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 , 4:03 PM GMT on October 23, 2005
Wilma is ending its long pounding of Mexico's Yucatan, and is now steadily accelerating towards its next target--southern Florida. The eye has been offshore the Yucatan for about 12 hours now, but no intensification has occurred--yet. The latest hurricane hunter flight, at 11 am EDT, found a central pressure of 964 mb, up 3 mb from the previous flight at 7 am EDT. Wilma has a very large 70 mile diameter eye, thanks to the collapse of the inner eyewall during passage over the Yucatan.
Data from satellites, Cancun radar, and the hurricane hunters all show that the inner eyewall is now re-establishing itself over the warm waters of the Gulf of Mexico. This inner eyewall has a diameter of about 12 miles, and if it has time to fully form, could generate Category 3 hurricane winds at landfall in southwest Florida. Wind shear over Wilma is currently about 10 knots--the same level we've seen for the past few days. This shear is expected to remain at this level until about midnight tonight, and allow intensification until then. Thereafter, the wind shear will steadily increase, putting an end to Wilma's intensification phase and probably weakening her just before landfall on Monday. Wilma's size and fast forward motion may not give the shear much chance to weaken her significantly, and there is still about a 10% chance that Wilma could hit Floridsa as a Category 3 hurricane. However, given the limited time Wilma has to re-establish her inner eyewall, and the significant shear expected to assert itself, the most likely intensity at landfall is a Category 2. A Category 1 storm at landfall is a good possibility, as well. Ordinarily, the crossing of the Florida Peninsula should weaken a hurricane by about 10 mph, but in Wilma's case, her winds should be 15 - 20 mph weaker on the east coast of Florida, due to the extra time significant wind shear will have to weaken her.
Assuming my forecast of a landfall near Marco, Florida as a Category 2 hurricane with 105 mph winds is a good one, we can expect a storm surge of 8 to 14 feet near that city and to the south. The Keys would see storm surge flooding of 5 to 8 feet. Fortunately, the area south of Marco is primarily uninhabited--the Everglades swamp. However, if Wilma comes ashore north of Naples--or further south near the Keys--storm surge flood damage in those areas could easily reach billions of dollars. Storm surge flooding should be only 2 - 4 feet on the east coast of Florida, where wind damage is the primary threat.
Figure 1. Storm surge map for southwest Florida.
Wilma's winds and rain
Wilma will be moving too fast to dump more than 5 - 10 inches of rain. The rain will be concentrated on the north side of the hurricane, since there will be a cold front there that will trigger more condensation. Areas to the north of the eye's passage will see winds a full Category--25 to 30 mph--lower than those on the south. This is because the storm's high rate of forward motion, near 25 - 30 mph, will add to the windspeeds seen on the south side of the Wilma's counterclockwise rotation, and subtract on the north side. Since the storm will be moving so fast, the duration of hurricane force winds will be just a few hours.
After Florida, then what?
After crossing Florida, Wilma should bring 50 - 60 mph winds to the northern Bahama Islands, but not hurricane force winds. Wilma should pass close enough to North Carolina's Outer Banks to bring 40 mph winds there and up to an inch of rain. It now appears that Wilma will bring 40 mph winds and 1 - 3 inches of rain to southeast Massachusetts, along with 20 foot waves. Boston, which has already had its fourth wettest October ever with 7.52 inches of rain, may break its October record. Nova Scotia will probably bear the brunt of Wilma's fury, receiving a direct hit by the center, along with 45 - 55 mph winds and rains of 3 - 5 inches.
Tropical Storm Alpha, the record-breaking 22nd tropical storm of this unbelievable hurricane season, has come ashore over Haiti and the Dominican Republic. Heavy rains of up to 12 inches could cause heavy loss of life in Haiti, where 98% deforestation rates have left the island highly vulnerable to flooding from even ordinary fast-moving tropical storms like Alpha. In the event a major flood disaster does ensue, dictating the retirement of Alpha's name, there are no contingency plans on how to replace Alpha's name on the list. Alpha is moving fast enough that I am hopeful a major flooding disaster will be averted in Haiti, though.
The 10,000 foot high mountains of Hispanolia have seriously disrupted the circulation of Alpha, making it questionable how much will remain of the storm to threaten the Turks and Caicos Islands. In any event, Alpha does not have long to live, as the huge circulation of Hurricane Wilma will overtake it by Tuesday and destroy the storm with high wind shear.
I'll be watching Wilma this afternoon, and will have a new report by 5 pm.
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