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HURRICANE GASTON DISCUSSION NUMBER  38
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL072016
1100 PM AST WED AUG 31 2016

Gaston's infrared satellite pattern has changed little since the
previous advisory.  The eye remains ragged but clear, and cold
convective tops continue in all quadrants.  Recent microwave
imagery, however, does show that the southwestern eyewall is now
open, and there are some indications that the circulation is
becoming tilted due to west-southwesterly shear.  Still, the
initial intensity remains 90 kt based on a blend of final-T and CI
numbers from TAFB and SAB, which is also supported by the latest CI
estimate from the objective ADT.

The hurricane is expected to be over sea surface temperatures
warmer than 26C for another 12-18 hours while vertical shear is
forecast to be at or above 20 kt for the next few days.  Therefore,
a gradual weakening trend is anticipated, and Gaston is forecast to
lose hurricane intensity in about 36 hours while it approaches the
western Azores.  After that time, continued weakening is expected,
and Gaston is likely to become a remnant low in about 72 hours
after it has passed the Azores and loses its deep convection over
very cold water.  Dissipation is still expected by day 4.  The
intensity models are in very good agreement on the weakening trend,
and the updated NHC forecast is close to the intensity consensus.

The initial motion remains northeastward but a little faster at
055/17 kt.  Gaston is embedded in the mid-latitude westerlies, and
it is expected to turn east-northeastward and accelerate during the
next 24 hours.  After that time, Gaston could slow down a bit while
it moves across the Azores, and then turn back toward the northeast
when it becomes a remnant low.  Like the intensity guidance, the
track models are in very good agreement, and no significant changes
were needed from the previous forecast.

FORECAST POSITIONS AND MAX WINDS

INIT  01/0300Z 36.0N  45.4W   90 KT 105 MPH
 12H  01/1200Z 37.2N  42.1W   80 KT  90 MPH
 24H  02/0000Z 38.2N  37.5W   70 KT  80 MPH
 36H  02/1200Z 38.7N  33.3W   60 KT  70 MPH
 48H  03/0000Z 39.2N  30.3W   45 KT  50 MPH
 72H  04/0000Z 42.1N  24.9W   30 KT  35 MPH...POST-TROP/REMNT LOW
 96H  05/0000Z...DISSIPATED

$$
Forecaster Berg

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