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HURRICANE GASTON DISCUSSION NUMBER  29
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL072016
500 PM AST MON AUG 29 2016

Gaston's satellite presentation continues to slowly degrade, with
the latest microwave data suggesting it could be undergoing an
eyewall replacement.  The initial wind speed is lowered to 90 kt in
accordance with the latest satellite estimates.  Little change in
intensity is expected for the next couple of days while Gaston
remains over warm waters with light-to-moderate shear, although the
eyewall cycle adds a wrinkle to the forecast.  In a couple of days,
a gradual increase in shear, along with a decrease in SSTs, should
cause a more significant weakening. Intensity guidance is a bit
lower than 6 hours ago, and the latest NHC intensity forecast
follows that trend.

Gaston appears to be moving a bit faster, now north-northeastward at
3 kt. Due to a ridge becoming established to the southeast of the
cyclone, Gaston should accelerate to the east-northeast over the
next few days.  The end of the forecast is tricky, with some
uncertainties over how Gaston interacts with the mid-latitude
westerlies and the strength of an eastern Atlantic ridge.  While
the overall guidance suite has shifted somewhat to the north at days
4 and 5, the ECMWF has been more consistent during the past few
days and has stayed farther south.  Thus, the new forecast is on
the southern side of the guidance envelope, to the south of the
model consensus at long range.

FORECAST POSITIONS AND MAX WINDS

INIT  29/2100Z 31.2N  55.2W   90 KT 105 MPH
 12H  30/0600Z 31.6N  54.5W   90 KT 105 MPH
 24H  30/1800Z 32.2N  52.8W   85 KT 100 MPH
 36H  31/0600Z 33.2N  50.7W   85 KT 100 MPH
 48H  31/1800Z 34.6N  48.0W   85 KT 100 MPH
 72H  01/1800Z 37.7N  39.6W   75 KT  85 MPH
 96H  02/1800Z 38.5N  32.0W   55 KT  65 MPH
120H  03/1800Z 40.0N  28.0W   40 KT  45 MPH

$$
Forecaster Blake

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