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Tropical Depression Sally Discussion Number 25
NWS National Hurricane Center Miami FL AL192020
400 AM CDT Thu Sep 17 2020
Although the overall convective cloud and rain shield in satellite
and radar imagery continues to erode, Tropical Depression Sally is
still producing significant rainfall across east-central Alabama
and west-central and central Georgia. Surface observations
and Doppler radar data indicate that Sally has weakened to a 25-kt
depression over southeastern Alabama. Sally will continue to
weaken, and fairly rapidly at that, due to increasing friction and
loss of convection owing to very hostile westerly to southwesterly
vertical wind shear in excess of 40 kt. Sally will likely
degenerate into a remnant low pressure system by tonight or early
Friday, and merge with a frontal system over North Carolina by
Friday evening.
Sally is moving northeastward or 055/10 kt. A northeastward to
east-northeastward motion will continue for the next 36 hours or
so as the cyclone moves ahead of a broad deep-layer trough over the
northeastern United States. The official track forecast is down
the middle of the tightly packed NHC model guidance suite, and lies
close to the previous advisory track and the consensus model HCCA.
This is the last NHC advisory on Sally. Future information on this
system, including the rainfall threat, can be found in Public
Advisories issued by the Weather Prediction Center beginning at
10 AM CDT, under AWIPS header TCPAT3, WMO header WTNT34 KWNH, and
on the web at http://www.wpc.ncep.noaa.gov
KEY MESSAGES:
1. Widespread flooding is expected from central Georgia through
southeastern Virginia. Along the central Gulf Coast, most
widespread moderate to major river flooding from the historic
rainfall event will crest by the weekend, but rivers will remain
elevated well into next week.
FORECAST POSITIONS AND MAX WINDS
INIT 17/0900Z 31.8N 85.7W 25 KT 30 MPH...INLAND
12H 17/1800Z 32.8N 84.2W 25 KT 30 MPH...INLAND
24H 18/0600Z 34.0N 81.3W 20 KT 25 MPH...POST-TROP/REMNT LOW
36H 18/1800Z 35.1N 78.4W 20 KT 25 MPH...POST-TROP/REMNT LOW
48H 19/0600Z...MERGED WITH FRONTAL SYSTEM
$$
Forecaster Stewart
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