service officials, he said.

Elsner analyzed damage paths and wind speeds using a statistical model. The result: a sharp upward spike starting in 2000. He also looked at earlier data, since the 1970s, which showed a much slower rise.

Puzzling out how climate change alters tornados is the big next step, Elsner said. One way this could happen is by adding moisture (via humidity) to fuel storms in Tornado Alley, the storm belt where tornadoes spin up in the United States. Warmer air holds more moisture. But Elsner said it was also important to track tornadoes in Canada, because there are hints that big ridges and troughs in the jet stream's powerful winds could be triggering more tornadoes up north, and fewer in the United States.

"We really need a North American data set to answer questions about frequency," he said.

Email Becky Oskin or follow her @beckyoskin. Follow us @livescience, Facebook & Google+. Original article on LiveScience.

This open letter was written by six, leading tornado experts from research institutions across the United States. Their brief bios follow below. The authors contributed this article to LiveScience's Expert Voices: Op-Ed & Insights.

Twisters returned to the national spotlight after a Nov. 17 outbreak viciously tore through 12 states, leaving eight people dead.

Research data show that climate change caused by human behavior is fueling more frequent and intense weather, such as extreme precipitation and heat waves — so it's only natural to wonder if this applies to tornadoes, too. Scientists need more data and time to fully address that connection.

That said, some high-profile scientists are misleading the American public about what is, and is not, known about global warming and tornadoes.   [Something Is Rotten at the New York Times (Op-Ed)]

For instance, University of California, Berkeley, professor Richard Muller argued in a recent New York Times opinion piece that "the scientific evidence shows that strong to violent tornadoes have actually been decreasing for the past 58 years, and it is possible that the explanation lies with global warming."

The honest "truth" is that no one knows what effect global warming is having on tornado intensity. Tornado records are not accurate enough to tell whether tornado intensity has changed over time.

Although it is a bit of an exaggeration to say, "backyard dust devils are reported," Muller notes — correctly— that climate change is not responsible for the dramatic rise in annual tornadoes since 1950. Rather, the larger numbers come from improved detection and reporting of weak tornadoes, particularly EF0 tornadoes, where "EF" refers to the enhanced-Fujita scale used by the National Weather Service (NWS).  

However, Muller then uses the record of severe tornadoes — those rated EF3 to EF5 and responsible for the most extreme damage and casualties — to reach the following conclusion: "One thing is clear … The number of severe tornadoes has gone down. That is not a scientific hypothesis, but a scientific conclusion based on observation. Regardless of the limitations of climate theory, we can take some comfort in that fact."

His confident claim is based on raw U.S. National Oceanic and Atmospheric Administration (NOAA) records showing an apparent decline in EF3 to EF5 tornado reports in the past 58 years. Unfortunately, it illustrates a lack of understanding of how those reports have been developed, and the changes in the process over time. Scientific conclusions must be based on reliable observations, not just any observations.

Ironically, the reason Muller says one shouldn't attribute the increase in weak (and therefore total) tornado reports to climate change is likely the same reason the intensity of tornadoes has appeared to decline: reporting has not been consistent over the period the tornado records span.

The meteorological community knows very well that early official records systematically rated tornadoes stronger than those in the 1980s and 1990s — that is, tornadoes were awarded higher EF-ratings in those decades than they would have received in more recent times.

Tornadoes occurring prior to the mid-1970s — when the NWS adopted the enhanced Fujita scale — received ratings retrospectively by meteorology students who relied on qualitative damage descriptions in newspaper archives. This effectively "inflated the grades" of those tornadoes because the later ratings came only after considerable in-person scrutiny of the damage, often by engineers who considered not just the damage but also the quality of the construction of damaged structures. The evidence for the overrating of earlier tornadoes includes the fact that environments and damage paths of many strong tornadoes in that retrospective era shared characteristics with weaker tornadoes from later years.

Considerable evidence uncovered in the last decade suggests that previous tornadoes actually were underrated compared to the 1980s and 1990s.

One factor contributing to those ratings was a 2003 policy that required a special team of experts to evaluate the damage of the strongest tornadoes. In an unforeseen consequence, local NWS offices had a tendency to assign lower initial ratings, eliminating the expense and complexity of involving external evaluators. In addition, concerns about construction practices from the engineering community placed additional emphasis on poor construction by damage assessors from the NWS, leading to lower ratings.

Also, in another complication in assessing long-term tornado intensity trends, the "damage indicators" used to rate tornadoes recently have changed with the adoption of the EF scale, making it dubious to compare tornadoes of the past with those of the present.

Recently, truck-borne Doppler radar observations of tornadoes identified a number of cases in which the radar-measured winds are considerably faster than the official NWS rating implies. For example, the winds measured by these radars in last May's 2.6-mile-wide tornado near El Reno, Okla., topped 280 mph, which would have placed it well into the EF5 range (200+ mph). The official NWS rating based on the available damage indicators, however, was EF3 (136–165 mph).

Finally, Muller's simple analysis of tornado reports does not address possible changes in the seasonality and/or regional nature of tornado occurrence. In fact, the latest climate-model experiments agree that further global warming is likely to increase the likelihood of conditions favorable to the severe thunderstorms that produce tornadoes in the spring and autumn. Although these climate models do not resolve tornadoes, they do predict an increase in the ingredients responsible for past tornadoes.

Paul Markowski, professor of meteorology at Penn State University, was a leader of the recent Second Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX2) and 2013 recipient of the National Weather Association's Fujita Award for his research on tornado formation.

Harold Brooks is a senior research scientist at NOAA's National Severe Storms Laboratory, has authored numerous scientific papers on tornado climatology, and was a contributing author on the recent Intergovernmental Panel on Climate Change's Fifth Assessment Report.

Yvette Richardson, associate professor of meteorology at Penn State University, is a Councilor of the American Meteorological Society and was a leader of the recent Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX2).

Robert J. Trapp, professor of atmospheric science at Purdue University, has published several articles on the topic of severe thunderstorms and climate change.

John Allen, postdoctoral research scientist at the International Research Institute for Climate and Society at Columbia University, has authored several recent journal articles on relationships between the climate system and severe thunderstorms.

Noah Diffenbaugh is an associate professor in the School of Earth Sciences and the Woods Institute for the Environment at Stanford University. He is currently a Lead Author for the Intergovernmental Panel on Climate Change.

The views expressed are those of the author sand do not necessarily reflect the views of the publisher. This article was originally published on LiveScience.

This article was provided by AccuWeather.com.

While much of the United States will be calm for Thanksgiving Day, there are some trouble spots, including rain in California and lake-effect snow downwind of the Great Lakes. Mother Nature was not so kind for some Thanksgiving holidays in our country's history.

Below is a list of a few of the nation's most memorable Thanksgiving weather events in chronologic order:

1. The Snow Bowl

Two days after Thanksgiving on Nov. 25, 1950, the Ohio State Buckeyes hosted the Michigan Wolverines in Columbus, Ohio, for a collegiate football game that would go down in history.

Now referred to by some as the "Blizzard Bowl," the game is famous for its blizzardlike conditions, as temperatures dropped 10 degrees during the game, accompanied by blowing snow and wind.

During the game, the air temperature was between 10 F and 16 F with a wind chill between -8 F and -1 F. During the middle of the game, the visibility was down to one quarter of a mile and sustained winds rose to 22 mph.

Michigan was victorious without ever even earning a first down. Both teams punted more than 20 times with the entirety of the game's points coming from blocked kicks. The final score of the game was 9-3.

2. Hurricane Iwa

While hurricanes in the Hawaiian Islands are somewhat rare, the Hawaiian Island of Kauai was slammed by Hurricane Iwa just two days before Thanksgiving on Nov. 23, 1982. This hurricane was the first direct hit on the island since 1959.

As the storm made landfall, sustained winds were 86 mph with wind gusts up to 105 mph. The peak storm surge, between 6 and 8 feet, crashed on the southern shores of Kauai and caused major damage, later costing the island more than $150 million.

Another $50 million was shelled out after the storm for damages on the island of Oahu. Despite the hefty costs for damages, there were no deaths on land.

3. San Joaquin Valley Dust Storm

Just one day after Thanksgiving in 1991, a blinding dust storm swept through California's main highway, the Interstate 5, in San Joaquin Valley area. As one of the main travel days around the holiday, this dust storm proved to be catastrophic as it caused a 100-vehicle chain accident on the freeway. More than 15 people lost their lives and more than 130 were injured as a result of the massive pileup.

According to The Los Angeles Times, the California Highway Patrol ended up closing a 150-mile stretch of the roadway due to the storm. The portions of the closed highway included the high traffic areas near Bakersfield to Los Banos.

4. 1992 Tornado Outbreak

The weekend before Thanksgiving, a three-day severe weather outbreak unleashed tornadoes, large hail and damaging winds across 13 states.

Spanning from Nov. 21 through Nov. 23, 1992, more than 90 tornadoes spun through states from southeastern Texas to the central portion of the Atlantic Seaboard. Mississippi was hit the hardest during this outbreak, as 21 counties were declared disaster areas after the storms rolled through.

When the outbreak ended, more than 640 people had been injured and more than 25 people lost their lives. This outbreak set the record for the number of tornadoes in the month of November.

5. The Sleet Bowl

While this Nov. 25, 1993 Thanksgiving Day game went down in the history books for Leon Lett's fumble that cost the Dallas Cowboys the victory against the Miami Dolphins, the game also came with some unexpected weather, making it the first time ever that winter precipitation was recorded on Thanksgiving in Dallas.

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A local cold front with strong winds and black and blue skies, also called a Blue Norther, brought cold temperatures and sleet to the Texas Stadium in Irving, Texas, on game day.

Sleet covered the field that day making it hard for players to keep their balance during the game, resulting in a low-scoring game and the blunder that gave the Dolphins a win.

6. Winds in Western Washington

Two days after the 1998 Thanksgiving holiday, dozens of flights were canceled out of the Seattle-Tacoma International Airport after portions of the building lost power due to high winds. Sustained winds of 50 mph swept through much of the western Washington area, downing trees and power lines on the way.

Wind gusts up to 76 mph were recorded in Bellingham, one of the state's largest cities. After the wind subsided more than 250,000 homes and businesses were without power, including all of the 26,000 customers on Whidbey Island, one of the nine islands in Island County, Wash.

Additionally, the state's floating bridge, the Hood Canal Bridge, that connects two of Washington's peninsulas was closed for hours, hindering travel for many headed home.

7. Major Lake-Effect Snowstorm

After a cold front swung across the snow-belt regions on Thanksgiving morning in 2005, winds shifted and ignited lake-effect snow as the bands headed southwestward.

Snow fell all night accompanied by gusty winds 30 mph or more, dumping more than 20 inches of snow in areas off lakes Erie and Ontario. The towns of Ellicottville, N.Y., and West Leyden, Ill., were slammed with 24 inches of snow.

After the storm swung northward, downstate New York was blanketed with 7 inches of snow in the Buffalo metro area.

Have questions, comments, or a story to share? Email Kristen Rodman at Kristen.Rodman@accuweather.com, follow her on Twitter on Google+. Follow us @breakingweather, or on Facebook and Google+.

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Updated at 2:50 p.m. ET.

(ISNS) -- Scientists at the University of Arkansas -- a state where tornadoes are a serious matter -- believe that in at least some circumstances, tornadoes cause less damage going uphill and regain their destructive power going downhill.

The implication is that lower elevations may be safer than higher ground, and buildings can be constructed accordingly.

The study, presented at the American Conference on Wind Engineering in June, provoked an immediate and public controversy.

The research by R. Panneer Selvam, a professor of civil engineering, and his graduate student, Nawfal Ahmed, in Fayetteville, was based on aerial photos taken after two major tornadoes that struck different cities in 2011. 

They used National Oceanic and Atmospheric images at Tuscaloosa, Ala., a day after an April 28 tornado, and 16 days after the May 22, Joplin, Mo., incident, and overlaid them over Google Earth photos to show before-and-after images.

The Joplin tornado was rated at EF5 on the Enhanced Fujita Scale, the highest realistic measurement of destructiveness with winds of more than 200 mph. One-hundred fifty-eight people died in the incident, and damage was estimated at $2.8 billion, the costliest tornado in American history.

The Tuscaloosa event was an EF4, with winds of 190 mph. Sixty-four died in that tornado, and damage was estimated at $2.2 billion. 

Upon studying the images, the researchers reported that “a hill can act as a protection wall for buildings located on the leeward part of the hill.”

They reported that the photos showed less damage on hill slopes, both the windward and leeward sides; that tornadoes seem to favor higher elevations and move in that direction when they can, and, most controversially, in areas with hills and valleys, tornadoes will skip over the valleys and concentrate the damage on the hills.

That would be good to know if true, because “every place in the world that has flat land has tornadoes,” Selvam said.

The study, reported in a press release from the university (the study has not been peer-reviewed or published), provoked an instant backlash, including a televised debate between Selvam and a local television weatherman.

“I don’t want people to think they are somehow safer in a valley and not take the proper precautions,” said Dan Skoff, of KNWA and FOX 24, both television stations in northwestern Arkansas. Skoff, who also is a storm chaser, has a degree in meteorology from the University of Oklahoma in Norman.

In the debate, Skoff pointed out that Selvam studied only two tornadoes and it is irresponsible to make general statements based on so few examples. Further, there are other examples of tornadoes that had different damage patterns.

In one anecdote, Skoff described the death of a 50-year-old woman who died when she, according to neighbors, did not take the proper precautions or take shelter, thinking she was safer in a lowland home. There were multiple examples of tornadoes that were damaging at all elevations.

Skoff said it is a common misconception that people think they are protected from tornadoes in valleys. He was particularly upset by the notion that the tornadoes skip around hills.

“This is exactly what we don’t need in this area is for people to get complacent, to think that tornadoes can’t get down into ravines and valleys," he said.

Paul Markowski, a professor of meteorology at Penn State, agreed with Skoff.

“I have no doubt that terrain and land surface characteristics affect tornadoes (it's virtually a truism that it does), but I'm extremely skeptical of an ability to generalize terrain's effects, and I think we're nowhere close to being in a position to suggest new building practices as a result of what we've learned from a couple of tornadoes.”

He said there were too many factors that affect the path of destruction, besides elevation. For example, slope, intensity and motion of the storm, whether there are trees on the slope or corn. 

“I don't think we're close to knowing the answers to any of these questions at this point, though it's an interesting idea that we might someday be able to engineer landscapes to mitigate tornado damage to valuable assets,” he said. 

Selvam admitted that two tornadoes were not sufficient to draw widely applicable conclusions but he could not get funding for further study. He said his findings were general and did not get into the specifics or the geography of the hills. He traced only the damage in these two tornadoes and that is what he found.

“You cannot make the general statement, you are surrounded by hills, you are fine,” he said. “No. Valleys are a complicated issue.”

Editor's Note: An earlier draft of this story misstated that tornadoes may cause less damage while traveling uphill. The University of Arkansas study found that tornadoes could cause more damage traveling uphill, not less.

Inside Science News Service is supported by the American Institute of Physics. Joel Shurkin is a freelance writer based in Baltimore. He is the author of nine books on science and the history of science, and has taught science journalism at Stanford University, UC Santa Cruz and the University of Alaska Fairbanks.

This article was provided by AccuWeather.com.

During January of 2011, Boston was blanketed in 38.3 inches of snow which is about three times the average snowfall amount for the month. As residents began the arduous task of shoveling their walkways, the fire hydrants adjacent to them remain untouched. Buried under mountains of snow, they would be of little use to firefighters who wouldn't even be able to determine their location if needed. These are the types of problems that face the U.S. government every day and can be solved by forward-thinking and innovation. The organization Code For America aims to solve these problems.

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Code For America is a non-profit organization that offers year-long fellowships to talented programmers and visionaries, mostly born into Generation Y, to provide services to overhaul the outdated and overburdened local governments. These systems become even more exacerbated in the face of a natural disaster. However, the perception of bureaucracy is regarded as villainous amongst young adults - an essential concept met with derision and cynicism instead of determination. Nicknamed not-so-affectionately as "Generation Me," the current young adults have been described as being more narcissistic and cynical than any other generation. It is widely believed that "Generation Me" doesn't exhibit the same civic-mindedness that earlier generations had, developed largely around the relevant civil rights issues.

Varying reasons can be attributed to this shift in mindset, but the integral difference seems to be the amazing technologies that have emerged since the creation of the Internet. Generation Me, or more widely known as "Generation Y," were raised in a world where they were seemingly both emboldened and burdened by technology.

Code For America hopes to showcase the exceptions to the rule by utilizing the talents and technologies of Gen Y to create a better government and, as a result, a better society. By applying the technological advancements that are embraced in the private sector, Code For America has provided Generation Y with a place to focus the altruistic spirit it's often been accused of lacking. Code For America Founder Jennifer Pahlka even joked during her 2012 TED talk that the program was the equivalent of the "Peace Corp for geeks."

Pahlka also commented that government was supposed to be "everything [tech people] are supposed to hate." But the program utilizes the technologies that Gen Y has grown addicted to in programs to revolutionize civic efforts. Notable efforts for natural disasters initiatives are Adopt-A-Hydrant, originally created for the city of Boston, and Recovers, a platform most recently being used in Moore, Okla., after the tornadoes in the spring of 2013.

In response to the fire hydrant issue in Boston, Code For America fellow Erik Michaels-Ober created the Adopt-A-Hydrant app. When downloaded or by accessing the site online, citizens can "adopt" a nearby fire hydrant and pledge responsibility for making it accessible to firefighters during snowstorms. By integrating game dynamics, such as being able to name your hydrant and the ability for users to "steal" ownership if it is not done in a timely manner, the app went viral. Pahlka says the program is "showing what's possible with technology today." In stark contrast to traditional government work, the coding for the app was created in a single weekend.

Not only did the app go viral in Boston, it also attracted the attention of other government officials and was re-purposed for other crucial problems with simple modifications. Forest Frizzell, the deputy IT director for the city and county of Honolulu, took note and approached Code For America to use the framework in Hawaii. Hawaii's fire hydrants are not in danger of being buried by snow, but their tsunami sirens are often disabled by thieves stealing the batteries. Without the batteries, the sirens would be rendered useless and citizens left vulnerable to incoming tsunamis without warning. Frizzell told NPR the resulting app, Adopt-A-Siren, was an enormous success with an adoption rate of 75 percent.

More recently, Code For America created a program called Recovers, which aims to help prepare community for disasters and coordinate relief efforts after. Recovers promises "simple tools and set-up" to provide communities with a platform to make actionable decisions after a natural disaster.

The program has been adopted by Moore, Okla., in May of 2013 in response to the EF-5 tornadoes that decimated large parts of the town. The information hub streamlines the traditional and outdated volunteer process by allowing citizens to browse assignments, sign up, offer certain skills, complete liability waivers and ultimately maximize outreach efforts. The site also provides an information center for people to access local news about the recovery efforts to visualize tangible results. Recovers aims to harness the power of the Internet by centralizing relief information and maximizing manpower and donations to help victims of natural disasters.

This service is available to any municipality that signs up and pays a nominal fee to the organization. Recovers recommends utilizing the program before any natural disasters occur - their site explains it "empowers communities to prepare."

So while Generation Y may have already been written off as self-absorbed and cynical, Pahlka believes that the age group has the power to truly be agents for a more effective society. She explained, "It's not just Code For America fellows, there are hundreds of people over the country that are standing and writing civic apps every day in their own communities. They haven't given up on government."

Code For America hopes to bring the power of the people to the 21st century by streamlining and advancing important government projects. By adapting new technologies, the future of these initiatives are limitless. With widespread adoption, Recovers could fundamentally change the way we respond to natural disasters like tornadoes and hurricanes. With Adopt-A-Hydrant, fires could be fought more effectively all around the country. Powered by "Generation Me," Code For America can help solve everyday problems and make natural disaster response much more efficient.

© AccuWeather.com. All rights reserved. More from AccuWeather.com.

The only sure thing about weather forecasts is that they’re wildly different all over the planet. Test your knowledge on the wild ranges in temperature, precipitation and more.

Extreme Weather Facts: Quiz Yourself