Tropical Storm Helene Forecast Discussion

000
WTNT44 KNHC 271436
TCDAT4

Tropical Storm Helene Discussion Number  17
NWS National Hurricane Center Miami FL       AL092024
1100 AM EDT Fri Sep 27 2024

Helene has been racing northward and the low-level center is now
located over the southern Appalachians.  Strong bands of heavy rain
and very gusty winds continue off and along the South Carolina
coast.  In addition, wind gusts to around hurricane force have been
occurring this morning in portions of northeastern Georgia and the
western portions of the Carolinas, especially in areas of higher
terrain.  The initial intensity is set at 40 kt, and these sustained
winds are likely occurring off the south Carolina coast and over
the Appalachians.  The main hazard is the very heavy rainfall 
ongoing over portions of the southeastern U.S., which is 
causing historic and life-threatening flooding.

Helene is expected to move slower to the northwest later today and 
then stall over the Tennessee Valley tonight and through the weekend 
as it merges with a mid- to upper-level low.  This merger will also 
lead to extratropical transition, which is expected to occur later 
today.  The expected slow motion could result in significant 
flooding over the Ohio and Tennessee Valleys, and over the southern 
Appalachians through the weekend.

KEY MESSAGES:

1. Historic, catastrophic and life-threatening flash and urban 
flooding, including numerous significant landslides, will continue 
across portions of the Southern Appalachians through this evening. 
Widespread significant river flooding is ongoing, some of which will 
be major to record breaking.

2. Damaging wind gusts will continue over portions of Georgia, the
Carolinas, Tennessee, and Kentucky today, particularly over the
higher terrain of the southern Appalachians.

3. There is a possibility of long-duration power outages in
portions of the southeast U.S.  If you use a generator after the
storm, be sure it is placed outside at least 20 feet away from
doors, windows, and garages to avoid deadly carbon monoxide
poisoning.


FORECAST POSITIONS AND MAX WINDS

INIT  27/1500Z 35.1N  83.8W   40 KT  45 MPH
 12H  28/0000Z 37.3N  85.6W   30 KT  35 MPH...POST-TROP/EXTRATROP
 24H  28/1200Z 37.5N  86.5W   25 KT  30 MPH...POST-TROP/EXTRATROP
 36H  29/0000Z 37.5N  86.4W   20 KT  25 MPH...POST-TROP/EXTRATROP
 48H  29/1200Z 37.5N  86.1W   20 KT  25 MPH...POST-TROP/EXTRATROP
 60H  30/0000Z 37.6N  85.7W   20 KT  25 MPH...POST-TROP/EXTRATROP
 72H  30/1200Z...DISSIPATED

$$
Forecaster Cangialosi/Rosado