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Tropical Weather Could Delay NASA's Last Shuttle Launch

NASA's final space shuttle crew took part in a press conference on June 22, 2011 while standing behind their spacecraft, Atlantis, and Kennedy Space Center's Launch Pad 39A. From left to right: STS-135 mission specialists Rex Walheim, Sandra Magnus, pilot Doug Hurley and commander Chris Ferguson. CREDIT: Z. Pearlman

As space shuttle Atlantis nears its upcoming Friday (July 8) liftoff the last-ever shuttle launch NASA forecasters are keeping a close eye on a tropical wave that is expected to bring winds, rain and even thunderstorms to Kennedy Space Center (KSC) in Cape Canaveral, Fla.

"It is not looking favorable right now for launch," said Kathy Winters, NASA's shuttle launch weather officer, at a press briefing this morning.

The launch would be the last-ever mission of the space agency's 30-year space plane program. Earlier today, NASA officials unanimously voted to clear Atlantis for launch. The shuttle's fueling is expected to proceed, with a 20 percent chance of weather preventing tanking, Winters said.

The liftoff forecast is not as rosy.

"We are concerned about weather for launch," Winters said. "We do have a 70 percent chance of KSC weather prohibiting launch."

Troublemaking wave

A veritable tropical wave of weather threatens to pelt the area around Atlantis' launch pad with thunderstorms and rain, Winters said. Tropical waves, or easterly waves, are long areas of low pressure, oriented north to south, but which move east to west. The current wave is making its way from the Bahamas to Florida over the next few days.

The wave is forecast to bring a lot of moisture and cloud cover, but shouldn't develop into anything more intense, like a hurricane.

The chief concern for launch is the risk of lightning , clouds and rain in Atlantis' flight path, as well as storms at a nearby landing strip, which would be needed in the remote chance the shuttle had to make an emergency landing shortly after launch. NASA launch rules require no stormy weather within 20 miles (32 km) of the shuttle runway.

To make sure lightning is not a threat during launch, NASA has an entire team of meteorologists watching the weather, which helps take some of the stress off forecasters.

"I wouldn't call it pressure," Winters said. "I'd call it exciting."

That hasn't kept other NASA team members from chiding Winters about the cloudy skies in the forecast for NASA's final shuttle launch. NASA's second-to-last shuttle to launch was Endeavour, which disappeared into a cloud layer seconds after liftoff.

"I hope it's not like the last launch, where we only saw it for 22 seconds ... Kathy," Mike Leinbach, shuttle launch director, joked during the briefing.

Weather mulligan

NASA does have a backup plan for the likely chance that liftoff is delayed.

If NASA is unable to launch Atlantis Friday, the space agency has two other chances on Saturday and Sunday (July 9 and 10). After that, NASA would have to stand down to avoid a space traffic conflict with another rocket set to launch an Air Force navigation satellite on July 14 from the nearby Cape Canaveral Air Force Station.

"Friday is game day for us," Leinbachsaid. "We don't want to wait until Saturday. We want to play the game Friday."

Unless the forecast improves, they may be forced to wait. The latest forecast predicts a 60 percent chance of foul weather on Saturday, but conditions improve on Sunday, which is expected to pose only a 40 percent risk of bad weather, Winters said.

"We still have a lot of moisture in the atmosphere over the next three days," Winters said. "It's not clean and green, but it does seem to be improving."

Brett Israel was a staff writer for Live Science with a focus on environmental issues. He holds a bachelor’s degree in biochemistry and molecular biology from The University of Georgia, a master’s degree in journalism from New York University, and has studied doctorate-level biochemistry at Emory University.