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Tropical Depression Fred Discussion Number  14
NWS National Hurricane Center Miami FL       AL062021
1100 PM EDT Thu Aug 12 2021
 
Data from an Air Force Reserve reconnaissance aircraft this indicate
that Fred's inner-core wind field Fred remains poorly organized.
Also, data from a NOAA reconnaissance aircraft suggests that the
650-mb mid-level circulation center is titled at least 40 nmi to
the east of the low-level center. The maximum 925-mb flight-level
wind measured thus far has been 43 kt and the highest reliable SFMR
surface wind speed sampled has been 33 kt. A blend of these data
support maintaining a solid 30-kt intensity for this advisory, but
Fred is right on the cusp of regaining tropical storm status.
 
Fred has slowed down some more, with the initial motion estimate an 
uncertain 295/08 kt. The uncertainty in Fred's forward motion is 
related to the speed due to the low-level center jumping around 
every time a small convective tower develops within the larger 
cloud mass. However, the general motion of the wind field and the 
associated pressure envelope is toward the west-northwest or 295 
degrees. Otherwise, there is no significant changes to the previous 
track forecast or reasoning. Fred is expected to continue moving 
west-northwestward along the southwestern periphery of a deep-layer 
for the next 36 hours or so, followed by a northwestward motion near 
or just offshore the Florida west coast in the 48-to-72-hour period. 
On days 4 and 5, a slower northward motion is forecast as Fred moves 
into a developing weakness in the ridge. The latest track guidance 
has become more divergent, with the GFS model dissipating and then 
redeveloping Fred over south Florida in about 48 hours, with the 
other models taking a weakening cyclone more westward. The exception 
is the westward-trending ECMWF model, which moves Fred along the 
Florida west coast. The new NHC track forecast was nudged slightly 
to the east or right of the previous advisory track after 24 hours, 
but lies to the left of the ECMWF model and between the NOAA-HCCA 
and TVCA consensus track models.
 
Fred is forecast to remain under the influence of westerly to 
southwesterly vertical wind shear for the next 72 hours. It is the 
magnitude of the shear that is in question. The GFS maintains 15-20 
kt of shear for the next three days, whereas the ECMWF model 
decreases the shear to around 10 kt in the 24-to-60-hour period, 
with the latter scenario favoring some strengthening if Fred doesn't 
interact too much with the Florida peninsula. Due to the uncertainty 
in the amount of shear and land interaction that will be 
encountered, latest official intensity forecast remains similar to 
the previous advisory and a blend of the HCCA and TVCA consensus 
model intensity forecasts. 
 
KEY MESSAGES:
 
1. From Friday into Monday, heavy rainfall could lead to areal, 
urban, small stream, and exacerbated river flooding, across southern 
and central Florida, and into the Big Bend of Florida. By early next 
week, heavy rain and flood impacts could extend into other portions 
of the Southeast and into the southern and central Appalachians and 
Piedmont.
 
2. Tropical storm conditions are possible beginning Friday night and
Saturday in the Florida Keys and portions of southern Florida, where
a Tropical Storm Watch is in effect.  The risk of tropical storm
conditions will spread northward along portions of the Florida west
coast and to the Florida Panhandle Saturday night through Monday.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  13/0300Z 21.5N  75.6W   30 KT  35 MPH
 12H  13/1200Z 22.2N  77.1W   35 KT  40 MPH
 24H  14/0000Z 23.0N  79.0W   35 KT  40 MPH
 36H  14/1200Z 24.2N  80.6W   40 KT  45 MPH
 48H  15/0000Z 25.5N  82.1W   40 KT  45 MPH
 60H  15/1200Z 27.2N  83.1W   45 KT  50 MPH
 72H  16/0000Z 29.1N  84.2W   45 KT  50 MPH
 96H  17/0000Z 31.8N  85.6W   35 KT  40 MPH...INLAND
120H  18/0000Z 34.4N  85.5W   25 KT  30 MPH...INLAND
 
$$
Forecaster Stewart
 
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