Hurricane GONZALO

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HURRICANE GONZALO DISCUSSION NUMBER  27
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL082014
1100 PM AST SAT OCT 18 2014


Gonzalo has been maintaining a central dense overcast feature over
the large eye feature noted in microwave satellite imagery since the
previous advisory. A 19/0116 UTC ASCAT-B high-resolution overpass
indicated 78-80 kt surface winds in the eastern quadrant about 45
nmi southeast of the center, so the intensity remains 80 kt for
this advisory, which could be a conservative estimate. The same
ASCAT pass also indicted that the wind field in the southeastern
semicircle had expanded significantly, and the respective wind radii
have been increased accordingly.

Gonzalo continues to accelerate toward the northeast and the
initial motion estimate is 040/34 kt. The latest 0000 UTC model
guidance remains tightly packed, so no significant changes were
made to the previous forecast track. Gonzalo should continue to move
northeastward and then east-northeastward in the flow between a
deep-layer trough to the west of the hurricane and a subtropical
ridge to its south. The NHC forecast track is just an update of the
previous advisory track, and lies close to the consensus model TVCA.
The post-tropical portion of the forecast track was coordinated with
the NOAA Ocean Prediction Center.

Recent SST analyses and the forecast motion indicate that Gonzalo
should continue to move over a thermal ridge for a few more hours,
which should help the cyclone maintain status as a tropical
cyclone. By 12 hours, however, SSTs less than 12C and increasing
southwesterly vertical wind shear of more than 30 kt should result
in Gonzalo making the transition to a strong post-tropical
extratropical cyclone.  Gradual weakening is forecast after the
transition occurs and to continue until dissipation occurs in by 72
hours. The NHC intensity forecast follows the Decay-SHIPS model
through 12 hours, and then is based on input from the Ocean
Prediction Center.

FORECAST POSITIONS AND MAX WINDS

INIT  19/0300Z 42.3N  57.0W   80 KT  90 MPH
 12H  19/1200Z 47.0N  50.5W   70 KT  80 MPH...POST-TROP/EXTRATROP
 24H  20/0000Z 52.0N  38.5W   60 KT  70 MPH...POST-TROP/EXTRATROP
 36H  20/1200Z 54.0N  24.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
 48H  21/0000Z 57.0N   8.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
 72H  22/0000Z...DISSIPATED

$$
Forecaster Stewart

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