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Tropical Storm Gabrielle Forecast Discussion Number 23
2019-09-09 04:32:43| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Sun Sep 08 2019 000 WTNT43 KNHC 090232 TCDAT3 Tropical Storm Gabrielle Discussion Number 23 NWS National Hurricane Center Miami FL AL082019 1100 PM AST Sun Sep 08 2019 Gabrielle's cloud pattern has not become better organized since earlier today. The central convection has become a little more fragmented, and the center is estimated to be near the northern side of the main area of convection. There is a well-defined upper-level outflow jet over the southern portion of the circulation. The initial intensity is held at 55 kt in agreement with the latest Dvorak Current Intensity number from TAFB, although this may be generous given a recent ASCAT overpass of the storm. Gabrielle's window for additional strengthening should soon close, since the cyclone will be over warm waters for less than 24 hours, and the dynamical models indicate a significant increase in vertical shear during the next day or so. Therefore, only a slight short-term increase in strength seems likely. The official intensity forecast is in fairly good agreement with the latest corrected consensus guidance, HCCA. By 48 hours, the global models depict the cyclone as embedded within a baroclinic zone over the mid-latitudes of the Atlantic. Therefore, the official forecast shows Gabrielle becoming extratropical by that time. By 96 hours, the system should become absorbed by a large low pressure system at high latitudes. The initial motion is northward, or 360/13 kt. The track forecast philosophy is basically unchanged. Over the next 1 to 2 days, Gabrielle should turn northeastward and accelerate as it moves around the northwestern periphery of a mid-level high centered near the Azores. Later on, the cyclone should accelerate further within the mid-latitude west-southwesterly flow. The official forecast is very close to the previous NHC track, and close to the corrected consensus prediction. Based on the ASCAT data, the 34-kt wind radii over the southern semicircle of the circulation were increased a bit. FORECAST POSITIONS AND MAX WINDS INIT 09/0300Z 36.5N 49.3W 55 KT 65 MPH 12H 09/1200Z 38.6N 47.8W 60 KT 70 MPH 24H 10/0000Z 41.1N 44.7W 55 KT 65 MPH 36H 10/1200Z 43.6N 40.4W 50 KT 60 MPH 48H 11/0000Z 46.5N 35.2W 45 KT 50 MPH...POST-TROP/EXTRATROP 72H 12/0000Z 54.5N 18.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 96H 13/0000Z...DISSIPATED $$ Forecaster Pasch
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