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Tropical Storm Sebastien Forecast Discussion Number 6
2019-11-20 21:37:55| National Hurricane Center (Atlantic)
Issued at 500 PM AST Wed Nov 20 2019 000 WTNT45 KNHC 202037 TCDAT5 Tropical Storm Sebastien Discussion Number 6 NWS National Hurricane Center Miami FL AL202019 500 PM AST Wed Nov 20 2019 Sebastien has changed little in organization today, with northwesterly shear displacing the deep convection to the southeast of an exposed low-level center. An ASCAT-C overpass late this morning sampled peak winds of 41 kt, and so the initial advisory intensity will remain 45 kt due to the assumption of undersampling by the scatterometer. Sebastien made its anticipated turn to the north earlier today, and the current motion is now 360/05 kt. The cyclone should turn to the northeast tonight and begin to accelerate as it gets embedded in increasing southwesterly flow ahead of an approaching cold front and associated mid- to upper- level trough. The official forecast track is near the previous one through 24 hours, and a little slower and to the south of it beyond that time due to a shift in the model guidance. The approaching trough should provide a diffluent environment aloft over Sebastien beginning tonight and persisting until the system makes the transition to an extratropical cyclone in a couple of days. This is expected to result in some intensification over the next day or so. Once extratropical, the cyclone should gradually become absorbed into a frontal zone through the end of the week. The official forecast is changed little from the previous one, and is near the IVCN consensus. FORECAST POSITIONS AND MAX WINDS INIT 20/2100Z 21.7N 61.5W 45 KT 50 MPH 12H 21/0600Z 22.7N 61.0W 50 KT 60 MPH 24H 21/1800Z 24.5N 59.0W 60 KT 70 MPH 36H 22/0600Z 27.2N 55.5W 60 KT 70 MPH 48H 22/1800Z 30.0N 51.4W 60 KT 70 MPH...POST-TROP/EXTRATROP 72H 23/1800Z...DISSIPATED $$ Forecaster Latto
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