Article from: NATIONAL GEOGRAPHIC
October 2000

In Hurricane Alley - How Strong Will The Winds Get?

A hurricane affects its own intensity by interacting with the ocean," says Isaac Ginis, an oceanographer at the University of Rhode Island. This is how it happens: Warm water at the top of the ocean fuels a hurricane. As it spins, the hurricane churns the water beneath it, bringing cooler water up from the depths (See figure 1). The cooler the water that it brings up, the less fuel the hurricane has. In the Caribbean, where even the deep water is warm (See figure 1) hurricanes tend to be more powerful.

Figure 1

In the Gulf of Mexico (See figure 2), where the warm layers of water are shallower, "hurricanes essentially kill themselves." explains Ginis. In September 1998 Hurricane Gilbert illustrated that difference, reaching wind speeds of more than 175 miles an hour early on but wakening once it moved across the Yucatan Peninsula into the Gulf.

Figure 2

Traditional predictions of hurricane intensity have been based primarily on changes in the atmosphere. Taking into account subsurface sea temperatures, Ginis created a model that improved intensity forecasts by 30 percent last year. "The U.S. spends $700,000 a mile to prepare a coastal area during a hurricane warning," he says. "A more skillful forecast will reduce the size of the area on alert, so we're talking about big potential savings."