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Tropical Storm GASTON Forecast Discussion


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000
WTNT42 KNHC 250233
TCDAT2

TROPICAL STORM GASTON DISCUSSION NUMBER  10
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL072016
1100 PM AST WED AUG 24 2016

Satellite intensity estimates from all agencies, recent ASCAT
measurements, and numerous dropsondes from the unmanned NASA
Global Hawk aircraft indicate that the initial intensity of Gaston
remains at 60 kt. Strong upper-level westerlies blowing around the
base of an upper low to the northwest of Gaston are already
affecting the symmetry of the cyclone, and the low-level center is
on the western edge of the convection. This strong westerly shear is
expected to last for about 36 hours, resulting in some weakening.
Most of the global models move the upper low toward the southwest,
and in about 2 days, Gaston will again be in a favorable environment
for intensification.  On this basin, the NHC forecast weakens the
cyclone during the next 24 to 36 hours, and then calls for Gaston to
intensify and reach hurricane strength over the warm waters of the
central Atlantic. The forecast follows closely the SHIPS model and
the intensity consensus.

Gaston is moving toward the northwest or 310 degrees at 15 kt
steered by the flow between the subtropical high and the same
low that is causing the shear. As the low moves southwestward and
the ridge to the north of the cyclone amplifies, Gaston should turn
a little more toward the west-northwest with a decrease in forward
speed. The NHC forecast is the middle of the guidance envelope and
is basically on top of the latest multi-model consensus. No
significant changes were made to the previous track forecast.


FORECAST POSITIONS AND MAX WINDS

INIT  25/0300Z 18.6N  42.1W   60 KT  70 MPH
 12H  25/1200Z 20.1N  44.0W   60 KT  70 MPH
 24H  26/0000Z 22.3N  46.0W   50 KT  60 MPH
 36H  26/1200Z 24.5N  48.3W   45 KT  50 MPH
 48H  27/0000Z 26.3N  51.0W   55 KT  65 MPH
 72H  28/0000Z 28.5N  55.5W   70 KT  80 MPH
 96H  29/0000Z 30.5N  58.5W   80 KT  90 MPH
120H  30/0000Z 32.0N  59.5W   85 KT 100 MPH

$$
Forecaster Avila