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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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