Chicago – Abnormally warm seas in the Gulf of Mexico are feeding Hurricane Rita as it churns behind another monster storm, Hurricane Katrina, that passed over the same water three weeks ago. For atmospheric scientists, the twin storms are leaving deep questions in their wake.
Researchers have been watching this year as hurricanes and tropical storms spin toward the United States, one after another, with a pattern and intensity more typical of tropical Asian typhoons.
Typically a single Category 5 storm forms in the Atlantic every three years.
But there have been four since 2003 and, in Katrina and Rita, two in the past three weeks – though Rita’s power had diminished by Friday to Category 3.
Both of those hurricanes exploded as soon as they crossed South Florida and entered the Gulf of Mexico.
“What causes it? I don’t know,” said NASA oceanographer David Adamec. “It’s one of these things that will play out in the scientific research. Is it global warming, or is it part of the normal oscillation of the atmosphere? That needs to be studied.”
What is undeniable, scientists say, is that the Gulf of Mexico is as warm as it has ever been measured, that the upper wind patterns that would neuter tropical storms harmlessly at sea are absent, and that this year’s hurricanes are forming much closer to the United States than remembered. That there are more of them in the Atlantic. That they are stronger.
Complicating the search to explain “why” is that many scientists believe there are broad cycles of intense hurricane activity every 30 to 40 years. It’s possible that 2005 is just the peak of a cycle that began a decade ago. Most agree the last major hurricane cycle ended in the 1970s.
Yet the possible impact of global warming also is being explored, and proponents say it is easy to see why: Hurricanes feed on warm water, and water temperatures – particularly in the Gulf of Mexico – have been seen rising, steadily and by fractions of a degree, for more than 30 years.
Atlantic storm records seem to support the cyclical theory. While the number of tropical storms varies widely from year to year and even between decades, the number of major hurricanes reached a peak in the 1950s and declined through the 1970s and ’80s, only to emerge with brutal storms again in the mid-1990s.
But the best Atlantic hurricane measurements only began in the 1970s with satellite observations and do not predate the 1940s, when airplanes measured the storms. Skeptics of the cyclical theory question the validity of storm observations on the ground and at sea before that.
