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| #1013260 (Received by flhurricane at: 5:18 AM 22.Aug.2020) TCDAT3 Tropical Storm Laura Discussion Number 10 NWS National Hurricane Center Miami FL AL132020 500 AM AST Sat Aug 22 2020 Surface observations and Doppler radar data from Puerto Rico indicate that the center of Laura is currently over the Virgin Islands, eastern Puerto Rico, and the adjacent Caribbean waters. Overall, the system has become a little better organized since the last advisory, with strong convection forming not far from the center to the east and southeast and a somewhat better defined circulation. However, the central area of light winds is quite large, and there is evidence of several vorticity centers rotating around the mean storm center. Earlier scatterometer data suggested that the maximum winds had decreased to 35 kt, and that is the initial intensity for this advisory. The initial motion is a somewhat uncertain 280/18. There is no change in the track forecast philosophy, as a subtropical ridge over the central and western Atlantic is expected to expand westward, causing Laura to move quickly west-northwestward for the next 3 days or so. After that, the storm should turn northwestward toward the western edge of the ridge over the northern Gulf coast. While the dynamical models are in good agreement with the general scenario, there is an unusual amount of cross track spread. The track guidance is spread from the Florida Keys to the western end of Cuba as the storm enters the Gulf of Mexico, and the models have potential landfall locations along the Gulf coast from the Florida Panhandle to the middle Texas coast. One complicating factor is the potential for interaction with Tropical Storm Marco, although at this time the model guidance suggests the storms will stay far enough apart to prevent direct interaction. The new forecast track is similar to the previous track through 72 hr, then it is shifted a bit to the west after that time. The new track lies near the various consensus models. Laura is moving into an environment of light shear, and combined with the somewhat improved organization it suggests the storm should strengthen. However, the forecast track takes the center over Hispaniola and then down the length of Cuba, which should at least slow any intensification. This is reflected in the new intensity forecast which shows slow strengthening. Over the Gulf of Mexico, warm water and a likely favorable shear environment should allow Laura to become a hurricane, a scenario now supported by much of the guidance. Key Messages: 1. Tropical storm conditions are expected across portions of the northern Leeward Islands, the Virgin Islands, and Puerto Rico through today. Tropical storm conditions are also expected along the northern coasts of the Dominican Republic and Haiti, and the Turks and Caicos and southeastern Bahamas Saturday into Sunday. Heavy rainfall is likely across these areas beginning and could cause mudslides and flash and urban flooding through Sunday. 2. Tropical storm conditions are possible over portions of the central Bahamas Sunday night, as well as portions of eastern and central Cuba Sunday and Sunday night. 3. The details of the long-range track and intensity forecasts remain more uncertain than usual since Laura is forecast to move near or over portions of the Greater Antilles through Monday. However, Laura could bring storm surge, rainfall, and wind impacts to portions of Cuba, the Bahamas, and Florida early next week and the northern U.S. Gulf Coast by the middle of next week. Interests there should monitor the progress of Laura and updates to the forecast during the next few days. FORECAST POSITIONS AND MAX WINDS INIT 22/0900Z 17.6N 65.5W 35 KT 40 MPH 12H 22/1800Z 18.2N 67.7W 40 KT 45 MPH 24H 23/0600Z 19.1N 71.0W 40 KT 45 MPH...INLAND 36H 23/1800Z 20.3N 74.6W 45 KT 50 MPH...INLAND 48H 24/0600Z 21.6N 78.3W 45 KT 50 MPH...INLAND 60H 24/1800Z 23.1N 81.8W 45 KT 50 MPH...INLAND 72H 25/0600Z 24.6N 84.7W 55 KT 65 MPH...OVER WATER 96H 26/0600Z 27.5N 89.5W 75 KT 85 MPH...OVER WATER 120H 27/0600Z 31.0N 92.0W 55 KT 65 MPH...OVER WATER $$ Forecaster Beven |