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Tropical Depression Fred Forecast Discussion Number 18
2021-08-14 04:51:25| National Hurricane Center (Atlantic)
Issued at 1100 PM EDT Fri Aug 13 2021 239 WTNT41 KNHC 140251 TCDAT1 Tropical Depression Fred Discussion Number 18 NWS National Hurricane Center Miami FL AL062021 1100 PM EDT Fri Aug 13 2021 Interaction with land and southwesterly shear has continued to take a toll on Fred this evening. It is very difficult to determine in infrared satellite imagery and recent surface observations from Cuba if a closed circulation still exists, however the system is maintained as a tropical depression for now. Scatterometer data, which should arrive very soon, and reconnaissance aircraft observations on Saturday morning should provide additional information on the system's intensity and structure. The system still appears to be moving moving westward or 280/11 kt. There has been no change to the track forecast reasoning from the previous advisory. The cyclone is approaching the western periphery of a subtropical ridge extending over the western Atlantic, and Fred should turn west-northwestward overnight, and then northwestward on Saturday. The track guidance has again shifted westward, but the shift is not as large as was noted on the previous cycle. The NHC track forecast has been adjusted to the left, closer to the consensus aids, but it still remains to the east of those models. Some additional westward adjustments in subsequent forecasts may be required. As mentioned above, land interaction and southwesterly vertical will limit any attempt of re-organization overnight, however the system is expected to move off the northern coast of Cuba Saturday morning and the global model guidance suggests that a center re-formation could occur over the western portion of the Straits of Florida. The center re-formation shown by the guidance appears to be aided by an area of upper-level diffluent flow to the southeast of an upper-level trough currently located over the eastern Gulf of Mexico. Although only a little strengthening is indicated in the official forecast through 36 hours, the environment could become a little more conducive on Sunday, and the NHC wind speed forecast again calls for gradual strengthening while Fred moves northwestward over the eastern Gulf. The updated intensity forecast is unchanged from the previous advisory and is a blend of the statistical guidance and the HCCA model. The intensity forecast continues to be of lower-than-normal confidence given the current disorganized structure of the system. KEY MESSAGES: 1. Tonight through Monday, heavy rainfall could lead to areal, urban, and small stream flooding impacts, and cause new and renewed 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 the area. 2. Tropical storm conditions are expected in portions of the Lower Florida Keys on Saturday, where a Tropical Storm Warning is in effect. 3. There is a risk of tropical storm conditions in the Florida Panhandle beginning on Monday. Watches may be required for a portion of this area on Saturday. FORECAST POSITIONS AND MAX WINDS INIT 14/0300Z 22.7N 80.6W 30 KT 35 MPH 12H 14/1200Z 23.4N 81.9W 30 KT 35 MPH...OVER WATER 24H 15/0000Z 24.8N 83.6W 35 KT 40 MPH 36H 15/1200Z 26.3N 85.0W 35 KT 40 MPH 48H 16/0000Z 27.8N 86.0W 40 KT 45 MPH 60H 16/1200Z 29.2N 86.6W 45 KT 50 MPH 72H 17/0000Z 30.6N 86.8W 50 KT 60 MPH...INLAND 96H 18/0000Z 34.0N 86.5W 25 KT 30 MPH...INLAND 120H 19/0000Z 37.5N 84.0W 20 KT 25 MPH...POST-TROP/INLAND $$ Forecaster Brown
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