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Hurricane Willa Discussion Number   7
NWS National Hurricane Center Miami FL       EP242018
300 PM MDT Sun Oct 21 2018

Willa has continued to rapidly strengthen with the eye becoming
very distinct in both visible and infrared satellite imagery.
The surrounding convective tops warmed around mid-day but have
cooled since that time and subjective Dvorak intensity estimates
were 102 and 90 kt, from SAB and TAFB respectively at 18Z.  With
the continued increase in organization since that time, the initial
intensity is set near the upper end of the estimates or 100 kt.

Willa continues moving slowly north-northwestward or 330/5 kt.
There has been no change to the track forecast philosophy over the
past few advisories.  The hurricane is expected to turn northward
tonight or Monday around the western portion of a deep-layer ridge
that extends westward from the Gulf of Mexico over mainland Mexico.
A mid-level trough that is forecast to approach the Baja California
peninsula Monday night and Tuesday should cause Willa to turn north-
northeastward and recurve around the northwestern portion of the
aforementioned ridge.  There are still some differences in how
quickly Willa will recurve, but there is little cross-track spread
in the guidance.  This increases the overall confidence in the NHC
track forecast, which calls for the hurricane to make landfall along
the southwestern coast of Mexico late Tuesday or early Wednesday.

The low shear and warm ocean environment ahead of Willa is expected
to remain quite favorable for strengthening for at least another 12
to 24 hours, and additional intensification is likely tonight and
early Monday.  The new NHC track intensity forecast is above all
the intensity guidance through 36 hours, and now calls for a peak
intensity of 130 kt within that time period.  After that time,
eyewall replacement cycles could result in some fluctuations in
intensity.  Increasing southwesterly shear on Tuesday could result
in some weakening, but Willa is expected to approach the coast of
Mexico as a very dangerous hurricane.  After landfall, rapid
weakening and dissipation over the mountainous terrain of mainland
Mexico should occur.  A 96-hour forecast point is shown for
continuity but the system is likely to dissipate before that time.


Key Messages:

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


FORECAST POSITIONS AND MAX WINDS

INIT  21/2100Z 17.0N 107.0W  100 KT 115 MPH
 12H  22/0600Z 17.8N 107.4W  120 KT 140 MPH
 24H  22/1800Z 18.8N 107.6W  130 KT 150 MPH
 36H  23/0600Z 19.8N 107.6W  125 KT 145 MPH
 48H  23/1800Z 21.0N 107.1W  110 KT 125 MPH
 72H  24/1800Z 24.8N 103.3W   45 KT  50 MPH...INLAND
 96H  25/1800Z 26.8N 100.0W   20 KT  25 MPH...POST-TROP/INLAND
120H  26/1800Z...DISSIPATED

$$
Forecaster Brown

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