Storm cycle spawning abundance of hurricanes

July 17, 2005|By Frank D. Roylance | Frank D. Roylance,SUN STAFF

Surely no one with a working TV set has missed the news: We have had an extraordinary start to the 2005 Atlantic hurricane season.

Already, tropical storms Arlene, Brett and Cindy have boiled out of the Caribbean Sea, the first of them barely a week after the season officially opened on June 1.

Then came Dennis on July 6, the first storm this year to reach hurricane strength. It left 20 people dead across the Caribbean. And twice it spun into a fearsome Category 4 storm, with 135 mph winds, before finally wheezing, weakened, into the Florida panhandle.

Now it's Emily, yet another hurricane, born in the tropical Atlantic on July 10 and churning across the Caribbean this weekend toward Texas and Mexico.

It's been the busiest start to a hurricane season on record, and it follows a punishing season in 2004. Four hurricanes made landfall in Florida in just six weeks last year. They killed 152 people, demolished 27,000 homes and caused $45 billion in property damage.

Extraordinary for sure. But does it suggest anything about the rest of this season, or about the threat from the tropics in the years and decades ahead?

Meteorologists say they saw it all coming. It's part of a well-understood cycle of ocean temperatures, salinity and winds that have produced such periods of unrest in the tropics before.

But while some scientists, laymen and politicians may go further and draw connections between the stormy weather and global warming, others say the science is less convincing.

"There may certainly be a connection, but I don't think at this point it's been firmly established," says Colin McAdie, a National Hurricane Center meteorologist. The issue is complex, "and I'm not sure at this point we really have the final answers."

What forecasters do seem to have nailed were their predictions for an active 2005 hurricane season. "Our seasonal forecast several months ago was calling for an above-average season," McAdie says. "That forecast is being borne out."

When Emily reached tropical storm strength (39 mph) on July 11 and earned her name, the experts said it marked the first time -- at least since the National Weather Service began naming tropical storms systematically in 1951 -- that five Atlantic storms powerful enough to get names had developed so early in the season.

But a blustery start does not guarantee how the season will look when it officially ends on Nov. 30.

"There's very little relationship between the activity in the early part of the season and the activity in the main, or even the late part of the season," says Jim Elsner, professor of geography at Florida State University.

For example, the 1997 season got off to a pretty fast start, too. By July 16 that year, there were already four named storms and one unnamed sub-tropical storm on the books.

"But that season turned out to be not very active," he says. El Nino interfered, and it ended with just seven named storms. Only three became hurricanes, and just one touched the U.S. mainland.

Last year, too, was forecast to be an active season. The first named storm --Alex -- didn't appear until July 31, and the questions meteorologists fielded then were, "How come nothing's happening? What does it mean?"

"We said it doesn't mean anything," Elsner recalls. "And of course, things happened rather explosively after that." Seven named storms popped up in August, and seven more after that.

Still, while this year's fast start doesn't necessarily guarantee the 2005 season will stay busy, there are signs that suggest it will, forecasters say.

"The thing that's a little different this year is we are seeing early activity, and some systems, coming out of the deep tropics," McAdie said.

To forecasters, the "deep tropics" means south of 20 degrees north latitude. Dennis and Emily both were spawned in those latitudes -- Dennis in the southeast Caribbean, and Emily in the Atlantic.

It's a region that typically produces the most powerful storms, but usually not before the middle of the hurricane season -- mid-August through September.

That it's already begun, McAdie says, "is suggestive of a more active, or possibly even hyperactive season. We'll have to see how it plays out."

"Active" is what hurricane prognosticators have been predicting, at least since May.

Satellites and ocean buoys are reporting that sea surface temperatures in the Atlantic basin -- which includes the Caribbean where Emily is now spinning -- remain unusually warm, a heat engine for hurricanes.

There's also no El Nino this summer in the eastern tropical Pacific. If there were, any storms that did form in the Atlantic and the Caribbean might be cut down in their youth by the shearing winds that flow out of the Pacific during an El Nino event.

These hurricane-friendly conditions have dominated for a decade now. Since 1995, the average number of major hurricanes spinning out of the tropics has been more than double the long-term average.

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