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Gabrielle headed for the Outer Banks of North Carolina

By: Dr. Jeff Masters, 1:18 PM GMT on September 08, 2007

Subtropical Storm Gabrielle formed last night, after a day-long struggle trying to figure out which of two centers to consolidate around. Gabrielle finally decided it would use both centers, and a very large and elongated circulation resulted. This makes Gabrielle a subtropical storm, since the heavy thunderstorm activity is well removed from the center of circulation. Satellite loops show that a long band of heavy thunderstorms to the north of Gabrielle is beginning to wrap into the center of the storm, meaning that Gabrielle is making the transition to a tropical storm. Once heavy thunderstorm activity becomes concentrated around the center, the storm will be able intensify. This intensification will be aided early Sunday morning when Gabrielle passes over the warmest waters of the Gulf Stream, about 100 miles off the coast of North Carolina. Wind shear is about 10 knots over Gabrielle, which should also aid in intensification. My estimate is that intensification will begin late this afternoon. Gabrielle will probably have time to intensify to a 55-60 mph tropical storm before landfall (or a close miss) along the Outer Banks of North Carolina.

This morning's QuikSCAT pass mostly missed Gabrielle, but did note winds up to 30 knots (35 mph) along the storm's west side. The Hurricane Hunters are not due back in Gabrielle until 2pm EDT this afternoon. The NOAA jet is scheduled to fly tonight. The storm's outer rain band is now visible on Morehead City long-range radar.

Recent model runs have been pushing the track of Gabrielle further and further out to sea, and there is a good chance the storm will miss making a direct hit on the U.S. Regardless, most of the North Carolina coast from Wilmington to Kill Devil Hills will experience heavy rain of 1-4 inches. Tropical storm-force winds and a 3-4 foot storm surge will also affect some areas. Gabrielle is currently (Figure 1) producing rainfall amounts of about one inch every three hours along its northern band (Figure 1). These rainfall amounts should increase by about 50% by tomorrow as the storm grows more tropical in nature. Unfortunately, Gabrielle's rains will not penetrate very far inland to help alleviate the North Carolina drought. It now appears that Gabrielle will not affect New England, but could bring tropical storm force winds to Newfoundland early next week as an extratropical storm.

Figure 1. Estimates of rainfall over a 3-hour period ending at 8pm EDT last night. Note the higher rainfall rates present in the tropical disturbance just south of the Cape Verdes Islands. Tropical systems produce more rain than subtropical storms. Image credit: NASA.

I'll have a new blog later today if there's a significant change to Gabrielle. Otherwise, I'll post by Sunday morning at 10am. There is a tropical wave off the coast of Africa that may develop to talk about.

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.

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