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Tropical Depression Gilma Discussion Number 5

Wiki-Hurricanes Forecast Center

2:00 PM PDT Fri Jul 27 2018

Gilma's center of circulation has progressively outpaced the main swath of convective activity to the circulation's southeast this afternoon, and has detached even further since this morning. The system's northern semicricle remains quite subsident, and is entraining into the tropical cyclone via the storm's west. Some additional convection has attempted to fire near Gilma's center along a singular cloud band, but the low-level center remains exposed and will continue to remain exposed unless the storm's moisture envelope is able to siphon off subsident conditions. UW-CIMSS ADT estimated raw satellite intensity values of T1.5/25kt, with SAB providing a subjective estimate of T2.0/30kt. Given good consensus and the apparent lack of organization while acknowledging the tropical storm intensity from earlier, Gilma's intensity has been lowered to 30kt, making it a tropical depression. However, it would be ideal if scatterometer data were available to sample the intensity of Gilma's wind field.

No changes to the forecast track regime with Gilma moving westward as anticipated under the influence of subtropical ridging. Gilma's current structure is not very supportive of intensification, and global and statistical guidance are in decent agreement that wind shear will continue to plague Gilma and prevent intensification despite warm sea surface temperatures. Some dynamical gudiance show a small window for intensification in the 12-24 hour window, but this does not seem particularly convincing given that shear is expected to remain strong and allow for additional interference from dry air throughout the forecast period. The current intensity forecast no longer shows additional strengthening, and degenerates Gilma into a remnant low by 72 hours, if not before then.

FORECAST POSITIONS AND MAX WINDS

INIT 27/2100Z 30 KT 35 MPH

12H 28/0600Z 30 KT 35 MPH

24H 28/1800Z 30 KT 35 MPH

36H 29/0600Z 25 KT 30 MPH

48H 29/1800Z 25 KT 30 MPH

72H 30/1800Z 20 KT 25 MPH...POST-TROP/REMNT LOW

96H 31/1800Z...DISSIPATED

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