ZCZC MIATCDEP4 ALL
TTAA00 KNHC DDHHMM

Tropical Storm Willa Discussion Number   4
NWS National Hurricane Center Miami FL       EP242018
900 PM MDT Sat Oct 20 2018

Willa has rapidly intensified since genesis occurred last night,
and it is almost a hurricane.  Geostationary satellite and
microwave images indicate that banding features have become well
established in all quadrants and the inner core has continued to
organize.  There is still no evidence of an eye feature,
however.  A blend of the latest satellite intensity estimates
supports increasing the initial wind speed to 60 kt.

The latest satellite fixes indicate that Willa is now moving
northwestward at about 5 kt.  The storm is expected to gradually
turn to the right as it moves around the western periphery of a
mid-level ridge.  In response, a northwestward motion should
continue for another day or so, followed by a turn toward the north
on Monday.  After that time, a faster north-northeast to northeast
motion is expected when a shortwave trough approaches the system.
The latest model guidance, except for the UKMET, show Willa making
a sharper northward turn and at a faster pace.  The NHC track
forecast has been adjusted accordingly to be in better agreement
with the latest consensus aids.  This forecast is again faster than
the previous one and shows Willa making landfall over west-central
Mexico in 72 to 96 hours.

The storm has taken advantage of near ideal environmental conditions
of very low wind shear, high levels of moisture, and warm 29 deg C
SSTs.  These conditions are expected to prevail for another couple
of days, and that should allow Willa to continue to strengthen
rapidly.  In fact, the SHIPS Rapid Intensification (RI) indices
show about 90 percent chance of RI continuing during the next 24
hours.  Based on this information and the latest model guidance, the
NHC intensity forecast shows Willa becoming a major hurricane in a
day or so.  Some weakening is likely before Willa reaches the coast
due to an increase in shear and a decrease in available moisture,
but Willa is forecast to be a hurricane when it reaches the
coastline.  After landfall, rapid weakening is expected due to
interaction with the rugged terrain.

FORECAST POSITIONS AND MAX WINDS

INIT  21/0300Z 15.7N 106.1W   60 KT  70 MPH
 12H  21/1200Z 16.1N 106.6W   80 KT  90 MPH
 24H  22/0000Z 16.9N 107.1W   95 KT 110 MPH
 36H  22/1200Z 17.7N 107.5W  110 KT 125 MPH
 48H  23/0000Z 18.7N 107.8W  110 KT 125 MPH
 72H  24/0000Z 20.7N 107.3W   90 KT 105 MPH
 96H  25/0000Z 24.1N 104.2W   35 KT  40 MPH...INLAND
120H  26/0000Z...DISSIPATED

$$
Forecaster Cangialosi

NNNN