Hurricane GONZALO

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HURRICANE GONZALO DISCUSSION NUMBER   9
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL082014
1100 AM AST TUE OCT 14 2014

Data from an Air Force Reserve Hurricane Hunter aircraft and the San
Juan Doppler weather radar indicate that the earlier intensification
process has abated, which is apparently due to some shear-induced
disruption of the eye. Maximum 700 mb flight-level winds observed
thus far are 112 kt and maximum SFMR winds through most of the
morning have been around 93 kt. The central pressure has also
leveled off during the past few hours at around 973 mb. A blend of
the flight-level surface-wind conversion and SFMR winds support
maintaining an intensity of 95 kt.

Gonzalo continues to move northwestward with a motion of 315/11 kt.
There is no significant change to the previous forecast track or
reasoning. The NHC model guidance is in excellent agreement on the
hurricane continuing to move northwestward around the southwestern
for periphery of a deep-layer ridge the during the next 36 hours.
After that, the western portion of the ridge is expected to weaken
as a strong mid-latitude trough and associated cold front currently
located over the southeastern U.S. moves eastward across the Bahamas
by 48 hours. The increasing southwesterly flow ahead of those
systems should gradually accelerate Gonzalo toward the northeast,
with the cyclone potentially threatening Bermuda in about three
days' time. Gonzalo is expected to merge with the strong cold front
or become extratropical by 120 hours. The new track forecast is
similar to the previous advisory track, and lies close to a blend of
the GFEX and TVCA consensus models.

Recent radar and satellite data indicate that the eye of Gonzalo has
been clearing out and gradually becoming better defined with a
diameter of about 20 nmi. Once the eyewall stabilizes again,
intensification will likely resume, and in fact the reconnaissance
aircraft a few moments ago observed an SFMR wind of 99 kt that
suggests this intensification is beginning.  Buoy data indicate that
water temperatures are slightly cooler than what the SHIPS model is
indicating, probably due to cold upwelling created by the wake of
former Hurricane Fay, but they are still sufficiently warm enough to
support a category 4 hurricane. The best vertical shear conditions
and upper-level outflow regime are expected to occur on Wednesday
and into Thursday morning, and that is when Gonzalo is expected to
strengthen into a category 4 hurricane.  Afterwards, eyewall cycles
and possible cold upwelling beneath the hurricane are likely to
cause some fluctuations in the intensity. By 72 hours, increasing
southwesterly wind shear ahead of the aforementioned deep trough and
strong cold front is expected to induce weakening. By 120 hours,
Gonzalo should be over cold waters of the North Atlantic and
experiencing vertical shear of more than 50 kt, which should result
in the cyclone becoming a extratropical low. The NHC intensity
forecast is similar to the previous advisory and is above all of the
available intensity guidance.

FORECAST POSITIONS AND MAX WINDS

INIT  14/1500Z 20.3N  65.2W   95 KT 110 MPH
 12H  15/0000Z 21.7N  66.4W  100 KT 115 MPH
 24H  15/1200Z 23.3N  67.8W  110 KT 125 MPH
 36H  16/0000Z 24.6N  68.6W  120 KT 140 MPH
 48H  16/1200Z 26.1N  68.6W  115 KT 130 MPH
 72H  17/1200Z 30.4N  66.5W  105 KT 120 MPH
 96H  18/1200Z 37.4N  62.6W   90 KT 105 MPH
120H  19/1200Z 46.8N  53.8W   70 KT  80 MPH...POST-TROP/EXTRATROP

$$
Forecaster Stewart

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