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Hurricane Willa Discussion Number  11
NWS National Hurricane Center Miami FL       EP242018
300 PM MDT Mon Oct 22 2018

Willa continues to exhibit an impressive presentation in satellite
imagery, however the small eye has become cloud filled this
afternoon and and earlier microwave data indicated that an
eyewall replacement cycle had begun.  Subjective and objective
data T-numbers are a little lower than this morning, and the
initial intensity has been set at 135 kt for this advisory.  The
Air Force Reserve Hurricane Hunter aircraft that was en route to
Willa around midday was struck by lightning in one of the outer rain
bands and had to return to base due to safety issues regarding
some of the onboard equipment.

The hurricane has been moving due northward today at about 7 kt.
The track forecast reasoning remains unchanged from the previous
advisory as Willa is currently moving around the western portion of
a deep-layer ridge.  An approaching shortwave trough should turn
Willa north-northeastward, then northward toward the west-central
coast of Mexico on Tuesday, and the hurricane is forecast to make
landfall within the hurricane warning area between San Blas and
Mazatlan Tuesday afternoon or evening.  There are still some model
differences regarding the timing of landfall, and the NHC track
forecast is near the various consensus aids to account for these
variations in forward speed.

The rapid intensification phase that Willa has gone through since
its formation on Saturday appears to have ended now that an eyewall
replacement has begun.  Although the hurricane is forecast to remain
in a low to moderate wind shear environment and over warm SSTs
through tonight, some weakening is likely due to internal dynamics
of the eyewall replacement.  Increasing southwesterly shear on
Tuesday is likely to cause some additional weakening, and the NHC
intensity forecast has been adjusted accordingly, however, Willa is
forecast to remain a dangerous major hurricane through landfall.
Rapid weakening will occur Tuesday night as Willa moves over the
mountainous terrain of Mexico, and the cyclone is expected to
dissipate on Wednesday.  Moisture from the remnants of Willa are
forecast to spread northeastward over northern Mexico and
portions of Texas where a swath of heavy rainfall is expected
midweek.

Key Messages:

1. A life-threatening storm surge is expected Tuesday along the
coasts of the Isla Marias, and west-central and southwestern
Mexico near the path of Willa.  Residents should rush preparations
to completion to protect life and property and follow any advice
given by local officials.

2. Everyone in Isla Marias, and within the hurricane warning area
along the coast of west-central Mexico should prepare for life-
threatening major hurricane winds associated with the core of
Willa.  Hurricane force winds will also extend inland across the
mountainous areas of west-central Mexico as Willa moves inland.

3. Heavy rainfall from Willa is likely to produce life-threatening
flash flooding and landslides over much of southwestern and
west-central Mexico.


FORECAST POSITIONS AND MAX WINDS

INIT  22/2100Z 19.7N 107.2W  135 KT 155 MPH
 12H  23/0600Z 20.7N 107.1W  125 KT 145 MPH
 24H  23/1800Z 22.0N 106.5W  110 KT 125 MPH
 36H  24/0600Z 23.9N 104.7W   60 KT  70 MPH...INLAND
 48H  24/1800Z 26.2N 101.5W   25 KT  30 MPH...INLAND
 72H  25/1800Z...DISSIPATED

$$
Forecaster Brown

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