Hurricane GONZALO

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HURRICANE GONZALO DISCUSSION NUMBER  25
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL082014
1100 AM AST SAT OCT 18 2014

Gonzalo's convective canopy is becoming ragged and substantially
asymmetric with the cold clouds primarily seen in the northern
semicircle.  Subjective Dvorak and the objective Advanced Dvorak
Technique suggest a range from 65 to 77 kt for the maximum sustained
winds, while the CIMSS Advanced Microwave Sounding Unit estimate
indicates about 85 kt.  A blend of these gives 80 kt for the initial
intensity, a considerable drop from the previous advisory.  As
Gonzalo will be moving north of the warm Gulf Stream waters and
experiencing increasingly hostile vertical wind shear over the next
day, the hurricane should steadily weaken. In about a day,
extratropical transition should occur, consistent with the FSU
Cyclone Phase Space and SHIPS diagnostic analyses. However, rather
than getting a baroclinic kick after ET, Gonzalo is anticipated by
the global model guidance to continue weakening until dissipation in
about three days.  The NHC intensity forecast is based upon the IVCN
multi-model intensity consensus while a tropical cyclone and upon
the GFS and ECMWF global models while the system is extratropical.

Gonzalo is moving toward the north-northeast at 22 kt, as it is
being advected along in the south-southwesterlies north of the
subtropical ridge.  The system should accelerate as it gets picked
up by the core of the jet stream and becomes extratropical.  The
NHC track forecast is based upon the tightly clustered TVCN
multi-model consensus and is just slightly westward of the
previous advisory.

The initial tropical storm and hurricane-force wind radii were
analyzed to be larger than previously indicated based on a
0922Z AMSU pass, as indicated by the CIRA size analyses.

The post-tropical portion of the forecast has been coordinated with
the NOAA Ocean Prediction Center.

FORECAST POSITIONS AND MAX WINDS

INIT  18/1500Z 36.8N  61.7W   80 KT  90 MPH
 12H  19/0000Z 40.8N  58.3W   70 KT  80 MPH
 24H  19/1200Z 47.0N  50.5W   60 KT  70 MPH...POST-TROP/EXTRATROP
 36H  20/0000Z 51.3N  38.7W   55 KT  65 MPH...POST-TROP/EXTRATROP
 48H  20/1200Z 53.5N  23.5W   45 KT  50 MPH...POST-TROP/EXTRATROP
 72H  21/1200Z...DISSIPATED

$$
Forecaster Landsea

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