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Hurricane Gilma Discussion Number  25
NWS National Hurricane Center Miami FL       EP072024
500 AM HST Sat Aug 24 2024

Gilma continues to show a well-defined, but somewhat asymmetric, 
central dense overcast in satellite imagery.  AMSR microwave data 
near 1000 UTC showed an eye and eyewall are still present under the 
overcast, and the eye makes occasional attempts to appear in 
infrared imagery.  The various subjective and objective intensity 
estimates currently have a wide range from 65-90 kt.  However, the 
overall trend of these estimates is down, and based on this the 
initial intensity is reduced to a somewhat uncertain 80 kt.

The initial motion is 275/8 kt.  A mid-level ridge is forecast to 
gradually build to the north of Gilma during the next several days, 
and this should steer the cyclone on a generally westward, or just 
north of westward, track through the forecast period.  The guidance 
has shifted south since the last advisory, continuing a trend that 
started yesterday.  Based on this guidance, the new forecast track 
is also adjusted a little south of the previous track.

Gilma is expected to remain over sea surface temperatures (SSTs) 
near 26C for the next day or two, and since it is in a light shear 
environment, only slow weakening is expected during this time.  
After that time, increasing westerly shear and dry air entrainment 
is likely to lead to significant weakening, even though the SSTs 
along the forecast track remain near 25-26C. While this is the most 
likely scenario, some differences have developed in the intensity 
guidance.  The global models and the HMON regional model generally 
show Gilma degenerating to a post tropical cyclone by 96 h and to a 
remnant low by 120 h. On the other hand, the latest HWRF, HAFS-A, 
and HAFS-B runs show the cyclone remaining a convection producing 
tropical storm through the end of the forecast period.  Given the 
forecast shear and dry air, these forecasts look too strong, and the 
new intensity forecast will follow the global model solutions of a 
faster decay.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  24/1500Z 17.6N 130.0W   80 KT  90 MPH
 12H  25/0000Z 17.7N 131.3W   80 KT  90 MPH
 24H  25/1200Z 17.9N 133.1W   80 KT  90 MPH
 36H  26/0000Z 18.1N 134.8W   75 KT  85 MPH
 48H  26/1200Z 18.3N 136.6W   70 KT  80 MPH
 60H  27/0000Z 18.5N 138.5W   60 KT  70 MPH
 72H  27/1200Z 18.7N 140.6W   50 KT  60 MPH
 96H  28/1200Z 19.3N 145.0W   35 KT  40 MPH...POST-TROPICAL
120H  29/1200Z 20.0N 149.5W   30 KT  35 MPH...POST-TROP/REMNT LOW
 
$$
Forecaster Beven
 
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