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| #1056967 (Received by flhurricane at: 5:12 AM 15.Aug.2021) TCDAT1 Remnants Of Fred Discussion Number 23 NWS National Hurricane Center Miami FL AL062021 500 AM EDT Sun Aug 15 2021 The remnants of Fred have been undergoing some noticeable changes early this morning, with one of those features being a curved band of deep convection having developed in the northeastern quadrant of the larger cyclonic envelope. A low-level jet (925-850 mb) was noted in the 0000 UTC upper-air air data and in the Key West VAD wind profile radar data late last night and early this morning. That speed maximum produced 2-hours worth of 34-kt and higher 10-meter winds at the Sand Key (SANF1) C-MAN station south of Key West, and that is the basis for the increasing the intensity to 35 kt for this advisory. That speed maximum is also likely responsible for the large increase in convection north of the Dry Tortugas, which also has helped to spin up a small mesovortex that passed over buoy 42026 between 0500-0600 UTC, causing the pressure to decrease 3.6 mb in one hour. That small-scale feature is moving westward and could become the the low-level center farther to the north of the current alleged center within the next few hours. The initial motion estimate is an uncertain 330/07 kt. The system is expected to move north-northwestward or northwestward today and tonight through a narrow weakness in the subtropical ridge located between 85W-88W longitude based on 0000Z upper-air data. The system is forecast to turn northward on Monday as it nears the northern Gulf of coast and comes under the influence of a mid- to upper-level trough forecast to drop southward over the western Gulf of Mexico. The new NHC track forecast had to be shifted farther to the east of the previous advisory, and subsequent forecast tracks may have to be shifted even further east if a new center develops farther to the north or northeast as per what recent satellite and buoy data suggest. The official forecasts track lies a little to the left of the tightly packed consensus track models. Upper-level winds are expected to remain marginally conducive for strengthening due to at least some modest southwesterly wind shear affecting the cyclone for the next 48 hours. After landfall, Fred is forecast to weaken rapidly and the global models indicate the circulation should dissipate by around 96 hours. KEY MESSAGES: 1. Today through Monday, heavy rainfall could lead to areal, urban, and small stream flooding impacts, and cause new and renewed river flooding across southern Florida, the Big Bend, and Panhandle. From Monday onward, heavy rain and flood impacts could extend into other portions of the Southeast and into the southern and central Appalachians and Piedmont as Fred interacts with a front in the area. 2. Fred is forecast to regenerate as a tropical cyclone over the Gulf of Mexico later today, and bring a risk of tropical storm conditions to portions of the northern Gulf coast, especially from coastal Mississippi to the Florida Panhandle beginning Monday night. A Tropical Storm Warning will likely be required for a portion of this area later this morning. FORECAST POSITIONS AND MAX WINDS INIT 15/0900Z 24.4N 84.6W 35 KT 40 MPH 12H 15/1800Z 25.5N 85.6W 35 KT 40 MPH...TROPICAL CYCLONE 24H 16/0600Z 27.0N 86.6W 40 KT 45 MPH 36H 16/1800Z 28.5N 87.1W 45 KT 50 MPH 48H 17/0600Z 30.3N 87.1W 45 KT 50 MPH 60H 17/1800Z 32.5N 86.8W 30 KT 35 MPH...INLAND 72H 18/0600Z 35.0N 85.8W 20 KT 25 MPH...INLAND 96H 19/0600Z...DISSIPATED $$ Forecaster Stewart |