Wilma drenches New England

Wilma continues racing northeast at 55 mph towards Canada, and is still maintaining Category 2 winds of 100 mph. Wind shear of 50 knots is beginning to take its toll, though, and the top potion of the storm is being ripped away from the surface portion, resulting in steady weakening. By tonight, Wilma will pass north of the warm Gulf Stream waters into waters of just 20 C, resulting in rapid weakening to a tropical storm and then to a regular extratropical cyclone. The forward speed of 55 mph means that the winds on the east side of the storm are blowing at 100 mph, and the winds on the west side just 45 mph--quite an asymmetry!

Wilma and New England
Today and tonight, Wilma will dramatically affect New England's weather. A separate powerful Nor'easter storm is developing next to the coast of New England, and moisture feeding back from Wilma into the Nor'easter will drench much of Rhode Island, southeast Massachusetts, and surrounding areas with 2 - 4 inches of rain. In the northern portions of Maine and New Hampshire, the precipitation will come as snow, and reach 6 - 8 inches depth. Snowfall amounts in the Adirondacks will exceed 12 inches, and heavy snow of six inches has already been reported in the Laurel Highlands east of Pittsburgh.

Winds from the combined Nor'easter/Wilma storm will reach sustained levels of 40 - 50 mph over the waters near Cape Cod, and bring wind gusts of 50 mph to New York City, Providence, and Boston. A storm surge of 3.5 feet with 26 foot waves is expected to cause moderate flooding along the coast of southeast Massachusetts, similar to what was experienced with the blizzard of December 2003. Wilma and the Nor'easter will merge on Wednesday, bringing Nova Scotia and Newfoundland tropical storm force winds, heavy rain, and coastal flooding. New England residents, take heart: the
second Nor'easter the computer models were predicting for Sunday now appears to be a non-threat. Yes, the same computer models that have trouble with long range hurricane forecasts also do poorly on winter storms sometimes!

Were the winds on Wilma's backside stronger?
I heard numerous reporters and eyewitnesses say that that after Wilma's eye passed, the winds on the back side were much stronger. A check of the wind history at Fort Lauderdale shows that this was the case there. Sustained winds peaked at 66 mph before the eye's passage, and were 69 mph after. However, most other wind traces I have examined show the opposite trend. For example, West Palm Beach reported peak sustatined winds of 82 mph before eye passage, and 76 mph after. In general, this is what we would expect, since the storm weakened as it passed over Florida. However, there were enough asymmetries caused by friction and interaction with land that some intense thunderstorms wrapped around to the back side of Wilma causing stronger winds there for some areas. In many cases, the perception that stronger winds occurred on the backside was incorrect. After a long lull, the sudden onset of hurricane force winds makes the winds seem stronger, compared to the slow build up of winds that occurs when the storm is first approaching.

Are we done with hurricane season yet?
No. Hurricane season runs through the end of November. On average, we get one tropical storm every other year between now and the end of the year. Given that this is no ordinary year, I think we can expect at least one more tropical storm. However, I do think that the hurricane season for the United States is over. An strong cold front behind Wilma has spread unseasonably cool air across the Gulf of Mexico, the Bahamas, Cuba, and into the northwest Caribbean. This cool air will significantly chill the ocean waters surrounding the U.S., making it difficult for a tropical storm to form or maintain its strength near the U.S.

Tropical disturbance north of Panama
While hurricane season may be over for the U.S., it is definitely not over for the Caribbean. A tropical disturbance in the extreme south central Caribbean north of Panama bears watching this week. Currently, the cloud pattern is disorganized, and wind shear values of 20 knots are too high to allow development. However, wind shear values are expected to drop the next few days, possibly allowing some tropical development to occur later in the week. Most of the global forecast models predict that a tropical depression will form in this region later this week. Any development in this region would be a threat to Costa Rica, Nicaragua, northeast Honduras, and the islands to their north.

Jeff Masters