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Tropical Storm Fred Forecast Discussion Number 8
2021-08-11 16:56:34| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Wed Aug 11 2021 000 WTNT41 KNHC 111456 TCDAT1 Tropical Storm Fred Discussion Number 8 NWS National Hurricane Center Miami FL AL062021 1100 AM AST Wed Aug 11 2021 Morning satellite imagery and reports from a NOAA Hurricane Hunter aircraft indicate that the circulation of Fred has become better defined south of the eastern Dominican Republic. The NOAA plane reported maximum flight-level winds of 40-45 kt, and SFMR winds of up to 50 kt, although these were measured near the coast and the reliability is unknown. The central pressure is near 1006 mb. Based on these data and a dropsonde northeast of the center, the initial intensity is increased to 40 kt. The low-level center is partly exposed near the western edge of the convection, which has decreased in coverage since yesterday. The center has been moving more westward for the past few hours. However, the longer term motion is 290/14. There is no change in the track forecast philosophy since the previous advisory. Fred should continue moving generally west-northwestward for the next 72 h or so, followed by a turn toward the northwest as the cyclone nears the western periphery of the ridge. The new forecast track is little changed from the previous advisory and lies near the various consensus models. However, some adjustments to the track may be necessary as the center interacts with the mountains of Hispaniola during the next 12-24 hours. Fred is now in an environment of 15-20 kt of westerly vertical shear produced in part by an upper-level trough near the Florida Peninsula, and the global models suggests that moderate shear should persist for at least the next 48-60 h. This, combined with land interaction, should cause Fred to weaken as it crosses Hispaniola, and then at best slowly re-intensify after it emerges over the water. After that time, the global models suggest the trough should weaken as a large upper-level anticyclone forms near or just southeast of Fred. This evolution could let the shear decrease a little and allow a little more strengthening, particularly when Fred is over the Gulf of Mexico. The new intensity forecast is similar to the previous forecast and follows the overall trend of the intensity guidance. KEY MESSAGES: 1. Tropical storm conditions are spreading across portions of the Dominican Republic. Tropical storm conditions are possible in northern Haiti and the southeastern Bahamas by late today, and in portions of Cuba by tonight. 2. Heavy rainfall could lead to flash, urban, and small stream flooding, along with possible rapid river rises and the potential for mudslides in the Dominican Republic. Heavy rainfall could lead to flash, urban, and small stream flooding, along with possible rapid river rises across southern Florida. 3. There is a risk of wind and rainfall impacts elsewhere in portions of Hispaniola, the Bahamas, and Cuba during the next few days, although the forecast is more uncertain than usual since Fred is forecast to interact with Hispaniola today and tonight. Interests in these areas should monitor Fred's progress and updates to the forecast. 4. There is an increasing risk of wind and rainfall impacts in Florida beginning Friday night or early Saturday in the Keys and spreading northward through portions of the Peninsula and the Panhandle Saturday through Monday. Interests throughout Florida should monitor Fred's progress and check updates to the forecast. FORECAST POSITIONS AND MAX WINDS INIT 11/1500Z 18.2N 69.7W 40 KT 45 MPH 12H 12/0000Z 19.2N 71.4W 30 KT 35 MPH...INLAND 24H 12/1200Z 20.3N 73.7W 30 KT 35 MPH...OVER WATER 36H 13/0000Z 21.4N 76.0W 35 KT 40 MPH 48H 13/1200Z 22.3N 78.1W 35 KT 40 MPH 60H 14/0000Z 23.3N 79.9W 40 KT 45 MPH 72H 14/1200Z 24.6N 81.4W 40 KT 45 MPH 96H 15/1200Z 27.5N 83.5W 50 KT 60 MPH 120H 16/1200Z 30.5N 85.5W 55 KT 65 MPH...INLAND $$ Forecaster Beven
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