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 , 9:27 PM GMT on October 23, 2005
Wilma has entered a slow intensification phase the past three hours. The pressure has fallen from 963 mb to 959 mb, the eye has shrunk in diameter from 60 nm to 45 nm, and satellite imagery shows cooling cloud tops in the eyewall region--all signs of an ongoing intensification cycle. In response to this intensification cycle, the Hurricane Center has now upped their forecast of the maximum storm surge from 13 feet to 17 feet over southwest Florida. At the current rate of intensification, Wilma could become a Category 3 hurricane with 115 mph winds by midnight.
This intensification phase should slow down or reverse by midnight, since shear is now increasing over the storm. Shear is now about 15 knots, up from 10 knots this morning. The hurricane hunters noted that strong westerly winds aloft have pushed the top of the storm eastward, so that the area of calm in the eye at 10,000 feet is about ten miles east of the surface calm area. This stretching is also beginning to be evident on satellite images, with the shape of the hurricane appearing less circular. Assuming that the shear begins weakening the hurricane at midnight, only six or eight hours remain for the shear to weaken the hurricane before landfall at 6 am or 8 am Monday morning. This may not be enough time to weaken the storm much, so I am still anticipating a 105 mph Category 2 hurricane at landfall. By the time Wilma crosses the Florida Peninsula and arrives at the east coast of Florida, she should have top winds of about 85 mph.
The remainder of my discussion from noon today appears below, unchanged.
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 back with an update in the morning, or later tonight if events warrant.
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