Wilma: a hurricane today

Wilma continues to intensify. Satellite imagery shows a dense cirrus overcast (CDO) beginning to form and cover the center of the storm, which is characteristic of a tropical storm intent on becoming a hurricane. Spiral banding and upper-level outflow continue to improve and cover a larger area. Some wind shear and dry air are affecting the northwest side of the storm, but Wilma is gaining a more symmetric appearance characteristic of a hurricane. The hurricane hunters left the storm at 3 am EDT this morning and are not due back until about 3 pm EDT this afternoon, so we will have to wait until then to learn Wilma's true strength.

The upper level environment continues to look favorable for intensification, with low wind shear and an anti-cyclone on top generating good outflow on all sides except the norhtwest. Intensification into a Category 3 hurricane by Thursday still seems like a good bet. There is a small chance Wilma could make it to Category 4 status by Friday, but shear will start to increase by then as the upper-level trough of low pressure generates strong westerly winds over her. This shear will likely reduce Wilma's winds by at least 20 mph, and landfall in Florida as a strong Category 2 hurricane seems like a reasonble intensity forecast.

Steering currents are expected to remain weak today, and some erratic motion is possible. All of the forecast models predict a generally west or west-northwest motion over the next two days. Now that Wilma has stopped moving south, this gives me some confidence that this forecast is the correct one, and the danger to Honduras is considerably lessened. Only the northeast portion of Honduras should see heavy rains over ten inches, and since this part of the country is relatively flat, the threat of life-threatening flash flooding and mud slides like killed thousands in Hurricane Mitch and Hurricane Fifi is low. So far, northeastern Honduras has received only one to two inches of rain from Wilma.

The country that has taken the worst pounding so far from Wilma is Jamaica, where Wilma's rains have already caused millions of dollars of damage to the road infrastructure. Widespread flooding and road blockages due to mudslides are being reported, and will continue as Wilma stays essentially stationary or moves very slowly away from Jamaica today.

Next on Wilma's hit list will be Mexico and Cuba, who have already had their share of major hurricanes this season. Mexico is still cleaning up the damage from Hurricane Emily earlier this year, and Cuba took one of its worst hurricane pouundings ever during Hurricane Dennis in July. Heavy rains in the Cayman Islands, Belize, Nicaragua, and northern Guatemala may also create local flooding problems in those nations. If Wilma grows large enough to tap the Pacific as a source of moisture, Nicaragua and Costa Rica could also experience some moderate flooding problems.


Figures 1. Computer model forecasts for Wilma.

The models have reached a strong consensus that a low pressure system currently bringing rain to the western U.S. will move east and exert a strong pull on Wilma, turning her more northwest by Thursday, through the Yucatan Channel, and then northeastward into the Florida Keys or the west coast of Florida by the weekend. Most of the guidance shows the Keys to be the primary region at risk, but the GFDL model has moved its landfall point further north with its most recent run (2 am EDT), and puts the area between Sarasota and Fort Myers in the bullseye. The NOAA jet is scheduled to makes its first flight tonight, and tomorrow morning we should have a better idea of the reliability of the current model forecasts.

Elsewhere in the tropics, there is a large area of disturbed weather midway between Africa and the Leeward Islands. Upper level winds are not favorable for development of this area, which is also too close to the Equator. I'll be back with a update in this afternoon after the Hurricane Hunters report in.

Jeff Masters