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Hurricane WILLA


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Hurricane Willa Discussion Number   6
NWS National Hurricane Center Miami FL       EP242018
900 AM MDT Sun Oct 21 2018

First-light GOES-16 visible satellite imagery shows that Willa
continues to become better organized, with a tightly coiled band
of convection wrapping around the center.  There has also been
evidence of a small eye in recent microwave and infrared satellite
pictures.  Subjective and objective satellite intensity estimates
range from 77 kt to 90 kt, and the initial intensity has been
increased to 85 kt for this advisory.

Willa is moving northwestward or 325/6 kt. The track guidance
continues to indicate that Willa will move northwestward today,
then turn northward on Monday, and then head north-northeastward
on Tuesday between a deep-layer ridge that extends westward from the
Gulf of Mexico and an approaching mid-level trough. The dynamical
model guidance remains in good overall agreement on this scenario,
but there are differences in how quickly Willa will accelerate
north-northeastward.  The UKMET and ECMWF are much slower than the
remainder of the dynamical models, with the GFS and GFS ensemble
mean the fastest.  The NHC track forecast brings the center of the
Willa onshore of the coast of southwestern Mexico within 72 h, and
it lies closest to the HFIP corrected consensus, which is a little
faster than the other consensus aids.

The hurricane is expected to remain within low vertical wind shear
and over warm waters of around 28 degrees Celsius during the next
day or two.  These very favorable conditions are expected to allow
steady to rapid strengthening through Monday night, and the NHC
forecast is near the upper end of the intensity guidance.  By 48
hours, increasing southwesterly shear is forecast to initiate
weakening, but Willa is likely to remain a very strong hurricane
through landfall in southwestern Mexico.  After landfall, rapid
weakening and dissipation over the mountainous terrain of mainland
Mexico should occur.

Key Messages:

1. Willa is forecast to be a hurricane when it reaches the coast of
southwestern mainland Mexico by late Tuesday or Wednesday bringing a
life-threatening storm surge, dangerous winds, and life-threatening
flash flooding, and hurricane and tropical storm watches are now
in effect for a portion of the area.  Residents in the watch areas
should monitor the progress of this system and follow any advice
given by local officials.


FORECAST POSITIONS AND MAX WINDS

INIT  21/1500Z 16.6N 106.7W   85 KT 100 MPH
 12H  22/0000Z 17.2N 107.2W   95 KT 110 MPH
 24H  22/1200Z 18.2N 107.6W  110 KT 125 MPH
 36H  23/0000Z 19.3N 107.7W  120 KT 140 MPH
 48H  23/1200Z 20.4N 107.5W  110 KT 125 MPH
 72H  24/1200Z 23.3N 105.5W   80 KT  90 MPH...INLAND
 96H  25/1200Z 26.5N 101.0W   20 KT  25 MPH...POST-TROP/INLAND
120H  26/1200Z...DISSIPATED

$$
Forecaster Brown

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