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Hurricane GONZALO


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HURRICANE GONZALO DISCUSSION NUMBER  11
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL082014
1100 PM AST TUE OCT 14 2014

Data from an Air Force Hurricane Hunter reconnaissance aircraft
indicate that Gonzalo has continued to strengthen.  The plane
reported maximum flight-level of 125 kt in the northeastern
quadrant and peak SFMR winds of 108 kt. The minimum surface pressure
also has fallen about 17 mb during the last 9 hours to 954 mb.
Satellite images show that the eye has warmed and shrunk to a
diameter of 8 n mi while the inner core has generally become better
defined. However, Gonzalo has been maintaining an asymmetric
distribution of convection, presumably due to around 15 kt of
south-southwesterly shear of affecting the cyclone according to the
latest SHIPS and UW-CIMSS shear analyses. A blend of the flight-
level and SFMR wind data is used to raise the initial intensity of
110 kt.

Water vapor imagery and cloud-tracked wind vectors show an upper-
level trough between Bermuda and the southeastern U.S. responsible
for the south-southwesterly shear over Gonzalo, but the shear should
not be enough to prevent additional intensification from taking
place over warm waters of 28-29 deg C during the next day or so.
At some point during this time, fluctuations in strength due to
difficult-to-forecast inner core evolution are probable. By 72
hours, a significant increase in south-southwesterly shear should
induce a considerable weakening trend. Increasing baroclinicity in
the near-storm environment, much cooler waters, and drier and more
stable air wrapping around the hurricane's circulation should result
in extratropical transition by day 4. The NHC intensity forecast is
about the same as the previous one, and is near or higher than the
highest intensity guidance (SHIPS/LGEM) through 36 hours but close
to the multi-model consensus after that.

Gonzalo has continued to move on a northwestward course, or 320/11,
though the center has wobbled a bit toward the left during the
last couple of hours.  The hurricane should gradually turn north-
northwestward and then northward and slow down as it moves around
the western periphery of an eastward-shifting central Atlantic ridge
during the next 24 to 36 hours.  By 48 hours, Gonzalo should
encounter a deep-layer south-southwesterly flow associated with a
potent mid-latitude trough swinging out of the east-central United
States. This flow pattern should turn Gonzalo north-northeastward
with increasing forward speed.  Although the track guidance is
tightly clustered through 72 hours, there is still some along-track
spread in the model solutions, with the ECMWF depicting a weaker and
much-slower-moving cyclone.  The new NHC forecast places less weight
on the ECMWF, owing to Gonzalo's current intensity. The official NHC
forecast lies on the far eastern side of the guidance envelope and
to the right of the multi-model consensus.


FORECAST POSITIONS AND MAX WINDS

INIT  15/0300Z 22.2N  66.6W  110 KT 125 MPH
 12H  15/1200Z 23.4N  67.6W  120 KT 140 MPH
 24H  16/0000Z 24.9N  68.5W  120 KT 140 MPH
 36H  16/1200Z 26.3N  68.7W  115 KT 130 MPH
 48H  17/0000Z 28.5N  67.7W  110 KT 125 MPH
 72H  18/0000Z 34.7N  64.1W  100 KT 115 MPH
 96H  19/0000Z 45.1N  56.7W   80 KT  90 MPH...POST-TROP/EXTRATROP
120H  20/0000Z 52.5N  42.0W   65 KT  75 MPH...POST-TROP/EXTRATROP

$$
Forecaster Kimberlain

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