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HURRICANE GASTON DISCUSSION NUMBER  26
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL072016
1100 PM AST SUN AUG 28 2016

Gaston remains a well organized hurricane. Satellite images indicate
that the eye remains quite distinct with a symmetric ring of deep
convection around it.  The upper-level outflow is well established
both to the west and the east of the system.  The latest Dvorak
classifications from TAFB and SAB are 5.5/102 kt, and automated
values from CIMSS at the University of Wisconsin are 5.9/112 kt.
Based on these data, the initial wind speed is nudged upward to 105
kt.

Gaston has not moved very little during the last several hours. A
continued slow and likely erratic northward motion is forecast
overnight and Monday while Gaston remains in weak steering currents
caused by a blocking mid-level ridge to its northwest.  A trough
that is currently over eastern Canada is expected to dampen by the
time it nears Gaston, but it should be strong enough to erode the
ridge and allow the hurricane to become embedded in the mid-latitude
westerlies. This pattern change should result in Gaston's turning
east-northeastward in about 24 hours, with the cyclone continuing in
that direction through the remainder of the forecast period.  The
model guidance remains tightly packed, and little change was made to
the previous NHC track prediction.

The atmospheric conditions suggest that Gaston could maintain its
strength for the next day or so, however, given the expected slow
motion of the cyclone there is some chance that cold water upwelling
would counteract that.  Beyond that time, the hurricane is
likely to encounter an environment of increasing shear, drier air,
and cooler water. Given these expected conditions, the NHC intensity
forecast shows a gradual weakening trend beginning on Monday.  This
prediction is in best agreement with the SHIPS guidance.

FORECAST POSITIONS AND MAX WINDS

INIT  29/0300Z 30.6N  55.2W  105 KT 120 MPH
 12H  29/1200Z 30.9N  55.4W  105 KT 120 MPH
 24H  30/0000Z 31.4N  54.9W  100 KT 115 MPH
 36H  30/1200Z 32.1N  53.5W   95 KT 110 MPH
 48H  31/0000Z 33.0N  51.5W   95 KT 110 MPH
 72H  01/0000Z 35.5N  46.0W   90 KT 105 MPH
 96H  02/0000Z 37.4N  38.7W   75 KT  85 MPH
120H  03/0000Z 37.7N  33.0W   60 KT  70 MPH

$$
Forecaster Cangialosi

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