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000
WTPZ41 KNHC 310234
TCDEP1

TROPICAL STORM VANCE DISCUSSION NUMBER 4
NWS NATIONAL HURRICANE CENTER MIAMI FL EP212014
800 PM PDT THU OCT 30 2014

Vance has strengthened a little this evening. Infrared satellite images indicate that deep convection has increased slightly to the northeast of the center and in a band on the south and east sides of the circulation. A blend of the latest Dvorak intensity estimates from TAFB, SAB, and the University of Wisconsin-CIMSS supports raising the initial wind speed to 40 kt. Southerly to southwesterly shear and dry air in the low- to mid-levels of the atmosphere are currently affecting Vance, and these conditions are expected to persist for about another day. Therefore, only slow strengthening is predicted during that time. Over the weekend, however, the atmosphere is expected to moisten near the storm while the shear lessens, providing a better opportunity for more significant strengthening. By the end of the forecast period, the global models show a sharp increase in southwesterly shear, which should cause the cyclone to begin weakening. The NHC intensity forecast lies between the SHIPS model and the intensity model consensus.

The storm has been moving slowly west-southwestward during the past 6 to 12 hours. A mid-level ridge located to the north and northwest of Vance is expected to steer the cyclone west-southwestward to westward during the next day or two. After that time, a gradual turn to the north and then northeast is forecast as the ridge weakens and shifts eastward in response to an approaching large trough. Although the models are in agreement in the large-scale steering pattern, there is a fair amount of spread in where Vance turns northward. The NHC track forecast has been adjusted a little to the left of the previous one for the first 72 hours to be in better agreement with the latest guidance.

FORECAST POSITIONS AND MAX WINDS

INIT 31/0300Z 10.8N 101.3W 40 KT 45 MPH 12H 31/1200Z 10.4N 102.0W 45 KT 50 MPH 24H 01/0000Z 10.0N 103.3W 50 KT 60 MPH 36H 01/1200Z 9.9N 105.1W 50 KT 60 MPH 48H 02/0000Z 10.4N 107.0W 55 KT 65 MPH 72H 03/0000Z 12.9N 110.2W 70 KT 80 MPH 96H 04/0000Z 17.1N 110.4W 65 KT 75 MPH 120H 05/0000Z 20.5N 107.5W 45 KT 50 MPH

$$ Forecaster Cangialosi



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