Hurricane Gilma Forecast Discussion

000
WTPZ42 KNHC 260831
TCDEP2

Hurricane Gilma Discussion Number  33
NWS National Hurricane Center Miami FL       EP072024
1100 PM HST Sun Aug 25 2024

This evening's satellite presentation consists of a ragged
partially obscured eye with a small inner core open in the south
semi-circle.  Gilma's cloud pattern continues to deteriorate slowly
and has shed most of the associated convective bands with the
exception of fragmented curved band wrapping in from the south.
The initial intensity is lowered to 85 kt and is based on the
Dvorak satellite intensity estimates from TAFB and SAB and a blend
of the UW-CIMSS ADT, AiDT, and DMINT objective estimates, yielding
83 kt.

Water vapor imagery and global model RH/700mb fields indicate that
the cyclone is moving toward a dry, stable air mass, indicative of
a large low-level stratocumulus cloud deck intruding from the
northwest in the GOES-18 Proxy-VIS images.  Subsequently, the
statistical GFS/ECMWF SHIPS indicated a mid-level/700-500mb RH of
42 percent.  This inhibiting thermodynamic contribution, along with
increasing west-to-west-southwesterly shear noted in the
statistical SHIPS intensity guidance, particularly beyond 36 hrs,
should cause Gilma to weaken at a quicker rate through day 5.
The NHC intensity forecast is a compromise of the Decay-SHIPS and
the IVCN intensity consensus and shows Gilma degenerating to a
post-tropical cyclone in 4 days.

Gilma's initial motion is estimated to be westward, or 280/8 kt,
and is moving in the southern periphery of a mid-tropospheric
subtropical ridge extending westward across the tropical-eastern
Pacific from northwestern Mexico.  The global and regional models
are fairly clustered together and indicate a slightly to the right
of the initial track motion, or west-northwestward beyond the 60 hr 
period, and the official forecast follows suit.  Along-track 
differences continue to be a model inconsistency, but following the 
skilled TVCE and HCCA consensus models have been the best track 
forecast solution so far.

Gilma's 50 kt wind radii have been slightly adjusted based on a 
0559 UTC METOP-C ASCAT overpass.


FORECAST POSITIONS AND MAX WINDS

INIT  26/0900Z 18.1N 135.9W   85 KT 100 MPH
 12H  26/1800Z 18.3N 137.1W   80 KT  90 MPH
 24H  27/0600Z 18.5N 138.9W   70 KT  80 MPH
 36H  27/1800Z 18.7N 140.9W   65 KT  75 MPH
 48H  28/0600Z 19.0N 143.0W   60 KT  70 MPH
 60H  28/1800Z 19.4N 145.0W   50 KT  60 MPH
 72H  29/0600Z 19.8N 147.0W   45 KT  50 MPH
 96H  30/0600Z 20.6N 151.0W   35 KT  40 MPH...POST-TROPICAL
120H  31/0600Z 21.6N 155.7W   30 KT  35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Roberts