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TROPICAL STORM PATRICIA DISCUSSION NUMBER   4
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP202015
400 AM CDT WED OCT 21 2015

The cloud pattern of the storm is not well organized at this time,
with not much deep convection concentrated near the estimated
center position.  There is also a lack of well-defined banding
features.  The current intensity estimate is held at 35 kt, in
agreement with a Dvorak CI Value from TAFB.

The center is not easy to track on nighttime imagery, with a
significant spread in fix locations from TAFB and SAB, and the
initial motion estimate is a rather uncertain 270/6 kt.  The
primary steering features over the next few days are a
mid-tropospheric trough extending southward into extreme
northwestern Mexico and a high over the Gulf of Mexico.  This flow
regime should cause Patricia to turn gradually to the right over the
next few days, and cross the coast of southwestern Mexico within 72
hours or so.  The official track forecast resembles the previous
one but is a little faster, and is close to the new model
consensus.  This is between the latest GFS and ECMWF solutions.

Although the tropical cyclone has not strengthened significantly
thus far, the environment seems to be quite conducive for
intensification.  With very warm sea surface temperatures near 30
deg C, light vertical shear, and a very moist atmosphere likely to
prevail during the next couple of days, Patricia is forecast to
strengthen into a hurricane by tomorrow.  The official intensity
forecast is close to the LGEM guidance, but it should be noted that
if the system develops a well-defined inner core, rapid
intensification is certainly possible.  Note that in the official
wind speed forecast shown here, additional strengthening is implied
after the 48 hour forecast and up until landfall.

Based on the new 48-hour forecast location and the predicted wind
radii, A Hurricane Watch and a Tropical Storm Watch have been
issued for portions of the coast of southwestern Mexico.

FORECAST POSITIONS AND MAX WINDS

INIT  21/0900Z 13.0N  96.0W   35 KT  40 MPH
 12H  21/1800Z 13.2N  97.6W   40 KT  45 MPH
 24H  22/0600Z 14.0N  99.8W   50 KT  60 MPH
 36H  22/1800Z 15.1N 101.8W   65 KT  75 MPH
 48H  23/0600Z 16.5N 103.3W   80 KT  90 MPH
 72H  24/0600Z 20.5N 104.0W   85 KT 100 MPH...INLAND
 96H  25/0600Z 23.0N 104.0W   40 KT  45 MPH...INLAND
120H  26/0600Z...DISSIPATED

$$
Forecaster Pasch

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