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Hurricane Gilma Discussion Number  28
NWS National Hurricane Center Miami FL       EP072024
500 PM HST Sat Aug 24 2024
 
Gilma continues to defy the odds and intensify. The satellite 
depiction over the last several hours has been one of a 
well-organized strengthening hurricane. The eyewall is tightly 
wrapped producing deep convection with lightning depicted in the 
northern eyewall on GLM satellite imagery. Visible imagery shows 
that the eye has become circular, well-defined, and has been 
clearing out. Subjective Dvorak estimates have increased but were 
constrained to T6.0/115 kt from both SAB and TAFB, with both 
agencies reporting higher data-T values. Objective satellite 
intensity estimates from UW-CIMSS range from 105-115 kt. Using a 
blend of these estimates the initial intensity is raised to 110 kt 
for this advisory. Therefore, Gilma's strengthening has met the 
definition of rapid intensification as the system has strengthened 
30 kt in 12 h.
 
The initial motion remains 275/8 kt.  A mid-level ridge to the
north of the hurricane continues to gradually build and strengthen.
This should steer Gilma on a generally westward track through the
forecast period. Model guidance is in fairly good agreement,
although there continues to be some forward speed differences,
particularly towards the end of the period. The NHC forecast is
very similar to the previous advisory.
 
Gilma has managed to rapidly intensify over marginally warm sea 
surface temperatures, and has established a well-defined inner 
core within a very low wind shear environment. The system's 
slightly increasing forward speed may have also allowed it to avoid 
some of the negative impacts from upwelling. Given the higher 
initial intensity there are some changes in the near-term 
intensity forecast, with Gilma maintaining hurricane strength longer 
than previously forecast. As Gilma moves into cooler SSTs and a 
little more wind shear, this will cause a gradual weakening trend to 
ensue. Beyond 24 h the system will begin to move into a drier and 
more stable airmass which should increase the rate of weakening as 
wind shear further increases by days 3-4. Global models show Gilma 
starting to struggle to produce convection around day 5, with the 
NHC forecast depicting Gilma as a remnant low at that time. The NHC 
forecast is above most of the intensity guidance in the near term 
given the higher initial intensity, but is near the simple consensus 
intensity aids as the system begins to weaken.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  25/0300Z 17.8N 131.8W  110 KT 125 MPH
 12H  25/1200Z 17.9N 133.1W  110 KT 125 MPH
 24H  26/0000Z 18.1N 134.9W  100 KT 115 MPH
 36H  26/1200Z 18.3N 136.6W   90 KT 105 MPH
 48H  27/0000Z 18.5N 138.5W   80 KT  90 MPH
 60H  27/1200Z 18.7N 140.4W   70 KT  80 MPH
 72H  28/0000Z 18.9N 142.4W   60 KT  70 MPH
 96H  29/0000Z 19.6N 146.5W   45 KT  50 MPH
120H  30/0000Z 20.3N 150.8W   30 KT  35 MPH...POST-TROP/REMNT LOW
 
$$
Forecaster Kelly
 
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