HOUSTON — The skies, it turned out, did not fall.

Most tropical storm experts had predicted that this year’s Atlantic hurricane season would be deadly. Instead, with just a few days remaining in the June-November hurricane prime time, 2006 has turned out to be a dud. Not that anyone living along the Atlantic and Gulf coasts is complaining about the errant forecast, after a vicious 2005 hurricane season that spawned Katrina, Rita and other killer storms. But inside the small, elite fraternity of hurricane forecasters, there is soul-searching over how they got things so wrong – and concern that their Chicken Little mistake could add to public complacency when next year’s hurricane season gets under way.

Back in May, experts at the National Oceanic and Atmospheric Administration predicted there would be 13 to 16 named tropical storms this year, eight to 10 of which would become hurricanes and four to six of which would be “major,” or Category 3, 4 or 5.

Meanwhile, a second group of hurricane experts at Colorado State University predicted 17 named storms, nine of which would become hurricanes and five of which would be major.

In fact, this year there have been just nine named storms, only five of which became hurricanes and only two of which were intense – and none of them hit the U.S. mainland as hurricanes. And there’s nothing more on the horizon between now and Nov. 30, when the 2006 hurricane season will formally close.

That means the hurricane experts, who pride themselves on their sophisticated computer models and state-of-the-art forecasting tools, were less accurate than even the average TV weather forecaster on the 10 p.m. news.

“It does make us a little more humble in trying to figure out what’s going to happen in the future,” said Chris Landsea, a member of the federal hurricane forecast team. “I think it’s kind of a notice to us that we don’t know as much as we thought we did.”

The biggest mistake forecasters made this year was failing to predict the onset of an El Nino weather pattern during the summer. El Nino, a periodic warm-water trend in the Pacific Ocean, almost always suppresses hurricane activity in the Atlantic by creating more crosswinds in the upper atmosphere that tear tropical storms apart before they can become hurricanes.

Experts said other factors impeded the formation of hurricanes as well, including large dust storms off of West Africa and a strong sinking of warm air over the Caribbean, which inhibited the formation of thunderstorms that could have evolved into tropical storms. Steering currents over the Atlantic pushed storms northward and back out to sea before they could threaten the U.S.

All those unforeseen factors sent hurricane forecasters back to refine their computer models in the hope that they won’t be caught off-guard next year.

“Obviously we’re not thrilled that our forecast turned out wrong, but you try to learn from what happened,” said Phil Klotzbach, the lead forecaster at the Colorado State University Tropical Meteorology Project. “It’s like, hey, there were 18 ESPN baseball experts and none of them picked the Tigers or the Cardinals in the World Series this year. It’s just the nature of the business.”

The experts warn, however, that this year’s unexpectedly mild hurricane season does not alter a larger reality: The Atlantic and Gulf coasts are less than midway through a recurring 30-year cycle of stronger, more frequent tropical storms. That means that the record 2005 hurricane season, with 27 named storms, 15 of which became hurricanes and seven of which were intense, was much closer to the new norm than this year.

“This year, people were saying, “Oh, that hurricane cycle you’ve been talking about is over now, right?”‘ said Stephen Leatherman, director of the International Hurricane Research Center at Florida International University in Miami. “And I say, “Wait a minute, no, we’ve got another 20 years to go.”‘

The veteran hurricane forecasters have had off years before. Since 1999, the federal forecast team has gotten five out of eight of their May preseason forecasts correct. They did slightly better with their August forecasts, issued midway through the hurricane season, nailing seven out of nine.

But a new team of hurricane forecasters, at North Carolina State University, got this year’s forecast largely right.

Focusing their predictions only on the Atlantic Ocean off the U.S. East Coast (excluding the Caribbean and the Gulf of Mexico), the North Carolina team predicted five to six hurricanes with one making landfall. In fact, four hurricanes formed in the Atlantic to the east of the U.S. and none hit the coast.

Lead researcher Lian Xie, a professor of atmospheric sciences at the university, said his team focused more on sea-surface temperatures than on El Nino. Large variations between water temperatures in the northern and southern tropical regions of the Atlantic portend more active hurricane seasons, Lian said.

“The other hurricane experts may say we’ve just been lucky – they have been doing it for over two decades and we’ve only been at it for three years,” Lian said. “The key point here is prediction of hurricane activity is very challenging work.”

Meanwhile, the scorecards for next year will soon be drawn up. The Colorado State team will issue its first forecast for the 2007 hurricane season in early December.

(c) 2006, Chicago Tribune.

Visit the Chicago Tribune on the Internet at http://www.chicagotribune.com/

Distributed by McClatchy-Tribune Information Services.

AP-NY-11-18-06 1422EST

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