Hurricane Gilma Forecast Discussion

358 
WTPZ42 KNHC 270247
TCDEP2

Hurricane Gilma Discussion Number  36
NWS National Hurricane Center Miami FL       EP072024
500 PM HST Mon Aug 26 2024

Gilma remains a resilient hurricane over the far western portion of 
the Eastern Pacific. Its eye is distinct and surrounded by a healthy 
ring of cold -60 to -70C cloud tops. Both a GMI and AMSR2 microwave 
pass received after the prior advisory also highlight Gilma's 
well-organized structure, primarily in the form of a single closed 
eyewall. However, the eyewall does appear to be weaker on its 
southern side, which might be a harbinger of increasing westerly 
vertical wind shear finally beginning to impact the inner-core 
structure. In the meantime, subjective and objective intensity 
estimates are largely unchanged from earlier this afternoon, and the 
initial intensity is held at 95 kt for this advisory. 

Gilma continues on a just north of due westward track, though a 
little faster than earlier at 280/10 kt. A prominent subtropical 
ridge to its north should continue to steer the hurricane generally 
westward to west-northwestward with a gradual increase in forward 
motion over the next several days. On this track, Gilma should enter 
the Central Pacific basin by tomorrow morning. The deep-layer 
ridging does weaken towards the end of the forecast period, but 
Gilma will also likely become more vertically shallow at that time. 
The track guidance this cycle once again is a bit faster than the 
prior one, and the NHC track forecast is also a little faster than 
the previous one, blending the consensus aids TCVE and HCCA with the 
prior track forecast. 

While Gilma has defied the odds and remained stronger than 
forecasted over the past couple of days, there is evidence that 
westerly vertical wind shear is beginning to impinge on the 
hurricane. SHIPS guidance shows this shear gradually increasing as 
Gilma also traverses a very dry mid-level environment and only 
marginal 25-26 C sea-surface temperatures. Assuming this dry air is 
ultimately entrained into its inner core, weakening should begin 
soon. After 48-60 h, the EC-SHIPS shows the shear increasing to more 
than 30 kt, which will likely continue this weakening trend even as 
Gilma begins to move over warmer waters again. The NHC intensity 
forecast is similar to the prior advisory, just a little on the high 
side of the intensity consensus early on. Both the GFS and ECMWF 
suggest the system will cease to produce organized convection after 
72 h, with remnant low status forecast after that time, and final 
dissipation by 120 h.


FORECAST POSITIONS AND MAX WINDS

INIT  27/0300Z 18.5N 138.3W   95 KT 110 MPH
 12H  27/1200Z 18.6N 140.0W   85 KT 100 MPH
 24H  28/0000Z 18.8N 142.2W   70 KT  80 MPH
 36H  28/1200Z 19.1N 144.4W   55 KT  65 MPH
 48H  29/0000Z 19.6N 146.6W   50 KT  60 MPH
 60H  29/1200Z 20.1N 148.7W   45 KT  50 MPH
 72H  30/0000Z 20.5N 151.0W   35 KT  40 MPH
 96H  31/0000Z 21.7N 155.5W   30 KT  35 MPH...POST-TROP/REMNT LOW
120H  01/0000Z...DISSIPATED

$$
Forecaster Papin