April 20, 2005

Scientists Devise New Hurricane Forecast

British scientists say they have devised a more accurate way to forecast whether the United States is in for a particularly damaging Atlantic hurricane season.

The new computer model, developed by climate researchers at University College in London, measures the intensity of the trade winds and the temperature of the water in July to predict whether it is going to be a busy hurricane season and whether those storms will tend to reach land or stay out at sea.

The researchers reported that the model correctly predicted the unusually active 2004 hurricane season, when Florida and other Southern states were pummeled with five hurricanes in a row - Alex, Charley, Frances, Ivan and Jeanne.

The model was also tested against annual storm data from 1950 to 2003, and correctly predicted 74 percent of the time whether the number of hurricanes hitting land would be higher or lower than normal, the researchers said.

The new method does not predict precisely where storms will strike. But even a more generalized forecast could help protect lives and reduce damage, they said. Details appear in Thursday's issue of the journal Nature.

Other hurricane forecasters said the method devised by Mark A. Saunders and Adam S. Lea of the Benfield Hazard Research Centre is a sound contribution.

"Their forecast looks to show moderate skill over the past 54 years," said Phil Klotzbach, a research associate with the Colorado State University.

Every year, the Colorado group issues a hurricane forecast for the Atlantic basin based on El Nino activity in the Pacific, drought in Africa and other factors.

In the new method, the researchers measure the irregularities and intensities of winds generated in atmospheric layers ranging from about 2,400 feet to 24,000 feet above sea level in six regions over the North Atlantic and the eastern Pacific. Winds in these regions influence the energy of hurricanes spinning in the Atlantic and steer storm systems toward land.

The researchers found that weaker-than-normal trade winds and warmer-than-normal water favor the formation of intense hurricanes.

The Atlantic hurricane season begins June 1 and runs through November. In 2004, there were 16 named storms, eight of them reaching hurricane strength. The average is about 10 a year, with six becoming hurricanes.

The cycle of hurricane strength appears to flip every 30 years and since 1995 active seasons have been the norm.

This year, the Colorado State group foresees 13 named storms in the Atlantic, including three intense hurricanes. The British group will make its 2005 forecast on Aug. 4. Most Atlantic hurricanes that strike land develop after Aug. 1.


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