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HURRICANE GASTON DISCUSSION NUMBER  31
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL072016
500 AM AST TUE AUG 30 2016

Gaston is completing an eyewall replacement cycle and currently
features a well-defined 35 n mi wide eye.  The convective clouds
have eroded somewhat west of the eye since the last advisory, and
the various subjective and objective intensity estimates have also
decreased.  The initial intensity is thus lowered to 85 kt.

The initial motion is now 055/5.  A mid- to upper-level trough
currently seen in water vapor images near Atlantic Canada is
expected to approach Gaston during the next 12 to 24 hours, and that
should cause the hurricane to become embedded in the mid-latitude
westerlies.  As a result, Gaston should accelerate generally
east-northeastward through 72 hours.  At 96 hours, a building ridge
southwest of Gaston may cause a more easterly motion as the cyclone
approaches the Azores Islands.  This should be followed by a
northeastward turn by 120 hours as a second mid-latitude trough
approaches the tropical cyclone.  The track guidance generally
agrees with this scenario, although the model spread increases
after 72 hours.  The new forecast track is changed little from the
previous track and lies near the center of the guidance envelope.

The intensity guidance suggests that little change in strength is
likely for the next 36-48 hours as Gaston moves over relatively
warm water in a light or moderate westerly shear environment.
After that time, increasing shear and decreasing sea surface
temperatures should cause a steady decay.  The new intensity
forecast is an update of the previous forecast in best agreement
with the SHIPS and LGEM models.


FORECAST POSITIONS AND MAX WINDS

INIT  30/0900Z 32.0N  54.0W   85 KT 100 MPH
 12H  30/1800Z 32.4N  52.7W   85 KT 100 MPH
 24H  31/0600Z 33.4N  50.6W   85 KT 100 MPH
 36H  31/1800Z 35.0N  47.7W   85 KT 100 MPH
 48H  01/0600Z 36.8N  43.5W   85 KT 100 MPH
 72H  02/0600Z 39.5N  34.0W   70 KT  80 MPH
 96H  03/0600Z 39.5N  28.5W   50 KT  60 MPH
120H  04/0600Z 42.5N  23.5W   35 KT  40 MPH

$$
Forecaster Beven

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