Tropical Storm Gilma Discussion Number 4
Wiki-Hurricanes Forecast Center
8:00 AM PDT Fri Jul 27 2018
Gilma is feeling the effects of moderately strong northwesterly shear this morning as it tracks westward across the open Pacific. Shortwave infrared imagery optimize for the overnight hours suggest that the center of circulation is decoupled from the rest of the convective activity to the circulation's southeast. SAB and TAFB both estimate T2.0/30kt this morning while UW-CIMSS ADT appears to be analyzing the center improperly, so its higher estimate is disregarded. However, the ASCAT pass of Gilma from around 0520Z suggested gale-force winds were indeed present in a convectively free area northeast of the center. On this basis, the intensity for GIlma is kept at a possibly aggressive 35 kt, keeping it a minimal tropical storm at this time.
The westerly motion of GIlma under subtropical ridging over the southwestern United States as not changed, and Gilma will continue on a more or less westerly or west-northwesterly path for the next five days. While the intensity forecast for Gilma has been meager, the tropical storm's future looks more unfavorable as strong wind shear estimated in excess of 20 kt has begun to impact the system earlier than anticipated. Sea surface temperatures are marginal to slightly favorable throughout the forecast window, but the main inhibiting factors are wind shear and dry air which will combine to make conditions outright hostile after two days. The current intensity philosophy overall continues to show marginal organization this evening into tomorrow morning followed by steady weakening afterwards as conditions become more unfavorable for development.
FORECAST POSITIONS AND MAX WINDS
INIT 27/1500Z 35 KT 40 MPH
12H 28/0000Z 40 KT 45 MPH
24H 28/1200Z 40 KT 45 MPH
36H 29/0000Z 35 KT 40 MPH
48H 29/1200Z 30 KT 40 MPH
72H 30/1200Z 25 KT 30 MPH
96H 31/1200Z 25 KT 30 MPH...POST-TROP/REMNT LOW