For the first time in 17 years, the hurricane season has gone 97 days without a hurricane, and scientists don?t know why. The last time the Atlantic-Caribbean season ran this long with no hurricanes was 1984, until Hurricane Diana arrived on September 10. This year there have been five tropical storms but none have developed the 74 mph winds necessary for them to be classified as hurricanes. Scientists had been predicting a major hurricane season.
Tropical storm Erin?s winds have dropped to 45 mph and little change in strength is expected as it passes north of the Leeward Islands in the next few days. The hurricane situation could still change rapidly since there is still a lot of hurricane season left. It runs from June 1 through Nov. 30, with most of the activity going on from mid-August until the end of October.
With such a late start, a big year is unlikely, according to Hugh Willoughby, director of the National Oceanic and Atmospheric Administration?s hurricane research division in Miami. ?The experience is that with a late start, one that comes after Sept. 1, you can still have an average season,? he says. ?What you don?t get is an above-average season.?
Long-range forecasters predicted 12 tropical storms, seven hurricanes and three major hurricanes this season. Even in an average year there would have been two hurricanes by now and one of them would have been major, with winds of more than 110 mph. Most of the elements are in place for the development of hurricanes, which is why forecasters are so puzzled. Tropical waves that normally produce tropical storms and hurricanes are coming off the African coast at the usual rate, and upper level winds that can shear the tops off tropical systems are no more frequent than usual.
?If you use the usual parameters to predict formation and intensification, everything looks good,? says forecaster Lixion Avila of the National Hurricane Center. ?But obviously something is going on. There?s a mystery reason out there.? Meteorologists feel we are in a period of heightened hurricane activity that could last for decades, and if this year stays below average, it doesn?t change the long-term trend.
Insight: The stratosphere has been warming dramatically in recent years, and there may no longer be enough temperature difference between it and the air at ground level to generate normal hurricanes. However, atmospheric levels above the stratosphere are cooling even more dramatically, and if a storm ever reaches that high, it could become very powerful. Fewer but stronger hurricanes might be on the cards.
NOTE: This news story, previously published on our old site, will have any links removed.