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97L a heavy rain threat to the Lesser Antilles and Puerto Rico today

By: Dr. Jeff Masters, 2:51 PM GMT on October 03, 2010

A large region of disturbed weather (Invest 97L), centered about 200 miles east of the northern Lesser Antilles Islands, is headed west to west-northwest at about 10 mph and will bring heavy rain showers and gusty winds to the northern Lesser Antilles Islands, Puerto Rico, and the Virgin Islands today through Tuesday. These showers can be seen on Martinique radar this morning, and have increased considerably since yesterday, thanks to the presence of an upper level trough of low pressure making the atmosphere more unstable. This same trough is also bringing high wind shear of 20 -25 knots, though, so development of 97L is not expected today. Recent satellite imagery shows a large area of intense thunderstorms associated with 97L, but the activity is not well organized. The SHIPS model predicts that wind shear over 97L will fall to the moderate range, 10 - 20 knots, Monday through Thursday. The ECMWF model continues to be the only model showing significant development 97L in the next seven days. The model predicts 97L will be near Puerto Rico on Monday, the Dominican Republic on Tuesday, and Haiti on Wednesday, with the storm developing into a tropical depression on Thursday just north of Haiti, then moving northwards through the Turks and Caicos Islands and out to sea on Thursday. NHC is giving 97L a 10% chance of developing into a tropical depression by Tuesday, and has not tasked the Hurricane Hunters to fly into the storm over the next two days. 97L will move at about 10 mph through the islands today through Wednesday, bringing the potential for an extended 3-day period of heavy rains for the islands in its path. These rains may result in life-threatening flash flooding and mudslides in Puerto Rico and the Dominican Republic beginning on Monday, and for Haiti beginning on Tuesday. Flash flood watches are posted for the Virgin Islands and Puerto Rico today.

Figure 1. Morning satellite image of Invest 97L.

Flood waters receding in northeastern North Carolina
Flood waters are receding in northeastern North Carolina, where the Cashie River in Windsor caused major flooding that put many homes under five feet of water. North Carolina was deluged by more than twenty inches of rain in some regions over the past week, due to tropical moisture streaming northwards in advance of Tropical Storm Nicole. Representatives from Portlight.org are surveying the hardest-hit areas of North Carolina to begin identifying needs in the wake of the flooding. Portlight expects to perform the first deployment of their new relief trailer within the next few days and send a truck loaded with water, food and personal hygiene supplies. You can follow their progress via the Portlight.org blog.

Our new Weather Extreme blogger, Christopher C. Burt, has posted a comparison of the maximum rainfall totals in each state affected by Hurricane Floyd of 1999, and this weeks extreme rainfall event, which he dubs "Super-Rainstorm Nicole." The two storms were very similar in the amount of rain they dumped, and we are very fortunate that moderate drought conditions preceded the arrival of this week's storm, or else billions in damage would have resulted.

Figure 2. Rainfall for the 7-day period ending at 8am EDT this morning shows the remarkable accumulations that fell in association with the tropical moisture ahead of Tropical Storm Nicole. Image credit: NOAA.

Elsewhere in the tropics
An area of disturbed weather near 9N, 44W is fairly close to having a closed circulation, as seen on a 8:04am EDT pass by the ASCAT satellite. However, satellite imagery shows only a limited amount of heavy thunderstorms, and there is plenty of dry air in the vicinity that is interfering with development. The disturbance is headed to the northwest, and the computer models predict the disturbance will not affect any land areas for at least the next seven days. NHC is giving the disturbance a 10% chance of developing into a tropical depression by Tuesday.

Next update
I'll have an update Monday morning.

Jeff Masters
Saving a few...
Saving a few...
items by placing them on the roof. Vanceboro, NC


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