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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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