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Tropical Storm Noel dumping huge rains

By: Dr. Jeff Masters, 1:08 AM GMT on October 29, 2007

Tropical Storm Noel continues to represent a serious rainfall threat to the Dominican Republic and Haiti due to the storm's very slow motion. Noel has essentially stalled out tonight, and is dumping very heavy rains over the southernmost tip of the Dominican Republic--the Barahona Peninsula. Most of Noel's heaviest rains are still offshore, but these rains will move inland over the island of Hispaniola tonight, and pound the island for at least the next two days. This will result in an extremely dangerous flooding situation in the southern portion of both Haiti and the Dominican Republic, due to the high mountains that will enhance Noel's rains. Long range radar out of Puerto Rico shows heavy rains affecting Puerto Rico and the Dominican Republic, and these rains have already exceeded eight inches over a wide area of ocean to the east of Noel's center (Figure 1). Tonight's weather discussion from the National Weather Service in San Juan, Puerto Rico, called the situation on that island "an increasingly more dangerous and life-threatening event for many areas." Many flash floods and mudslides have been reported on the island, and with at least 24 more hours of flooding rains expected there, the island can expect millions of dollars in flooding damage from Noel.

The flooding situation on Hispaniola will be far worse. Satellite loops show very vigorous thunderstorms reaching high into the atmosphere have developed on the storm's northeast side. These thunderstorms will trigger rains of up to 1-2 inches per hour when they move over Hispaniola Monday. With Noel moving very slowly and expected to bring heavy rains to the island for at least two days, a flooding situation as dangerous as occurred in 2004 with Hurricane Jeanne may result. Jeanne passed just north of Haiti as a tropical depression, dumping about 13 inches of rain over the northern mountains. The resulting floods killed over 3,000 people.

Wind shear has fallen to 10-20 knots this evening, and may continue to fall. This may allow Noel to intensify into a hurricane Monday. However, wind shear is higher the further north Noel gets, and passage over the rugged southern Peninsula of Haiti may prevent the storm from reaching hurricane strength.

Figure 1. Latest precipitation estimate from the Puerto Rico radar.

The latest models runs still do not give us a lot of confidence that we know where Noel will go or how strong it will get. The key feature controlling Noel's path is a trough of low pressure forecast to move off the U.S. East Coast four days from now. If this trough is strong enough, and Noel is large enough and far enough north, the trough will force Noel across Cuba, into the Bahamas, then northeastward out to sea. Exactly where this recurvature will occur is problematic, with the GFDL and HWRF predicting this will occur over the western Bahamas, and the GFS predicting a path close to Miami in the Eastern Bahamas. In either scenario, it is unlikely that Noel would affect South Florida as anything stronger than a Category 1 hurricane, since the storm must get through Cuba first, and deal with higher wind shear to the north of Cuba. If the storm makes a direct hit on South Florida this week, it would likely be as a tropical storm.

The models have been trending more northerly with their solutions, and it now appears unlikely that Noel will make it into the Western Caribbean past the Cayman Islands. The Bahamas, Cuba, Jamaica, the Cayman Islands, South Florida, and Hispaniola are the places that may receive major impacts from Noel.

I'll have an update Monday morning.

Jeff Masters

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.