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Hurricane WILLA


Hurricane Willa Discussion Number   5
NWS National Hurricane Center Miami FL       EP242018
300 AM MDT Sun Oct 21 2018

Willa has continued to rapidly intensify based on a well-defined CDO
with an intermittent pinhole eye evident in high-resolution GOES-16
infrared (IR) satellite imagery. Upper-level outflow has become well
established in all quadrants. The intensity is difficult to
ascertain since satellite intensity estimates vary widely based on
the scene type used and also the small size of the hurricane. TAFB
and SAB both provided an estimate of T4.0/65 kt, whereas UW-CIMSS
ADT and SATCON were 67 kt and 56 kt, respectively. In contrast, NHC
objective T-numbers are T5.0/90 kt using an embedded center and as
high as T6.0/115 kt using a pinhole eye. Given that the eye has not
been maintained in IR imagery, the advisory intensity of 75 kt lies
between the subjective TAFB/SAB estimate and lower NHC objective

Willa is moving at 315/06 kt. There is no significant change to the
previous forecast track reasoning. Willa is forecast to continue
moving northwestward for the next 24 h or so, followed by a turn
toward the north on Monday, with a motion toward the northeast
expected on Tuesday as the hurricane gradually rounds the western
periphery of the deep-layer ridge. By late Tuesday, Willa is
forecast to accelerate northeastward ahead of a deep-layer trough
that will be approaching Baja California, resulting in landfall
along the west-central coast of Mexico on Wednesday. The latest 00Z
model guidance is tightly packed about the previous forecast track,
and only minor forward speed adjustments were required. A 96-h
position has been provided only for continuity purposes, and Willa
will likely have dissipated over the Mexican mountains by then.

Willa's small inner-core wind field along with ideal environmental
conditions consisting of low shear, high mid-level moisture, and
warm SSTs of 28 deg C should allow the hurricane to continue to
rapidly intensify for the next 24-36 hours, followed by a leveling
off in the intensity by early Tuesday due to expected cold upwelling
beneath the slow-moving hurricane.  In 60-72 hours, increasing
southwesterly shear ahead of the aforementioned deep-layer trough is
expected to induce steady weakening until landfall occurs. Rapid
dissipation over the mountainous terrain of mainland Mexico will
occur after landfall. The official intensity forecast is a tad
above the consensus models HCCA and FSSE, and is little below the
robust Navy COAMPS-TC model forecast.


INIT  21/0900Z 16.2N 106.5W   75 KT  85 MPH
 12H  21/1800Z 16.8N 107.0W   85 KT 100 MPH
 24H  22/0600Z 17.6N 107.4W  100 KT 115 MPH
 36H  22/1800Z 18.7N 107.7W  115 KT 130 MPH
 48H  23/0600Z 19.8N 107.7W  120 KT 140 MPH
 72H  24/0600Z 22.3N 106.1W   90 KT 105 MPH...NEAR WNCTRL MEXICO
 96H  25/0600Z 26.9N 101.2W   25 KT  30 MPH...INLAND NCNTRL MEXICO

Forecaster Stewart