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Tropical Storm FRED Forecast Discussion Number 18
2015-09-03 10:46:50| National Hurricane Center (Atlantic)
Issued at 500 AM AST THU SEP 03 2015 000 WTNT41 KNHC 030846 TCDAT1 TROPICAL STORM FRED DISCUSSION NUMBER 18 NWS NATIONAL HURRICANE CENTER MIAMI FL AL062015 500 AM AST THU SEP 03 2015 Fred has made a slight resurgence since the previous advisory with the development of a large cluster of deep convection in the northeastern quadrant, including a narrow band of cloud tops colder than -80C having persisted very near the partly exposed low-level center. The initial intensity has been increased to 40 kt based on a blend of satellite intensity estimates T3.0/45 kt from TAFB, T2.0/30 kt from SAB, and T2.5/35 kt from UW-CIMSS ADT. The initial motion estimate has slowed slightly to 295/07 kt. Otherwise, there remains no change to the forecast track or reasonings mentioned in previous advisory discussions. A shortwave trough currently moving off of the U.S. Mid-Atlantic coast is forecast by the global and regional models to dig east-southeastward into the central Atlantic during the next 5 days, and gradually erode the western portion of the Bermuda-Azores ridge. This will allow Fred to slowly turn northwestward in 48-72 hours, and turn northward at 96 and 120 hours. The NHC guidance is in much better agreement on this developing scenario compared to 24 hours ago. The new official forecast track is essentially just an extension of the previous advisory track and lies close to the consensus models. The GFS and ECMWF models are indicating that more than 30 kt of westerly deep-layer vertical wind shear is affecting Fred. However, this has not kept deep convection from redeveloping near the center, at least for the time being. These strong shear conditions are forecast to persist and even increase during the next 48 hours and, when combined with increasingly drier mid-level air, should induce gradual weakening within the next 12 hours or so. Fred is forecast to weaken to a depression by late tonight or Friday morning, and degenerate into a remnant low by Friday night. By 72 hours and beyond, the remnant low is forecast to reach a more favorable environment of warmer sea surface temperatures, decreasing shear, and increasing moisture, which suggest that there is at least a low probability that regeneration could occur. As a result, the official intensity forecast continues to show a remnant low through 120 h. FORECAST POSITIONS AND MAX WINDS INIT 03/0900Z 20.8N 33.2W 40 KT 45 MPH 12H 03/1800Z 21.4N 34.5W 35 KT 40 MPH 24H 04/0600Z 21.9N 36.1W 30 KT 35 MPH 36H 04/1800Z 22.2N 37.8W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 05/0600Z 22.6N 39.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 06/0600Z 24.0N 41.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 07/0600Z 26.5N 41.7W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 08/0600Z 28.8N 40.3W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Stewart
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