Newspaper article The Florida Times Union

La Nina's Offspring Grows Up to Be Floyd

Newspaper article The Florida Times Union

La Nina's Offspring Grows Up to Be Floyd

Article excerpt

Hurricane Floyd, one of the largest storms to threaten the United States this century, may be an unwelcome guest but not an unexpected one, scientists say.

La Nina, the intense upwelling of cold water off South America's west coast that began a year ago, has been the key player in weather patterns ranging from floods in the Pacific Northwest to this summer's mid-Atlantic drought. Floyd is simply La Nina's latest bit of mischief.

But while experts predicted an active hurricane season this year, they have no way of knowing exactly why or how nature can create a monster like Floyd, one of seven Category 4 hurricanes to strike land this century.

"It's the right time of year, the water is warm and La Nina is here," Florida State University meteorologist and oceanographer James O'Brien said. "But nobody can say. It's like, `How did that basketball player get to be 7 feet 4 inches tall?' The conditions were right."

Thunderstorms are a regular late summer feature of the Atlantic. Warm water gives off vapor that is picked up by warm summer air and deposited elsewhere as rain.

"This convection occurs regardless of what else happens," said Kevin Trenberth, head of climate analysis for the National Center for Atmospheric Research, in Boulder, Colo. The question is, `Are you going to have individual thunderstorms, or are they going to get together?' "

Or, more specifically, Trenberth continued, "are there disruptive winds that tear hurricanes apart" before they can form? This year the winds are not there and that phenomenon, scientists agree, is mostly La Nina's fault. So storms are likely to congregate at sea in the swirling funnels known as hurricanes in the Atlantic and typhoons in the Pacific, rotating counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere in conformity with the Earth's rotation.

The cycle that produced Floyd began in 1998 after an intense El Nino, La Nina's warm-water cousin, began to dissipate off coastal Peru and Ecuador, to be replaced by La Nina. With cold water in the Pacific tropics, the chilly, west-to-east, high-altitude winds known as the jet stream no longer sensed the kind of temperature differential that attracted them southward during El Nino. …

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