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At hurricane season's midpoint, forecasters perplexed

A satellite image shows Hurricane Irene on Aug. 25, 2011, in the Caribbean Sea.

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A satellite image shows Hurricane Irene on Aug. 25, 2011, in the Caribbean Sea.

Remember those predictions of an extremely active hurricane season?

Water temperatures were high. There would be no El Niño to thwart hurricane development. All signs pointed to an ominous season.

Yet on Sept. 1, for only the sixth time since 1950, not a single hurricane had formed in the Atlantic Ocean, Caribbean Sea or Gulf of Mexico.

"If things continue as they have, this could wind up being one of the biggest forecast busts ever,'' said Phil Klotzbach, hurricane scientist with Colorado State University. "Mother Nature throws you some curveballs."

Hurricane forecasters on average predicted about 17 storms this year, with about half becoming hurricanes.

So far, there have been seven tropical storms, including one that formed Wednesday.

"We've had this really quiet year. I'm scratching my head," said Jeff Masters, director of meteorology at Weather Underground. "It should not have been this quiet based on everything we know about tropical Atlantic hurricane seasons."

Part of the reason is dry air.

Hurricanes are powered by warm water, usually 79 degrees or above. Dry air entering a storm can destabilize it or break up a developing system.

That's what happened this summer as a massive cloud of dry air moved off the African coast and into the traditional hurricane breeding ground in the Atlantic and Caribbean.

But dry air has not been the only culprit.

"We have had a lot of vertical shear over the Caribbean Sea,'' Klotzbach said. The reasons are not clear.

"We don't have 100 percent confident explanations for why the season has behaved the way it has,'' said Klotzbach, who issues an annual forecast along with noted hurricane forecaster William Gray.

It has been much quieter than anyone predicted.

Accumulated cyclone energy, one of scientists' key measures of tropical energy in the Atlantic, Caribbean and gulf, is currently at a rating of 9, less than one-fourth of what it would be in an average year.

And it's a similar pattern elsewhere.

"We've had much less activity around the globe,'' Klotzbach said. "It's been one of the quietest years ever for hurricanes.''

But hurricane season runs until Nov. 30 and, as experts are quick to point out, it only takes one to make a bad season.

Forecasters now are keeping watch on Tropical Storm Gabrielle, which formed Wednesday in the eastern Caribbean, the seventh tropical storm of the season. Computer tracking models, however, take the system to the north or even northeast, away from the United States.

Masters said it's looking more like the season's predictions will go bust.

"It doesn't look like anything's going to change, certainly into mid September," Masters said.

Claire Wiseman can be reached at cwiseman@tampabay.com. Follow her on Twitter @clairelwiseman. Pat Farnan can be reached at pfarnan@tampabay.com.

At hurricane season's midpoint, forecasters perplexed 09/04/13 [Last modified: Thursday, September 5, 2013 11:18am]

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