Hurricane Gilma Forecast Discussion

695 
WTPZ42 KNHC 210849
TCDEP2

Hurricane Gilma Discussion Number  12
NWS National Hurricane Center Miami FL       EP072024
200 AM PDT Wed Aug 21 2024

Satellite images showed Gilma becoming better organized through the 
night until about 0700 UTC, with the low-level center embedded 
underneath the deep convection.  A 21/0216 SSMIS pass was quite 
helpful showing a more impressive mid-level structure, with the 
low-level center likely located about 20 miles to the northwest of 
the mid-level center.  The latest images since 0700 UTC show a dry 
slot in between the central convective mass and a curved band to the 
northwest of the center.  GOES-West CIRA Proxy-Vis imagery has been 
hinting that the low-level center may be near the NW edge of the 
central convective area rather than under the middle of it. The 
latest subjective intensity estimates were T-4.0/65 kt from both 
TAFB and SAB, and the latest objective intensity estimates from 
UW-CIMSS range from 61-68 kt.  Based on these subjective and 
objective intensity estimates, the initial intensity is bumped up to 
65 kt, making Gilma the second hurricane of the 2024 East Pacific 
hurricane season.

Gilma has been moving due west over the past 12 h at 270/9 kt. A 
mid- to upper-level ridge situated to the north of the cyclone 
should be the primary steering mechanism through the forecast 
period, taking Gilma on a westward to west-northwestward course. A 
broad upper-level trough is forecast to move in well north of Gilma 
Thursday into Friday, which should act to slow Gilma's forward speed 
a bit.  The latest global models indicate that this trough won't 
have much of an influence on causing Gilma to gain latitude.  As a 
result, the track guidance has continued to shift well to the south, 
showing a mostly westward track through the forecast period.  The 
latest NHC forecast has been shifted south of the previous official 
forecast, but still lies closer to the previous official forecast 
than the latest model consensus.  If this trend continues, then 
subsequent NHC forecasts will need to be adjusted southward.

Gilma has been reorganizing structurally as it has gradually to 
steadily strengthened over the past 24 h.  Upper-level winds are 
expected to become more favorable over the next day or so.  Gilma 
should remain over relatively warm SSTs and within a moist enough 
airmass for the next 24 to 48 h to allow for additional steady 
intensification, and the forecast peak intensity remains 90 kt.  By 
the weekend, Gilma should encounter gradually cooling sea surface 
temperatures and drier mid-level air, causing the cyclone to 
gradually weaken.  Only minor changes were made to the official 
intensity forecast.  The intensity forecast is slightly above the 
model consensus during the short term, and near the consensus 
during the latter portion of the forecast period.


FORECAST POSITIONS AND MAX WINDS

INIT  21/0900Z 16.0N 122.3W   65 KT  75 MPH
 12H  21/1800Z 16.1N 123.3W   70 KT  80 MPH
 24H  22/0600Z 16.5N 124.4W   80 KT  90 MPH
 36H  22/1800Z 16.9N 125.6W   90 KT 105 MPH
 48H  23/0600Z 17.2N 126.7W   90 KT 105 MPH
 60H  23/1800Z 17.5N 128.1W   90 KT 105 MPH
 72H  24/0600Z 17.7N 129.6W   85 KT 100 MPH
 96H  25/0600Z 18.3N 132.8W   70 KT  80 MPH
120H  26/0600Z 19.1N 136.7W   60 KT  70 MPH

$$
Forecaster Hagen/Pasch