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Hurricane Willa Discussion Number   8
NWS National Hurricane Center Miami FL       EP242018
900 PM MDT Sun Oct 21 2018

Willa has continued to rapidly intensify this evening.  Satellite
images show a well-defined circular eye with a surrounding ring of
cold cloud tops that are near -80 deg C over the southeastern
quadrant.  The initial intensity is set to 125 kt, which is near the
latest Dvorak ADT estimates from CIMSS at the University of
Wisconsin.  Willa has strengthened at an incredible rate since
genesis, intensifying from a tropical depression to a category 4
hurricane in less than 48 hours.

Willa is gradually turning toward the right, with the initial motion
estimated to be 340/6 kt.  The hurricane is expected to turn
northward on Monday as it moves around the western periphery of a
mid-level ridge to the east, followed by a faster northeastward
motion Monday night and Tuesday when a shortwave trough approaches
the system.  The models are in fairly good agreement, and only small
changes were made to the previous NHC track forecast.  On the
forecast track, Willa is expected to move over Las Islas Marias on
Tuesday and then move inland over southwestern and west-central
Mexico Tuesday night or early Wednesday.

The hurricane has certainty taken advantage of the near ideal
environmental conditions and since these conditions will persist a
little longer, some additional strengthening is shown in the short
term.  However, some fluctuations in intensity could occur due to
eyewall replacement cycles.  The models then show a gradual increase
in shear and a decrease in available moisture around 24 hours, and
these factors should cause a slow weakening trend. Regardless,
Willa is forecast to remain a dangerous hurricane, bringing multiple
life-threatening hazards to the coast of Mexico. Rapid weakening is
forecast after the system moves inland and interacts with the
mountainous terrain.  The NHC intensity forecast lies near the high
end of the model guidance through dissipation.

Key Messages:

1. Willa is forecast to be a dangerous hurricane when it reaches the
Islas Marias and the coast of southwestern Mexico by late Tuesday or
Wednesday bringing a life-threatening storm surge and flash flooding
along with damaging hurricane-force winds. A Hurricane Warning is
in effect for these areas, and residents should rush preparations to
completion to protect life and property and follow any advice given
by local officials.


FORECAST POSITIONS AND MAX WINDS

INIT  22/0300Z 17.7N 107.2W  125 KT 145 MPH
 12H  22/1200Z 18.6N 107.4W  135 KT 155 MPH
 24H  23/0000Z 19.7N 107.5W  125 KT 145 MPH
 36H  23/1200Z 20.7N 107.2W  115 KT 130 MPH
 48H  24/0000Z 22.1N 106.2W  100 KT 115 MPH
 72H  25/0000Z 26.2N 101.3W   30 KT  35 MPH...POST-TROP/INLAND
 96H  26/0000Z...DISSIPATED

$$
Forecaster Cangialosi

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