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Disorganized Noel still dumping heavy rains

By: Dr. Jeff Masters, 8:59 PM GMT on October 29, 2007

Tropical Storm Noel's center is back over water this afternoon, near the eastern tip of Cuba. An encounter with the mountains of Hispaniola has left Noel very disorganized. Top winds from this afternoon's hurricane hunter flight were in the 45-50 mph range, and the pressure was a high 1001 mb. Noel's prodigious rains of over one inch per hour have slowed to 1/2 inch per hour, according to satellite estimates. Long range radar out of Puerto Rico shows heavy rains affecting the Dominican Republic and western Puerto Rico. These rains have already exceeded eight inches over a wide area of ocean to the east of Noel's center, according to rainfall estimates from the Puerto Rico radar. Rainfall amounts of 4-8 inches over southern Puerto Rico have triggered numerous flash floods and landslides. The Holguin, Cuba radar shows spiral bands of heavy rain affecting the eastern part of Cuba and the easternmost Bahama Islands.

Flooding on Hispaniola
Noel has increased it's forward speed, but heavy rains will continue to affect Hispaniola for two more days, and the flooding situation will be extremely serious on the island. Satellite loops show very vigorous thunderstorms reaching high into the atmosphere continue to stream over Hispaniola. These thunderstorms dumped about 175 mm (7 inches) of rain in the past 24 hours near the capital of the Dominican Republic, Santo Domingo (Figure 1).

So far, Haiti has escaped the worst of Noel's heavy rains, giving hope that a repeat of the floods triggered by Hurricane Jeanne in 2004 might be avoided. Jeanne passed just north of Haiti as a tropical storm, and dumped about 13 inches of rain over the northern mountains. The resulting floods killed over 3,000 people. However, satellite images show a large region of disturbed weather to the southeast of Hispaniola associated with Noel, and Noel's counter-clockwise circulation will pull heavy rains over Hispaniola for the next two days. I expect that some regions of Haiti will receive over 12 inches of rain from Noel.

Figure 1. Satellite estimates of rain for the 24-hour period ending at 8 am EDT Monday, 10/29/07. Note the pink "bulls-eye" at upper right of the image over Hispaniola, indicating heavy rain of about 175 mm (7 inches) fell over the southern Dominican Republic. Image credit: Navy Research Lab, Monterey.

The track forecast
The latest computer model runs from 12Z this morning are in better agreement, but have shifted Noel's point of recurvature closer to South Florida. The models all forecast that Noel will follow a northwest or west-northwest track for the next 2-3 days parallel to Cuba, through the Bahamas. One key question is, what will be the timing and strength of a trough of low pressure forecast to move off the U.S. East Coast Thursday? A slower arrival of this trough will allow Noel to penetrate farther west. The other key question is, how strong will Noel be then? A weaker Noel that does not extend as high into the atmosphere is likely to make it further west. The ECMWF model forecasts that Noel will be a very shallow and weak tropical storm which will not recurve until it reaches South Florida. The HWRF is similar, forecasting a 45 mph tropical storm that will recurve about 50-100 miles off the coast of Miami. A stronger Noel will extend higher in the atmosphere, and will recurve sooner. The GFDL model forecasts Noel will strengthen into a Category 1 hurricane, and recurves Noel the farthest east, in the central Bahamas. The other models are in between.

The intensity forecast
Passage over the mountainous terrain of Haiti has severely disrupted Noel, and it will likely not start intensifying significantly until Tuesday afternoon. Wind shear is about 10-20 knots, and is expected to remain in that range over the next three days. This will allow some strengthening of Noel if its center can avoid moving over Cuba. I give Noel a 30% chance of reaching hurricane strength. After three days, wind shear is expected to increase above 20 knots, and Noel should weaken.

In summary, if Noel does make it all the way to South Florida, it will probably be as a weak tropical storm. If Noel strengthens significantly, it is likely to recurve sooner. It could be a windy trick-or-treat time in Miami Wednesday night.

The NOAA jet is scheduled to make its first flight this evening, so we should have a set of high-quality model runs to look at first thing Tuesday morning, when I'll post my next update.

Jeff Masters

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