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Hurricane Dorian Forecast Discussion Number 56
2019-09-07 10:39:54| National Hurricane Center (Atlantic)
Issued at 500 AM AST Sat Sep 07 2019 460 WTNT45 KNHC 070839 TCDAT5 Hurricane Dorian Discussion Number 56 NWS National Hurricane Center Miami FL AL052019 500 AM AST Sat Sep 07 2019 Dorian is gradually becoming less organized. The cyclone is feeling some effects of southwesterly wind shear with most of its deep convection located to the north and east of the estimated center. The initial intensity is lowered a little to 75 kt, which is in good agreement with the latest Dvorak CI-numbers from TAFB and SAB. A pair of ASCAT passes from several hours ago indicate that the wind field has expanded significantly, and tropical-storm-force winds have been observed over far southeastern Massachusetts. Dorian is racing northeastward, with the latest initial motion estimated to be 050/22 kt. The hurricane is well embedded in the fast mid-latitude flow, and it should continue to move quickly northeastward toward Nova Scotia later today. After the cyclone passes Nova Scotia, it is forecast to move through Newfoundland and Labrador before turning east-northeastward over the far north Atlantic. The NHC track forecast is largely an update of the previous one and not far from the various consensus aids. Dorian is expected to gradually weaken due to even stronger southwesterly wind shear and much colder SSTs to the north of the Gulf Stream current. The combined influences of these cold waters and an approaching mid- to upper-level trough should cause Dorian to lose its tropical characteristics in about 24 hours. However, the post-tropical cyclone will likely still be producing hurricane-force winds as it moves through portions of eastern Canada. The global models are in good agreement that the post-tropical cyclone should slowly weaken and ultimately become absorbed by another extratropical low in 3 to 4 days. The NHC intensity forecast is in best agreement with the GFS and ECMWF models, which typically handle large extratropical lows better that than the intensity models that are made for tropical cyclones. Key Messages: 1. Regardless of whether it is a hurricane or a post-tropical cyclone, Dorian is expected to have a significant impact in portions of eastern Canada beginning later today. Dangerous storm surge impacts are likely in portions of the Gulf of St. Lawrence, southwestern Newfoundland and eastern Nova Scotia. Hurricane-force winds are also likely in Nova Scotia, Prince Edward Island and Newfoundland later today and tonight. Refer to information from the Canadian Hurricane Centre for more information on these hazards. FORECAST POSITIONS AND MAX WINDS INIT 07/0900Z 39.7N 68.1W 75 KT 85 MPH 12H 07/1800Z 42.8N 64.9W 70 KT 80 MPH 24H 08/0600Z 46.9N 61.6W 65 KT 75 MPH...POST-TROP/EXTRATROP 36H 08/1800Z 50.0N 58.0W 55 KT 65 MPH...POST-TROP/EXTRATROP 48H 09/0600Z 52.5N 52.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 72H 10/0600Z 57.5N 36.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 96H 11/0600Z...DISSIPATED $$ Forecaster Cangialosi
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