A Warm Atlantic Stokes Hurricane Fears

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July 14, 2010, 11:50 am
A Warm Atlantic Stokes Hurricane Fears
By JOHN COLLINS RUDOLF

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http://green.blogs.nytimes.com/2010/07/14/a-warm-atlantic-stokes-hurricane-fears/


Stretching from the coast of West Africa to the Caribbean is a band of warm water several hundred miles wide where most Atlantic tropical storm systems “spin up,” gaining speed and size as they move toward the eastern seaboard and the Gulf of Mexico.

Meteorologists are watching these waters closely this year as satellite measurements show surface temperatures to be abnormally high — one of several signatures of a busy hurricane season to come.

These warm waters are one reason the National Oceanic and Atmospheric Administration warned in May that this year’s Atlantic hurricane season might well be one of the busiest on record, with 14 to 23 named storms.

Bracing for possible impact are two areas already battered by catastrophe: the Gulf Coast, struggling to clean up oil from BP’s out-of-control well, and Haiti, where reconstruction after January’s earthquake remains a slow work in progress.

Satellite measurements show water temperatures throughout the band are between one to two and a half degrees Fahrenheit above a recent 30-year average, according to data from Climate Central, a climate news and research organization. Data from NASA shows similar above-average temperatures.

“It’s anomalous,” said David D. Adamec, a NASA oceanographer. “In the likely hurricane formation areas, it’s warmer than normal.”

The added heat serves as fuel for hurricanes, which gather strength as they pass over warmer waters.

Another factor driving forecasts of a busy hurricane season is the predicted arrival of cooler-than-normal water temperatures in the equatorial Pacific ocean, a weather pattern known as La Niña, by late summer.

During El Niño years, warm waters in the Pacific create wind shear (essentially high-altitude countervailing winds) in the Atlantic, which can disrupt and destroy even the most powerful hurricanes. Without strong wind shear, hurricanes can develop on a near-vertical axis and grow extremely powerful.

The Atlantic has already seen its first hurricane, Alex, which swept into the Gulf of Mexico and made landfall largely in Mexico. But if history is any guide, the storms to watch will come in August and September — and will form not in the Caribbean, but over Africa.

These systems typically begin in inland West Africa, then gather strength as they sweep into the eastern Atlantic, often over the Cape Verde islands. These “Cape Verde” storms can be extremely dangerous, as they gather strength through weeks of travel over warm equatorial waters before finally reaching the Eastern seaboard.

Of course, hurricane prediction is an inexact science, and an abrupt change in weather patterns could cause this year’s storm season to fizzle. But for now, all indicators point to a season of strong storms — perhaps even one on par with 2005, which generated some of the most powerful systems on record, said Greg Holland, an atmospheric scientist at the National Center for Atmospheric Research in Boulder, Colo.

“The atmosphere is a fickle beast — it can point itself in one direction and then change,” Mr. Holland said. “But everything we’re seeing is more extreme than in 2005.”

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