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| #1051157 (Received by flhurricane at: 5:06 AM 02.Jul.2021) TCDAT5 Tropical Storm Elsa Discussion Number 7 NWS National Hurricane Center Miami FL AL052021 500 AM AST Fri Jul 02 2021 Elsa appears to be slowly gaining strength as it nears the Lesser Antilles. Deep convection has been increasing, and accordingly, the latest Dvorak estimates have nudged upward. The initial intensity is increased to 50 kt, but some of the estimates are a little higher. Radar data from Barbados indicate that a small inner core could be forming, and it seems likely that the center will pass very near or over the island later this morning. An Air Force Hurricane Hunter aircraft is scheduled to be in the storm in a few hours, and the data collected by the plane should provide a better estimate of Elsa`s intensity and structure. The tropical storm is moving quickly to the west-northwest at about 24 kt. A subtropical ridge should continue to steer Elsa briskly to the west-northwest during the next day or two, taking the storm across the eastern and central Caribbean Sea. After that time, a decrease in forward speed and a gradual turn to the north is expected toward a weakness in the ridge. There has not been much change in the latest model runs with the GFS and UKMET models on the left side of the guidance and the ECMWF still on the right side. The spread in the ensemble members of the GFS and ECMWF is very large and range from tracks across or east of the Bahamas to the Yucatan Peninsula. The NHC track forecast continues to hold steady and lies roughly near the middle of the guidance envelope. As stated in previous discussions, this is a low confidence track forecast given the large spread in the models. In the short term, while Elsa moves across the warm Caribbean waters, some additional strengthening seems likely. However, the fast forward speed of the storm and associated mid-level wind shear should prevent significant intensification. Since the new forecast is a little higher than the previous one and shows peak winds just below hurricane force on Saturday near Haiti, tropical storm warnings have been issued for portions of the Dominican Republic and Haiti and a hurricane watch is now in effect for the southern portion of Haiti out of abundance of caution. The degree of land interaction with the mountainous islands of Hispaniola and Cuba will be a big factor in the future strength of Elsa at days 4 and 5. Like the track forecast, there is a huge model spread with solutions ranging from dissipation in the Caribbean to a category 3 hurricane. Given the uncertainty, the intensity forecast generally keeps the storm steady in strength from 24 to 120 h, and it remains on the low side of the model guidance. It should be noted that the average NHC track errors are 175 miles and 200 miles at days 4 and 5, respectively. Given the larger-than- normal uncertainty and because hazards will extend well away from the center of the storm, users are urged to not focus on the exact forecast points. Key Messages: 1. Tropical storm conditions are expected to begin later this morning in portions of the Windward and Leeward Islands. Tropical storm conditions are expected and hurricane conditions are possible over southern portions of Hispaniola on Saturday. Tropical storm conditions are possible over Jamaica beginning Saturday night. 2. Heavy rainfall from Elsa will move quickly across the Windward and southern Leeward Islands today, including Barbados. Outer rain bands will impact Puerto Rico late today into Saturday, and southern Hispaniola and Jamaica Saturday into Sunday. Flooding and mudslides are possible. 3. There is a risk of wind and rainfall impacts in portions of Cuba, the Turks and Caicos, and the Bahamas through early next week. Interests in these areas should monitor Elsa`s progress and updates to the forecast. 4. There is a risk of storm surge, wind, and rainfall impacts in the Florida Keys and portions of the Florida Peninsula early next week. However, the forecast uncertainty remains larger than usual due to Elsa`s potential interaction with the Greater Antilles this weekend. Interests in Florida should monitor Elsa`s progress and updates to the forecast. FORECAST POSITIONS AND MAX WINDS INIT 02/0900Z 12.7N 58.6W 50 KT 60 MPH 12H 02/1800Z 13.8N 62.4W 55 KT 65 MPH 24H 03/0600Z 15.4N 67.4W 60 KT 70 MPH 36H 03/1800Z 17.1N 71.7W 60 KT 70 MPH 48H 04/0600Z 18.7N 75.2W 60 KT 70 MPH 60H 04/1800Z 20.2N 77.8W 55 KT 65 MPH 72H 05/0600Z 21.7N 79.7W 55 KT 65 MPH 96H 06/0600Z 25.2N 82.2W 55 KT 65 MPH 120H 07/0600Z 29.2N 82.6W 55 KT 65 MPH $$ Forecaster Cangialosi/Berg |
