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Tropical Depression Fred Forecast Discussion Number 16
2021-08-13 16:51:17| National Hurricane Center (Atlantic)
Issued at 1100 AM EDT Fri Aug 13 2021 000 WTNT41 KNHC 131451 TCDAT1 Tropical Depression Fred Discussion Number 16 NWS National Hurricane Center Miami FL AL062021 1100 AM EDT Fri Aug 13 2021 Fred remains disorganized this morning. The low-level center, which is currently over the barrier islands of the north coast of Cuba, is exposed to the northwest of the main convective mass due to moderate southwesterly vertical shear. Reports from Air Force Reserve and NOAA Hurricane hunter aircraft show winds of 25-30 kt to the northeast of the center, so the initial intensity remains 30 kt. The central pressure is 1013 mb based on a combination of aircraft data and surface observations. The center has jogged a bit to the left during the past several hours, which has brought it to the Cuban coast. The longer-term initial motion is 295/10. The cyclone should continue west-northwestward for the next 12-24 h, followed by a turn toward the northwest as Fred approaches the western periphery of the subtropical ridge. This motion should take the center along the northern coast of Cuba today, near the Florida Keys and the southwestern coast of Florida on Saturday, and near or over the coast of the Florida Panhandle Sunday night or Monday. After that, a northward turn is expected as Fred moves into a weakness in the ridge over the southeastern United States. With both the initial position and the track guidance shifting westward since the last advisory, the new forecast track is also nudged a little to the west. The new track is east of the consensus models, especially from 24-60 h, and thus some additional adjustments could occur later today if the current model trends continue. Fred is continuing to experience about 20 kt of westerly or southwesterly vertical wind shear, and these conditions should continue for at least another 24 hours. Between that and land interaction, the intensity forecast calls for only modest strengthening during this time. After that, there is still relatively poor agreement on how much shear Fred will experience as it crosses the eastern Gulf of Mexico, with the ECMWF and the UKMET forecasting less shear than the GFS and CMC global models. Due to the uncertainty, the intensity forecast will keep the previous peak intensity of 45 kt. However, the intensity guidance during this period has trended a little higher, and the 45 kt peak is now a little below the upper edge of the guidance. It should be noted that much of the Florida peninsula is expected to be on the east side of Fred, which is where the heaviest rains, strongest winds, and a chance of tornadoes will be. KEY MESSAGES: 1. Today through Monday, heavy rainfall could lead to areal, urban, small stream, and exacerbated river flooding across southern and central Florida into the Big Bend. From Sunday 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 that area. 2. Tropical storm conditions are expected in portions of the Florida Keys on Saturday, where a Tropical Storm Warning is in effect. 3. Tropical storm conditions are possible late Saturday and early Sunday across portions of the west coast of Florida in the Tropical Storm Watch area. The risk of tropical storm conditions will spread northward along the Florida west coast and to the Florida Panhandle Sunday and Monday. FORECAST POSITIONS AND MAX WINDS INIT 13/1500Z 22.3N 78.4W 30 KT 35 MPH...NEAR COAST OF CUBA 12H 14/0000Z 23.0N 79.7W 30 KT 35 MPH 24H 14/1200Z 24.2N 81.3W 35 KT 40 MPH 36H 15/0000Z 25.6N 82.5W 35 KT 40 MPH 48H 15/1200Z 27.2N 83.6W 40 KT 45 MPH 60H 16/0000Z 28.7N 84.6W 45 KT 50 MPH 72H 16/1200Z 30.2N 85.4W 35 KT 40 MPH...INLAND 96H 17/1200Z 33.0N 86.5W 25 KT 30 MPH...INLAND 120H 18/1200Z 36.5N 86.5W 20 KT 25 MPH...POST-TROP/INLAND $$ Forecaster Beven
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