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Hurricane Gilma Discussion Number  20
NWS National Hurricane Center Miami FL       EP072024
1100 PM HST Thu Aug 22 2024
 
The satellite presentation of Gilma has not changed much since the 
previous advisory. The ragged eye of the hurricane is still 
surrounded by deep convection, with the coldest cloud tops located 
over the western and southern portions of the inner core. Based on 
consensus T-5.5/102 kt Dvorak current intensity estimates from TAFB 
and SAB, and similar estimates from the various UW-CIMSS objective 
techniques, the initial intensity is held at 105 kt.

The center of the hurricane has jogged westward during the past few 
hours, but the longer-term motion is still west-northwestward at 
about 5 kt. A deep-layer trough near the west coast of the United 
States is expected to lift out over the next couple of days, which 
will allow a high pressure ridge to build westward over the eastern 
North Pacific. As a result, Gilma should gradually move faster 
toward the west-northwest and west during the next several days. The 
track guidance remains tightly clustered, and the NHC forecast is 
essentially an update of the previous one with no notable changes.

As previously discussed, the slow forward speed of Gilma is likely 
resulting in some upwelling of cooler waters underneath the 
hurricane. Although the vertical wind shear is forecast to remain 
relatively weak during the next couple of days, the track of Gilma 
will bring the hurricane over even cooler waters and into a drier 
mid-level environment by this weekend. These factors suggest at 
least gradual weakening should continue in the near term, followed 
by more significant weakening beyond 72 h as the cyclone encounters 
stronger shear and the upper air pattern becomes more convergent. 
Some slight downward adjustments were made to the NHC prediction 
later in the period. Gilma is forecast to become a post-tropical 
cyclone by 120 h, but the lack of organized convection in GFS and 
ECMWF model-simulated satellite imagery indicates this transition 
could occur as early as day 4.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  23/0900Z 17.4N 126.1W  105 KT 120 MPH
 12H  23/1800Z 17.6N 127.2W  100 KT 115 MPH
 24H  24/0600Z 18.0N 128.8W   95 KT 110 MPH
 36H  24/1800Z 18.4N 130.5W   90 KT 105 MPH
 48H  25/0600Z 18.7N 132.2W   80 KT  90 MPH
 60H  25/1800Z 19.0N 134.1W   70 KT  80 MPH
 72H  26/0600Z 19.3N 136.1W   65 KT  75 MPH
 96H  27/0600Z 19.9N 140.8W   50 KT  60 MPH
120H  28/0600Z 20.5N 146.0W   35 KT  40 MPH...POST-TROPICAL
 
$$
Forecaster Reinhart
 
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