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Hurricane Sally Discussion Number 19
NWS National Hurricane Center Miami FL AL192020
1000 PM CDT Tue Sep 15 2020
Observations from an Air Force Hurricane Hunter aircraft and
WSR-88D Doppler radar data indicate some strengthening. The eye
has become a little better defined on the radar, and the central
pressure has fallen to 972 mb. The eye has also become evident on
recent IR imagery. Using a blend of flight-level and
SFMR-observed surface winds, along with the Doppler velocities,
gives a current intensity estimate of 75 kt. Given the recent
trends, the official forecast allows for some more intensification
before landfall, which is likely to occur in less than 12 hours.
Rapid weakening will occur after the center moves inland, and the
system should become a remnant low in a couple of days. This is
consistent with the model guidance.
Radar and aircraft center fixes indicate that the motion is now
north-northeastward, or 020/2 kt. Sally should move
north-northeastward, and then northeastward, with a gradual
increase in forward speed, along the northwestern side of a weak
mid-level high pressure area for the next couple of days. Then, as
the system approaches the westerly flow at higher latitudes, the
cyclone should turn toward the east-northeast with a slight further
increase in forward speed until becoming a dissipating remnant low
near the southeast U.S. coast in 2-3 days. The official forecast
is close to the latest corrected dynamical model consensus, HCCA,
prediction.
KEY MESSAGES:
1. Historic, life-threatening flash flooding due to rainfall is
likely through Wednesday along and just inland of the coast from the
Florida Panhandle west of the Apalachicola River to the
Alabama/Mississippi border. Widespread moderate to major river
flooding is forecast across the Florida Panhandle and southern
Alabama. Significant flash and urban flooding, as well as
widespread minor to moderate river flooding, is likely across inland
portions of Mississippi and Alabama, and into Georgia and the
western Carolinas this week.
2. Life-threatening storm surge is expected along portions of the
coastline from Alabama to the western Florida Panhandle, including
Mobile Bay.
3. Hurricane conditions are expected this evening and overnight
within portions of the Hurricane Warning area along the Mississippi
and Alabama coastlines and the western Florida Panhandle.
FORECAST POSITIONS AND MAX WINDS
INIT 16/0300Z 29.8N 87.8W 75 KT 85 MPH
12H 16/1200Z 30.3N 87.5W 80 KT 90 MPH...ON THE COAST
24H 17/0000Z 31.2N 86.8W 40 KT 45 MPH...INLAND
36H 17/1200Z 32.0N 85.7W 30 KT 35 MPH...INLAND
48H 18/0000Z 32.9N 83.9W 25 KT 30 MPH...INLAND
60H 18/1200Z 33.6N 81.5W 20 KT 25 MPH...INLAND
72H 19/0000Z 34.0N 79.0W 20 KT 25 MPH...POST-TROP/REMNT LOW
96H 20/0000Z...DISSIPATED
$$
Forecaster Pasch
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