Tropical Storm Gilma Forecast Discussion

295 
WTPZ42 KNHC 201434
TCDEP2

Tropical Storm Gilma Discussion Number   9
NWS National Hurricane Center Miami FL       EP072024
800 AM PDT Tue Aug 20 2024

Deep convection has increased significantly over the past several 
hours, but the center is located near the northeastern edge of the 
thunderstorms.  This asymmetric structure is due to 15-20 kt of 
northeasterly vertical wind shear.  The objective and subjective 
Dvorak estimates range from 35 to 55 kt, and based on that data, 
the initial intensity is held at 45 kt.  However, this estimate 
could be a little conservative based on recent satellite trends.

Gilma's motion has been somewhat erratic, but smoothing through the 
wobbles yields an initial motion estimate of 285/10 kt.  A high 
pressure ridge situated to the north of the storm should cause that 
motion to continue for another day or so.  However, after that 
time, a decrease in forward speed is expected as the ridge weakens 
and is replaced by a broad trough.  The models have trended south 
this cycle, and the NHC track forecast has been nudged in that 
direction.

The ongoing northeasterly vertical wind shear is expected to 
decrease and become fairly low during the next few days.  This more 
conducive upper-level wind pattern combined with warm SSTs and high 
moisture should allow Gilma to steadily strengthen through the rest 
of the week.  Gilma is forecast to reach hurricane strength by 
Wednesday night and could reach its peak intensity a day later.  By 
the end of the week, the cyclone is expected to track over cooler 
waters and into a more stable airmass, which should induce a 
weakening trend.  The NHC intensity forecast is similar to the 
previous one.


FORECAST POSITIONS AND MAX WINDS

INIT  20/1500Z 16.0N 119.6W   45 KT  50 MPH
 12H  21/0000Z 16.2N 121.0W   50 KT  60 MPH
 24H  21/1200Z 16.6N 122.6W   55 KT  65 MPH
 36H  22/0000Z 17.0N 123.9W   65 KT  75 MPH
 48H  22/1200Z 17.4N 125.0W   75 KT  85 MPH
 60H  23/0000Z 17.8N 126.0W   85 KT 100 MPH
 72H  23/1200Z 18.3N 127.3W   85 KT 100 MPH
 96H  24/1200Z 19.2N 129.7W   75 KT  85 MPH
120H  25/1200Z 20.0N 132.7W   60 KT  70 MPH

$$
Forecaster Cangialosi