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Tropical Storm FRED


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Tropical Storm Fred Discussion Number  27
NWS National Hurricane Center Miami FL       AL062021
400 AM CDT Mon Aug 16 2021
 
Earlier reconnaissance aircraft data and satellite imagery indicated 
that Fred's low-level circulation center briefly emerged out from 
underneath the southwestern edge of the convective cloud shield 
between 0200-0400 UTC. The circulation center, however, has recently 
moved back underneath the edge of the main region of convection, 
with a new bust of thunderstorms having developed over or near the 
low-level center. Having said that, Fred still remains a sheared 
tropical cyclone, with Tallahassee NOAA Doppler radar data 
indicating that the upper-level circulation at around 30,000 ft is 
tilted about 40 nmi northeast of the low-level center. The last  
reports from the Air Force Reserve reconnaissance aircraft indicated 
that the central pressure had risen from 999 mb to 1004 mb during 
the time the low-level center was fully exposed southwest of the 
deep convection. However, the pressure has likely fallen again now 
the center is back underneath the convection. An intensity of 45 kt 
is being maintained for this advisory based on the last reliable 
reconnaissance SFMR data of about 45 kt, which corresponds well with 
a T3.0/45 kt Dvorak satellite shear-pattern intensity estimate.
 
Fred is moving northward now, or 355/08 kt. The latest NHC model 
guidance remains in excellent agreement that Fred will continue 
moving in a general northward motion today as the cyclone moves 
through a break in the subtropical ridge that is oriented 
east-to-west across northern Florida. Landfall is expected in the 
western Florida Panhandle region by late afternoon or evening today. 
The track guidance has shifted slightly to the east of the previous 
advisory track, and the new official forecast track has been nudged 
in that direction, but not as far east as the tightly packed 
consensus models owing to the strength of the ridge noted in 16/0000 
UTC upper-air data.
 
Fred is forecast to remain in moderate vertical wind shear 
conditions throughout the 48-h forecast period. However, the shear 
vector is expected to gradually back around from the current 
southwesterly direction to more of a south-southwesterly component 
right up until landfall occurs, which will align more with Fred's 
track direction. This reduction in the effective shear across the 
cyclone should allow for some additional strengthening until 
landfall occurs, with the distinct possibility that Fred could reach 
a peak intensity of 55 kt in 18 hours. After landfall, the 
combination of land interaction and the vertical shear increasing to 
more than 20 kt should result in rapid weakening, with Fred forecast 
to dissipate by 60 hours over the southern Appalachian Mountains. 
The official intensity forecast closely follows a blend of the HCCA 
and IVCN intensity consensus models.
 
Users are reminded not to focus on the exact forecast track of
Fred, since rainfall, storm surge, and wind hazards will extend
over an area well east of the center.
 
KEY MESSAGES:
 
1. Through Tuesday, heavy rainfall may lead to flash, urban, small 
stream, and isolated river flooding impacts across the Southeast.  
By the middle of the week as Fred lifts northward and inland, heavy 
rainfall and flooding will impact the southern and central 
Appalachians, the Piedmont of the Southeast, and the Mid-Atlantic.
 
2. Dangerous storm surge inundation is possible along portions of
the coast of the Florida Panhandle and the Florida Big Bend region,
and a Storm Surge Warning is in effect for this area. Interests in
these areas should follow any advice given by local officials.
 
3. Tropical storm conditions are expected in the tropical storm
warning area beginning later this morning.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  16/0900Z 27.9N  86.0W   45 KT  50 MPH
 12H  16/1800Z 29.1N  86.1W   50 KT  60 MPH
 24H  17/0600Z 31.0N  85.7W   40 KT  45 MPH...INLAND
 36H  17/1800Z 33.1N  85.2W   25 KT  30 MPH...INLAND
 48H  18/0600Z 35.6N  84.2W   20 KT  25 MPH...POST-TROP/INLAND
 60H  18/1800Z...DISSIPATED
 
$$
Forecaster Stewart
 
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