Hurricane Predictions: Can You Trust Them?

The 2006 Atlantic hurricane season opens today, and the early expert forecasts call for above average activity.

Yet, last year, about twice as many Atlantic hurricanes (15) occurred as were forecast. Hurricane Katrina  was the fourth most intense Atlantic hurricane in recorded history.

After the tragic, record-setting, forecast-stomping 2005 season, should we believe the early outlook for this year?

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Yes, says Gerry Bell, lead scientist for NOAA's seasonal hurricane forecast.

The predictions

NOAA forecasts 13 to 16 named tropical storms and eight to 10 hurricanes this year in the Atlantic Basin, which includes the Gulf of Mexico and the Caribbean. (Another top hurricane forecast team, Philip Klotzbach and William Gray at Colorado State University, forecasts similar figures—17 named storms, nine of which will blow hard enough to be called hurricanes).

"NOAA's outlooks always reflect the most confident estimates we can make given the climate signals at hand," Bell told LiveScience. "These are highly confident outlooks and should be regarded as such. However, some weather patterns, which can influence the season as we saw last year, are simply not predictable this far in advance."

While scientists debate the possible impact of global warming  on hurricanes, the underestimate of what 2005 had in store resulted from four factors, two of which are unknown every year at this time, Bell said. A third factor, a combo plate of overall wind measures, air pressure and sea surface temperature patterns, is the same this year as it was last. And the fourth factor, current sea surface temperatures, are about a half degree Fahrenheit cooler than they were at this time last year, Bell said.

For that reason, he anticipates this season will be less devastating than last. 

Against the odds

The May 2005 NOAA forecast was off because El Nino conditions that can develop in August–October 2005 and tamp down Atlantic hurricane activity but did not materialize. NOAA knew this might happen and made a best guess based on the odds. This time, the odds misled them.

Also, it's easier to forecast storm activity once the season has started. It's harder to predict early activity between June and July. And things took off early last season during those months when a record-setting seven named storms struck.    "This is one reason NOAA updates the outlook in August. NOAA's August 2005 outlook indeed called for a near-record season," Bell explained. Klotzbach and Gray also update their forecast as the season progresses.

Some interesting numbers from last year:

• Last season, with 15 Atlantic hurricanes, really was unusual. Between 1995 and 2005, the Atlantic hurricane season averaged eight hurricanes.
• The 2005 hurricane season is the most active season on record, although 1950 still holds the record for the most major hurricanes (Category 3 or higher).
• The 2005 hurricane season set the record for the most Category 5 hurricanes in a single season—four.
• 2005 holds the record for the most storms ever to form in the month of July—five.
• Katrina was the most costly hurricane on record in the United States., at a current estimate of $80 billion.

In the end, the numbers matter little at a human level. One hurricane landfall can mean disaster for a region, and the NOAA forecast for the 2006 season calls for two to four hurricanes to come ashore in the United States.

"We urge people to begin preparations now," Bell said, "before the hurricanes begin, so that they will be prepared. Those that prepare fare much better than those that do not."

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