Wilma Worries Islands, N. Orleans

Nagin Tells Residents To Be Ready To Evacuate If Storm Strengthens And Heads For Big Easy

(CBS/AP) 
Since 1995, the Atlantic has been in a period of higher hurricane activity. Scientists say the cause of the increase is a rise in ocean temperatures and a decrease in the amount of disruptive vertical wind shear that rips hurricanes apart. Some researchers argue that global warming fueled by man's generation of greenhouse gases is the culprit.

Forecasters say the busy seasons are part of a natural cycle.

"Between the 70s and 80s, there was relatively light activity, and now in the 90s and 2000s, we've seen this increased cycle, so we're in it for the next 10-15 years at least," meteorologist Ron Goodman told CBS Radio News.

It's also difficult to know whether the Atlantic was even busier at any time before record keeping began in 1851. And satellites have only been tracking tropical weather since the 1960s, so some storms that just stayed at sea before then could have escaped notice.

The six-month hurricane season ends Nov. 30. Wilma is the last on the list of storm names for 2005; there are 21 names on the yearly list because the letters q, u, x, y and z are skipped.

"If we happen to have to go to another storm, we go to the Greek alphabet, so the next storm would be Alpha, and then Beta and Gamma," said CBS News meteorologist George Cullen.

That has never happened in roughly 60 years of regularly named Atlantic storms.

A tracking map on the hurricane center's wall already had Alpha, Beta, Gamma and Delta listed just in case they form.

Forecasters say they wouldn't be surprised if another storm formed this year, even though the official forecast only called for 21 named storms this year. Wind shear typically increases and sea temperatures usually fall toward the end of October in the Atlantic, hurricane specialist Richard Knabb said.

"But the western Caribbean is an especially favorable location for late season development because the water remains quite warm and the vertical shear often is not that strong down there, that far south. So conditions are still favorable down there sometimes in late October and into November," he said.