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| #1140193 (Received by flhurricane at: 4:54 PM 20.Jun.2023) TCDAT3 Tropical Storm Bret Discussion Number 6 NWS National Hurricane Center Miami FL AL032023 500 PM AST Tue Jun 20 2023 A burst of deep convection developed over Bret`s center during the past several hours, although a 1641 UTC AMSR2 microwave pass showed that most of the convective activity is located within a band wrapping around the east side of the circulation. Based on the slightly improved convective structure, the initial intensity is raised to 40 kt, which is a blend of T2.5/35 kt and T3.0/45 kt Dvorak estimates from TAFB and SAB, respectively. Despite upper-level cirrus clouds radiating away from the storm in all quadrants, it still appears that there is some westerly shear affecting the system below the cirrus level. Global model forecasts suggest that this setup will continue for the next couple of days, but it shouldn`t be strong enough to prevent some additional strengthening while Bret approaches the Lesser Antilles. The NHC intensity forecast is very close to the HCCA and IVCN consensus aids through 60 hours, and continues to show Bret crossing the islands as a 55-kt tropical storm. Just after that time, Bret will be approaching an upper-level trough located over the eastern Caribbean Sea, and that feature is likely to cause more significant deep-layer shear over the storm by Friday. Because of the increase in shear, all of the global models show Bret opening up into a trough by day 4. For continuity purposes, the official forecast continues to show a day 4 point, but it`s likely that Bret will have dissipated by then. The initial motion remains westward, or 280/17 kt. There is very little change to the forecast track reasoning, with low- to mid-level ridging expected to steer Bret toward the west until it dissipates by day 4. The track guidance has not shifted any farther south on this cycle, so the new NHC track forecast is very similar to the previous one. Users are reminded that NHC`s track forecasts have average errors of 60 to 75 n mi from 48 to 60 hours, and it is too soon to know exactly where Bret`s center will move across the Lesser Antilles chain. KEY MESSAGES: 1. Bret is forecast to approach the Lesser Antilles through Thursday morning and then move across the islands Thursday afternoon 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 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. A Tropical Storm Watch has been issued for Barbados, and additional watches are likely for other islands within the Lesser Antilles later tonight. FORECAST POSITIONS AND MAX WINDS INIT 20/2100Z 12.2N 48.6W 40 KT 45 MPH 12H 21/0600Z 12.6N 50.8W 45 KT 50 MPH 24H 21/1800Z 13.1N 53.4W 50 KT 60 MPH 36H 22/0600Z 13.5N 55.9W 55 KT 65 MPH 48H 22/1800Z 13.9N 58.8W 55 KT 65 MPH 60H 23/0600Z 14.2N 62.0W 55 KT 65 MPH 72H 23/1800Z 14.4N 65.6W 50 KT 60 MPH 96H 24/1800Z 14.7N 73.0W 40 KT 45 MPH 120H 25/1800Z...DISSIPATED $$ Forecaster Berg |
