Tropical Storm Gilma Forecast Discussion

000
WTPZ42 KNHC 202057
TCDEP2

Tropical Storm Gilma Discussion Number  10
NWS National Hurricane Center Miami FL       EP072024
200 PM PDT Tue Aug 20 2024

Gilma has become much better organized throughout the day.  The
center is now embedded in the thunderstorm activity, and the
associated deep convection has been expanding and has a less sheared
appearance.  The Dvorak estimates have increased and are between 45
and 55 kt at 18Z.  Over the past hour or two, a pair of ASCAT passes
showed reliable winds in the 50-55 kt range.  Based on the ASCAT
data and the improving satellite appearance, the initial intensity
is increased to 60 kt.

Gilma is moving westward or 280 degrees at 10 kt.  A high pressure
ridge situated to the north of the storm should cause it to continue
westward to west-northwestward at about the same speed for another
day or so.  However, after that time, a decrease in forward speed
and a slight turn to the right are expected as the ridge weakens and
is replaced by a broad trough.  The NHC track forecast has again
been nudged to the south, toward the latest consensus aids.

The improving cloud pattern suggests that the vertical wind shear
around Gilma is lessening.  In addition, the storm is forecast to
remain over warm waters and in a relatively moist airmass for a few
days.  Therefore, continued steady strengthening is predicted, and
Gilma is expected to become a hurricane tonight or early Wednesday
with additional strengthening anticipated through Thursday.  By the
end of the week, however, the cyclone is expected to track over
cooler waters and into a more stable airmass, which should induce a
weakening trend.  The NHC intensity forecast is nudged upward from
the previous one and near the high end of the model guidance.

The initial 34- and 50-kt wind radii have been updated using the
aforementioned ASCAT data.


FORECAST POSITIONS AND MAX WINDS

INIT  20/2100Z 16.1N 120.6W   60 KT  70 MPH
 12H  21/0600Z 16.3N 121.9W   65 KT  75 MPH
 24H  21/1800Z 16.6N 123.2W   70 KT  80 MPH
 36H  22/0600Z 17.0N 124.4W   75 KT  85 MPH
 48H  22/1800Z 17.5N 125.5W   85 KT 100 MPH
 60H  23/0600Z 17.9N 126.6W   90 KT 105 MPH
 72H  23/1800Z 18.4N 128.0W   85 KT 100 MPH
 96H  24/1800Z 19.0N 130.6W   75 KT  85 MPH
120H  25/1800Z 19.8N 134.1W   60 KT  70 MPH

$$
Forecaster Cangialosi