for National Geographic News
Meteorologists think a decade-long trend of active Atlantic hurricane seasons will continue this summer. That's bad news for U.S. coastal residents who took a 45-billion-dollar (U.S.) pounding from the storms last year.
Forecaster William Gray of Colorado State University expects a busy summer in the Atlantic Basin, which includes the Gulf of Mexico and the Caribbean Sea. Gray, a pioneer in long-range hurricane forecasting, thinks eight hurricanes will form during the season, which officially began today and runs to November 30.
Gray said four of those storms will become major hurricanes, with winds exceeding 111 miles an hour (178 kilometers an hour).
The National Hurricane Center (NHC) in Miami, Florida, predicts seven to nine hurricanes in the Atlantic Basin, with three to five of them becoming major hurricanes.
Hurricanes begin as tropical storms. A tropical storm becomes a hurricane when its winds reach 74 miles an hour (119 kilometers an hour). Gray thinks 15 tropical storms will form, while the NHC expects 12 to 15.
"Many climate signals, such as warmer-than-average water in parts of the Atlantic Ocean, indicate the likelihood of an active 2005 Atlantic hurricane season," said meteorologist Stu Ostro of the Weather Channel. "That's why many of those who issue seasonal outlooks are predicting an above-average number of tropical storms and hurricanes."
More Salt, More Storms
Gray and NHC meteorologist Chris Landsea think the busy hurricane seasons in recent years are part of a well-established cycle of fluctuations in the temperatures of ocean waters.
The variances in seawater temperatures are related to periodic changes in ocean currents that affect the salt content of the water, Gray noted. Hurricanes draw their energy from warm ocean water.
When the salt content increases slightly in the Atlantic Basinas it has nowthe water is a little warmer, and that tends to produce more hurricanes, Gray said.
Another variable in the creation of hurricanesdecreased upper-level atmospheric windsis also favorable to storm formation. During inactive seasons, these winds often tear apart hurricanes as they try to form. But for the past few years the winds have been minimal, and more hurricanes have formed.
Gray thinks there's a 77 percent probability that a major hurricane will make landfall somewhere on the U.S. coast this summer. He puts the chances of the Florida peninsula taking a hit at 59 percent, or 28 percentage points above the normal risk. The Gulf Coast has a 44 percent chance, compared to a 30 percent chance normally, Gray said.
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