Hurricane Gilma Forecast Discussion
000 WTPZ42 KNHC 230234 TCDEP2 Hurricane Gilma Discussion Number 19 NWS National Hurricane Center Miami FL EP072024 500 PM HST Thu Aug 22 2024 Gilma's satellite presentation has degraded this evening, with the eye becoming cloud filled and more irregularly shaped. Dvorak Current Intensity estimates remain unchanged from TAFB (6.0/115 kt) and SAB (5.5/102 kt) from earlier today, but most objective numbers from UW-CIMSS now range between 95 and 105 kt. 105 kt is set as the initial intensity as a blend of these numbers and the general degradation of the eye definition. Gilma's forward speed is now down to 5 kt toward the west-northwest. A deep-layer trough over the U.S. West Coast is expected to gradually move eastward, allowing mid-level high pressure to build offshore. This should cause Gilma to very gradually accelerate toward the west-northwest and then west through the entire 5-day forecast period. There is high confidence in Gilma's forecast track given a tightly packed guidance suite, and the updated NHC track prediction has only been pushed northward a shade, following the latest consensus trends. On the current forecast track, Gilma would move into the central Pacific basin late Monday. The ocean heat content near Gilma is only about 8 units (for reference, ocean heat content in the northwestern Caribbean Sea and Gulf of Mexico exceeds 100 units). Therefore, it is likely that the hurricane's very slow motion is upwelling cold water from below, which may be contributing to the recent degradation in the satellite appearance. Cold water upwelling will probably continue for the next couple of days while Gilma's forward speed remains 8 kt or less, and despite a relatively low-shear environment, gradual weakening is forecast to continue through the entire forecast period. The new NHC forecast has been adjusted downward, but it still lies near the northern bound of the guidance suite. Global model guidance suggests that the cool waters, a drier environment, and increased shear may cause Gilma to struggle to maintain deep convection by early next week, and the new forecast now shows the cyclone becoming post tropical by day 5. FORECAST POSITIONS AND MAX WINDS INIT 23/0300Z 17.3N 125.5W 105 KT 120 MPH 12H 23/1200Z 17.6N 126.6W 100 KT 115 MPH 24H 24/0000Z 18.0N 128.1W 95 KT 110 MPH 36H 24/1200Z 18.4N 129.8W 90 KT 105 MPH 48H 25/0000Z 18.8N 131.5W 85 KT 100 MPH 60H 25/1200Z 19.0N 133.3W 80 KT 90 MPH 72H 26/0000Z 19.2N 135.3W 70 KT 80 MPH 96H 27/0000Z 19.8N 139.8W 55 KT 65 MPH 120H 28/0000Z 20.5N 145.3W 35 KT 40 MPH...POST-TROPICAL $$ Forecaster Berg
Originally Posted at:
NATIONAL HURRICANE CENTER and CENTRAL PACIFIC HURRICANE CENTER
At The NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION
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