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Tropical Storm Dorian Forecast Discussion Number 11
2019-08-27 04:44:15| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Mon Aug 26 2019 000 WTNT45 KNHC 270244 TCDAT5 Tropical Storm Dorian Discussion Number 11 NWS National Hurricane Center Miami FL AL052019 1100 PM AST Mon Aug 26 2019 An Air Force Reserve Unit Hurricane Hunter aircraft has been investigating Dorian this evening. Data from the plane indicate that the storm is not quite as strong as previously estimated, and based on flight-level winds and SFMR-observed surface winds the intensity is set at 45 kt. Fixes from the aircraft show that the center of the cyclone moved just south of the southern coast of Barbados within the last couple of hours, and tropical-storm-force winds were reported over that island. There is fairly well-defined upper-level outflow over the eastern semicircle of the circulation. Although some dry mid-level air is likely to continue to affect Dorian while it moves over the northeastern Caribbean, the dynamical guidance indicates that the shear will not become very strong. Therefore it is still expected that the cyclone will become a hurricane in a couple of days. Some disruption of the system will likely occur when the center moves near eastern Hispaniola. The official intensity forecast is on the high end of the model guidance and is subject to considerable uncertainty, particularly from days 3 to 5. Dorian continues to move west-northwestward, or 290/11 kt, while being steered by the flow on the south side of the subtropical ridge. In a day or two, the tropical cyclone is expected to turn northwestward due to a weakness in the ridge. The ridge is expected to build somewhat later in the forecast period, which should cause Dorian to turn slightly to the left. The ECMWF model is near the northern side of the guidance suite and the UKMET is near the southern side. The GFS model continues to practically dissipate the system so it was unable to generate a forecast track. The official track forecast was shifted a bit to the north, but lies south of the latest dynamical model consensus. It is advisable that one not focus on small changes in the forecast track due to uncertainties. Key Messages: 1. Dorian is expected to bring tropical storm conditions to portions of the Lesser Antilles through Tuesday morning, where tropical storm watches and warnings are in effect. Rainfall of 3 to 8 inches is expected from Martinique to St. Vincent, including Barbados, with isolated totals as high as 10 inches possible. 2. Tropical storm conditions are possible in Puerto Rico on Wednesday, where a tropical storm watch has been issued. Rainfall of 2 to 4 inches with maximum totals of 6 inches are possible across Puerto Rico and St. Croix. 3. Watches will likely be issued for portions of Hispaniola early Tuesday, as the threat of wind and rain impacts continues to increase. 4. While uncertainty is high, wind and rain impacts are possible in the Bahamas and Florida later this week and this weekend. Residents in these areas should monitor the progress of Dorian and ensure that they have their hurricane plan in place. FORECAST POSITIONS AND MAX WINDS INIT 27/0300Z 13.2N 59.7W 45 KT 50 MPH 12H 27/1200Z 14.0N 61.3W 50 KT 60 MPH 24H 28/0000Z 15.2N 63.5W 55 KT 65 MPH 36H 28/1200Z 16.5N 65.5W 60 KT 70 MPH 48H 29/0000Z 17.9N 67.6W 65 KT 75 MPH 72H 30/0000Z 21.0N 71.0W 50 KT 60 MPH 96H 31/0000Z 24.0N 74.8W 55 KT 65 MPH 120H 01/0000Z 26.5N 79.0W 60 KT 70 MPH $$ Forecaster Pasch
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