Storm season's second phase not far away
Atlantic climate often shifts in October - good news for Florida but not for Caribbean.
By almost any human measure, the 2004 hurricane season has brought enough exasperation and destruction to fill an entire decade. By the unforgiving eye of science, however, this year's hurricane season still has more than two months to go.
As Jeanne spun into shreds Monday over Georgia, meteorologists were already turning their attention back to the open Atlantic to see what might come next out of West Africa's hurricane nursery.
For Florida's wind-weary residents, perhaps, the deadline of note is Oct. 10, when the climate in the Atlantic generally changes, moving hurricanes into the Caribbean - and more toward Central America. But this season has already served notice: The Atlantic is in the midst of a 20-year upswing in hurricane activity, and while a peculiar set of conditions has funneled four storms directly toward Florida, the broad pattern of increased activity is far from over.
"It's reasonable to assume above-average years for another 10 years," says Gerry Bell, a meteorologist at the National Weather Service's Climate Prediction Center.
This hurricane season has been unusual even in a time of greater activity, with 12 named storms and seven hurricanes already. With two months remaining, it could end up rivaling 1995 - the second most active hurricane season on record.
It's noteworthy "in terms of the overall number, the intensity [of the storms], and their duration," says Dr. Bell.
While Ivan was by far the strongest, Jeanne has been remarkable in its endurance, tracking through the Caribbean before circling, regathering strength, and bearing down on Florida. By Monday morning, six people had died in the hurricane and some 2.6 million homes and businesses had lost power. The relief efforts for Jeanne and other three hurricanes to hit Florida in the past six weeks represent the largest in United States history - surpassing the efforts made after the 1994 Northridge earthquake in Los Angeles.
Not only have four hurricanes hit Florida this season - the first time since 1886 that four hurricanes have hit a single state in a season - but they have followed strikingly similar routes. Jeanne and Frances came ashore virtually in the same neighborhood.
The main reason for that is the continued and abnormal strength of the Bermuda High - the high-pressure zone bounded to the south by an air current from Africa and to the north by a current from the north pole. The two currents come to a point off the American mid-Atlantic coast.
So long as the Bermuda High remains strong, hurricanes will trundle along its underside like bumper cars until they reach the American coast, then head north after they round the point of the triangle. Usually, though, the Bermuda High weakens, allowing hurricanes to veer north while still far out in the Atlantic.
This summer, the Bermuda High has stayed strong, bringing hurricanes right to Florida's doorstep before they round the corner and rake northward across the American South.
"So long as the steering patterns stay in effect, it will allow the landfall patterns to continue," says Erica Rule, a spokeswoman for the Atlantic Oceanographic and Meteorological Laboratory in Miami.
How long those steering patterns stay in effect is anyone's guess. Even though there are only two weeks left in peak hurricane season, scientists won't even cast predictions that far. Meteorological forecasts only can look a week ahead with any sense of accuracy.
What meteorologists will predict is that, regardless of where the hurricanes go, there will probably be more of them than normal again next year. The rise isn't believed to be connected with global warming. It's a well-established cycle of relative calm followed by increased activity - often flip-flopping every 20 to 25 years.
The current period of heightened activity appeared to begin in 1995. The Atlantic has spawned five major hurricanes in a season four times since 1995 - including this year. Before that, there were only three seasons of above-average activity in 25 years. Typically a season has six hurricanes, two of them major.
Moreover, scientists say, this year is far from finished. Seasons of high activity tend to remain active until the end - Nov. 30. But in mid-October, the focus will shift from the Atlantic to the western Caribbean. Although these storms tend not to threaten the US, they can be as powerful as the storms that form in the Atlantic - and grow much more quickly.
The classic late-season storm was hurricane Mitch, which hit Central America in late October 1998.
The only asterisk in meteorologists' predictions of above-average hurricane activity - for the remainder of this year and for next year - is El Niño. Though El Niño is a Pacific weather pattern, it tends to soften Atlantic hurricane seasons. Scientists are seeing evidence that El Niño is growing, a trend that could slow hurricane growth if it continues.
"There's a small possibility that it could get strong enough to reduce any late-season activity," says Bell.