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| #1140141 (Received by flhurricane at: 10:47 AM 20.Jun.2023) TCDAT3 Tropical Storm Bret Discussion Number 5 NWS National Hurricane Center Miami FL AL032023 1100 AM AST Tue Jun 20 2023 Bret`s low-level center has become exposed this morning, surrounded by bands of deep convection in nearly all quadrants. Upper-level outflow still appears established over the system, but the exposed center may suggest that some moderate westerly shear is affecting Bret below the cirrus level. Bret`s initial intensity remains 35 kt based on T2.5 Dvorak classifications from TAFB and SAB. Scatterometer passes continue to miss Bret, keeping us from getting a better handle on the system`s intensity and size. Global model forecast fields suggest that the mid-level westerly shear affecting Bret is unlikely to abate during the next few days, and it`s likely that deeper-layer shear will also increase in about 2 to 3 days. This forecast scenario has led to some changes in Bret`s intensity forecast. Aside from the HWRF, which is an outlier scenario, none of the other reliable intensity models bring Bret to hurricane intensity. In addition, all of the global models show Bret opening up into a trough in 2 to 4 days as it`s passing the Lesser Antilles or after it moves into the eastern Caribbean Sea. As a result, Bret`s forecast intensity in the NHC prediction has been decreased, still allowing for the possibility of some strengthening, but keeping the system below hurricane strength. In addition, the new forecast now shows dissipation by day 5, but if the global models are correct, that could occur even sooner. Bret is moving a little faster toward the west, or 275/18 kt. Low- to mid-level ridging over the Atlantic is expected to keep Bret on a westward trajectory through the forecast period, with only some slight fluctuations in forward speed. The track guidance has shifted southward on this cycle, under the assumption that low-level ridging will have a greater impact on preventing a weaker Bret from gaining much latitude. One important note is that the weaker Bret remains, it could also move faster than what is shown in the NHC forecast (and what is suggested by the ECWMF model). KEY MESSAGES: 1. Bret is forecast to approach the Lesser Antilles through early Thursday and then move across the islands Thursday and Thursday night as a tropical storm, bringing a risk of flooding from heavy rainfall, strong winds, and dangerous waves along the coast. 2. Given the larger-than-usual uncertainty in the track and intensity forecasts, it is too early to specify the location and magnitude of where Bret`s associated hazards could occur. However, everyone in the Lesser Antilles, Puerto Rico, and the Virgin Islands should closely monitor updates to the forecast for Bret. Tropical storm watches may be required for portions of the Lesser Antilles later today or tonight. FORECAST POSITIONS AND MAX WINDS INIT 20/1500Z 11.9N 47.0W 35 KT 40 MPH 12H 21/0000Z 12.3N 49.2W 40 KT 45 MPH 24H 21/1200Z 12.7N 51.9W 45 KT 50 MPH 36H 22/0000Z 13.2N 54.5W 50 KT 60 MPH 48H 22/1200Z 13.6N 57.3W 55 KT 65 MPH 60H 23/0000Z 13.9N 60.4W 55 KT 65 MPH 72H 23/1200Z 14.2N 63.6W 50 KT 60 MPH 96H 24/1200Z 14.4N 70.4W 45 KT 50 MPH 120H 25/1200Z...DISSIPATED $$ Forecaster Berg |
