Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.
By: Dr. Jeff Masters , 10:59 AM GMT on October 19, 2005
There has never been a hurricane like Wilma before. With an unbelievable round of intensification that saw the pressure drop 87 mb in just 12 hours, Wilma smashed the all-time record for lowest pressure in an Atlantic hurricane this morning. The 4 am hurricane hunter report put the pressure at 882 mb, easily besting the previous record of 888 mb set in Hurricane Gilbert of 1988. And since no hurricane hunter airplane has been in the eye since then, Wilma may be even stronger now. The eye diameter of Wilma during this round of intense shrunk as low as 2 nautical miles, which may be the smallest eye diameter ever measured in a tropical cyclone. The only eye that small I could find in the records was a 3 nm the Category 4 Typhoon Jeliwat achieved in 2000. It's amazing the hurricane hunters were even able to penetrate the eye--it's really tough to hit a 2 mile wide eye when you're flying crabbed over at a 30 degree yaw angle fighting horizontal flight level winds of 185 mph and severe turbulence. This is an incredibly compact, amazingly intense hurricane, the likes of which has never been seen in the Atlantic. The Hurricane Season of 2005 keeps topping itself with new firsts, and now boasts three of the five most intense hurricanes of all time--Katrina, Rita, and Wilma.
Where will Wilma go?
There is a lot of uncertainty about this, as usual. After last night's flight by the NOAA jet, the computer models have come into better agreement, forecasting a track northwest through the Yucatan Channel, and then northeast across southern Florida. Cuba will probably end up getting the worst of Wilma, particularly the western tip of Cuba, which could see a direct hit.
After Cuba comes Florida. The models are converging on a landfall over the sparsely populated Everglades, but Wilma could hit as far north as Sarasota or pass south of the Keys. In any case, I expect the evaction order for non-residents in the Keys will be given today, and the Keys and residents of southwest Florida from Naples southward are at greatest risk from Wilma. Assuming Wilma does hit the Everglades as expected, the Gold Coast of Florida from Miami to West Palm Beach are in for a severe pounding after Wilma crosses south Florida.
How strong will Wilma be?
Hurricanes do not maintain Category 5 strength very long, and Wilma is unlikely to be at that strength when it clears the Yucatan Channel and turns northeast towards Florida. Combine with that the possible effects of weakening due to interaction or a landfall on the western tip of Cuba or the northeast tip of the Yucatan Peninsula, and Wilma is likely to be a Category 3 or 4 hurricane as it starts bearing down on southwest Florida. When Wilma does make this turn, the winds that will be turning her will also be creating some significant wind shear, which will weaken the storm. Wilma will be moving fairly quickly, though, so the shear won't have a lot of time to weaken her. I'm guessing this weakening will be in the order of 10 - 20 mph.
The end result of all these factors will cause Wilma to hit southwest Florida in the Everglades as a Category 3 or weak Category 4 hurricane with winds in the 120 mph - 135 mph range. The Everglades are low and swampy, and passage over the this area does not weaken a hurricane as much as landfall further north over the Florida Peninsula. In the case of Hurricane Andrew, which passed across the Everglades on a reverse path, the hurricane started its traverse as a Category 5 hurricane with 170 mph winds and a 922 mb central pressure. By the time it emerged in the Gulf of Mexico, Andrew was a Category 3 hurricane with 130 mph winds and a central pressure of 951 mb. Andrew was a very small hurricane, and passage over the Everglades weakened it considerably. In the case of Hurricane Katrina earlier this year, the traverse of south Florida did not
significantly weaken the storm. Katrina started its traverse of south Florida with a central pressure of 981 mb and 75 mph winds, and finished with a central pressure of 985 mb and 75 mph winds. Katrina was a much larger storm than Andrew, and more representative of the size Wilma is likely to have over Florida.
The closest analogue storm I can find in the archives to Wilma is an href=http://www.wunderground.com/hurricane/at190608.asp>October 1906 hurricane that looks remarkably similar. The 1906 hurricane formed in the western Caribbean, brushed Cuba as it passed through the Yucatan Channel, then crossed extreme southern Florida, passing from the
Everglades to Fort Lauderdale. This hurricane weakened from a Category 4 hurricane with 135 mph winds to a Category 3 hurricane with 125 mph winds as it crossed Florida.
I think we can expect Wilma to behave in a similar fashion to the 1906 hurricane, and lose about 10 mph in its peak winds due to passage over the Everglades. Wilma may lose an additional 5 mph due to the continued action of the expected higher wind shear. This would make Wilma a strong Category 2 or weak Category 3 hurricane over Miami/Fort Lauderdale with peak winds of 105 - 120 mph. A really big question is how far out will the hurricane force winds extend? Wilma is currently a very compact storm with
hurricane force winds extending out only 15 miles from the center. If she maintains this compact structure, damage in Florida will be limited to a very small area. However, with three days remaining over very warm waters, Wilma will doubtless expand its windfield somewhat, so that hurricane force winds will extend out 50 - 80 miles from the center. This will be enough to cause severe damage to the Gold Coast in the $10 - $20 billion range. If Wilma follows the path I expect, this will be the worst hurricane in Miami Beach/Fort Lauderdale area since 1965's Hurricane Betsy.
Keep in mind that the average error in a hurricane track forecasts four days is over 200 miles, and that our skill in making intensity forecasts is low--as witnessed in Wilma's incredible ascent from a Category 1 to Category 5 hurricane in just 12 hours.
What has Wilma done so far?
Wilma has claimed her first victims; up to ten are dead on Haiti in landslides triggered by the hurricane's heavy rains. Mudslides and flooding are also serious problems in the southeastern Cuban provinces of Guantánamo, Santiago de Cuba and Granma. Nearly 13 inches (33 cm) of rain was measured at Santiago de Cuba yesterday. The Cuban newspaper Granma is reporting 255 homes damaged or destroyed in that town, and sections of the Sevilla-Guamá-Santiago de Cuba highway impassable due to swollen rivers, while landslides have blocked the Cordovelo-Loma Blanca road. In Jamaica, widespread flooding has cut off several communities and caused millions in damage to roads. All schools are closed on the island through Thursday and hospitals are taking only emergency patients. Rainfall rates as high as two inches per hour were observed in the Blue Mountains of south-central Jamaica yesterday.
I'll have another update this afternoon, there's a lot more to talk about.
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