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Tropical Depression Gilma Discussion Number  46
NWS Central Pacific Hurricane Center Honolulu HI   EP072024
500 AM HST Thu Aug 29 2024
 
Gilma's satellite presentation continues to degrade. A few strong 
thunderstorms developing north of Gilma's weakening low-level 
circulation center are doing little to sustain it as a tropical 
cyclone as they remain well removed from the center, and lack 
significant banding. 0643Z ASCAT and 0918Z Oceansat passes showed 
primarily 25-30 kt winds north of the center, and only isolated 
pockets of 32-34 kt winds, respectively. Given the degraded 
satellite appearance and assuming continued gradual spin-down, the 
initial intensity for this advisory is estimated to be 30 kt.

The initial motion estimate remains 280/12 kt, although the 
potentially elongating low-level circulation center is somewhat 
obscured, leading to a reduction in confidence. A low-level ridge 
to the north will continue to steer Gilma just north of due west 
today, with a turn toward the west-northwest expected Friday as the 
ridge weakens. The updated track forecast is similar to the 
previous forecast, as track guidance remains consistent and well 
clustered. 

Gilma is moving into an area of increasing westerly vertical wind 
shear on the order of 20-30 kt, associated with a trough aloft 
approaching from the west. GFS and ECMWF simulated satellite 
imagery indicate that Gilma will struggle to produce organized deep 
convection, and Gilma will likely become a post-tropical remnant 
low by tonight. The forecast indicates it will continue to gradually 
weaken as it passes just north of the Hawaiian Islands on Friday, 
and dissipate in the vicinity of Kauai on Saturday, in line with 
global model and SHIPS guidance.  
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  29/1500Z 19.7N 150.7W   30 KT  35 MPH
 12H  30/0000Z 20.1N 152.5W   30 KT  35 MPH
 24H  30/1200Z 20.7N 154.9W   30 KT  35 MPH...POST-TROP/REMNT LOW
 36H  31/0000Z 21.6N 157.2W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  31/1200Z 22.6N 159.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
 60H  01/0000Z...DISSIPATED
 
$$
Forecaster Birchard
 
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