About Jeff Masters
Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather
By: Dr. Jeff Masters , 2:21 PM GMT on October 21, 2005
Hurricane Wilma's western eyewall is battering Cozumel Island today with sustained winds of 145 mph. Cancun radar shows the west eyewall touching Cozumel, and some intense rainbands affecting Cancun and the northeast tip of the Yucatan Peninsula with rains of over one inch per hour. Wind measurements from the Cancun and Cozumels airports are not available, and we have to rely on the hurricane hunters for wind information. The latest aircraft report at 6:10 am showed no signs that the storm was weakening yet, and Wilma still has a few hours to intensify slighty before the center moves over land.
As Wilma continues north-northwest at 4 mph today, the large eye of the storm should come ashore near Cancun, bringing enormous devastation to the 50-mile wide section of coast exposed to the intense winds of the hurricane's eyewall. A long period of calm lasting up to seven hours will accompany the passage of the slow-moving eye, givng residents the only respite from the storm they are likely to get for the next two days. During these next two days, Wilma will wander erratically over or just offshore the Yucatan. This will expose structures in the hurricane zone to very long duration hurricane force winds, creating far more destruction than Category 4 Hurricane Emily did earlier this year, or Category 5 Hurricane Gilbert in 1988. Wilma may be Mexico's most expensive hurricane disaster ever. Wilma's rains will add to the misery, reaching 20 inches or more over not just the Yucatan, but the western tip of Cuba as well.
Figure 2. Computer model tracks for Hurricane Wilma.
How will Wilma affect Florida?
During the next two days, steady weakening of the storm should occur due to interaction with land. In addition, wind shear and dry air are beginning to increase over the northwest side of the storm, and should work together to steadily reduce Wilma's strength. When the trough of low pressure expected to pick up Wilma finally does sweep her east towards Florida, wind shear will be quite high and increasing, leading to continued steady weakening. The final strength of Wilma at landfall in south Florida could still range from Category 3 to tropical storm. It all depends upon how much time Wilma spends over water. If the UKMET model is right, Wilma will spend very little time over land, and arrive at Florida as a Category 3 hurricane. If the GFDL model is right, Wilma will spend more than two days over land and weaken to a tropical storm, and eventually move across Cuba as a tropical storm, missing Florida entirely.
Given all these factors, I don't see any reason to change the range of probabilities I gave yesterday for Florida. I'd give Wilma a 10% chance of arriving on the Florida west coast as a Category 3 or higher storm, 20% as a Category 2, 40% as a Category 1, and 30% as a tropical storm. On Florida's east coast, knock these value down by half a Category (10 - 15 mph).
The timing of this expected blow on Florida is still difficult to pin down. Some models are now indicating Wilma may not hit Florida until Tuesday. What are the chances that Wilma will somehow move north and affect the Florida Panhandle, or portions of the Gulf Coast further west? Less than 1 in 1000. As we approach winter in the Northern Hemisphere, westerly winds associated with the Jet Stream move far to the south, making it very difficult for any storm to go any direction but east or northeast once it gets into the Gulf of Mexico.
After Florida, then what?
There is no change to the forecast. After crossing Florida, Wilma should bring tropical storm force winds to the northern Bahama Islands. Wilma should pass well offshore North Carolina, but close enough to bring tropical storm force winds to the Outer Banks. Wilma is expected to merge with a large low pressure system as she approaches Maine or Nova Scotia next week, and could bring tropical storm force winds to Cape Cod, Maine, and the Canadian Maritime provinces.
What's behind Wilma?
There is a large area of disorganized thunderstorms near 13N 63W, about 500 miles south-southeast of Puerto Rico. This area has gotten better organized since yesterday, and has some potential for slow development as it moves northwest towards Haiti. This system is primarily a threat to Haiti, eastern Cuba, and the Bahamas, and should recurve out to sea thereafter.
I'll be back this afternoon with the lastest. The Mexican weather service's web site is overloaded, so I am not including any links pointing to Cancun radar or other Mexican weather data.
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