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| #1013296 (Received by flhurricane at: 10:59 AM 22.Aug.2020) TCDAT3 Tropical Storm Laura Discussion Number 11 NWS National Hurricane Center Miami FL AL132020 1100 AM AST Sat Aug 22 2020 Laura is producing considerable deep convection but the cloud pattern remains disorganized. Surface observations indicate that the center is still not well defined, but the San Juan WSR-88D radar shows a mid-level center south of eastern Puerto Rico. The radar also shows heavy rains spreading over that island. The initial intensity estimate remains at 35 kt based on continuity. As noted in previous discussions, the intensity forecast for Laura is dependent on its future track. The official forecast, like the previous one, moves the center over the land masses of Hispaniola and Cuba for the next couple of days which should limit intensification at least through the weekend. After Laura moves into the Gulf of Mexico, warm waters should lead to strengthening and the system is likely to become a hurricane in 3 to 4 days. The official intensity forecast is close to the consensus guidance. At this time the influence of small tropical cyclone Marco, which should move over the northwestern Gulf about a day or two before Laura, is not expected to be significant. This could change in the coming days however. The initial motion estimate remains quite uncertain and is near 280/16 kt. No significant changes are being made to the official track forecast. Laura is likely to move on a generally west-northwestward track on the periphery of a mid-tropospheric high pressure area for the next few days. By day 4, the system should turn northwestward while moving along the southwestern side of the high. The official track forecast is only slightly north of the dynamical model consensus at 36-72 hours and essentially the same as the consensus otherwise. The GFS and its ensemble mean are significantly farther west of the official forecast at days 3 and beyond, which suggests relatively low confidence in the longer-range track of Laura. Key Messages: 1. Tropical storm conditions are expected across portions of the the Virgin Islands and Puerto Rico 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 and could cause mudslides and flash and urban flooding through Sunday, with widespread river flooding possible in Puerto Rico. 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 is forecast to strengthen over the Gulf of Mexico and could bring storm surge, rainfall, and wind impacts to 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 22/1500Z 17.8N 66.8W 35 KT 40 MPH 12H 23/0000Z 18.6N 69.4W 40 KT 45 MPH...INLAND 24H 23/1200Z 19.4N 72.6W 40 KT 45 MPH...INLAND 36H 24/0000Z 20.9N 76.3W 45 KT 50 MPH...INLAND 48H 24/1200Z 22.4N 80.0W 45 KT 50 MPH...INLAND 60H 25/0000Z 23.7N 83.2W 55 KT 65 MPH...OVER WATER 72H 25/1200Z 25.2N 86.2W 65 KT 75 MPH 96H 26/1200Z 27.9N 90.6W 75 KT 85 MPH 120H 27/1200Z 31.6N 92.5W 40 KT 45 MPH...INLAND $$ Forecaster Pasch |