Official Discussion issued by the National Hurricane Center

Helene (AL092024) DATA RELEASED: 9/26/2024 9:00:00 PM UTC

Copy of official data

Hurricane Helene Discussion Number  14
NWS National Hurricane Center Miami FL       AL092024
500 PM EDT Thu Sep 26 2024

Helene has rapidly intensified today while nearing landfall in the
Florida Big Bend.  Doppler radar and aircraft data indicate that the
eyewall is now completely closed and the eye has become more
circular and is clearing out.  The aircraft data also indicated 
that the inner core has contracted significantly today while the
tropical-storm-force winds have expanded.  Based on all of the data,
the initial intensity is set at 110 kt.  The latest minimum pressure
based on the aircraft data is around 951 mb. Tropical-storm-force
winds are occurring across portions of west-central and southwestern
Florida, and conditions are expected to deteriorate rapidly in the
hurricane warning area during the next several hours.  It should be
emphasized that Helene is at the upper bound of hurricanes in
terms of storm size and impacts are and will occur well away 
from the center.

The large hurricane is now accelerating north-northeastward, with
the latest initial motion estimated to be 025/20 kt.  This general
motion is expected to continue, taking the core of the major
hurricane to the Florida Big Bend later this evening.  After
landfall, a turn to the north over Georgia is expected late tonight
and early Friday, followed by a slowdown or a complete stall over
the Tennessee Valley late Friday and Saturday when Helene merges
with a mid- to upper-level low.

The hurricane has intensified by 30 kt since sunrise and given the
conducive environmental conditions and contracting inner core, it
seems likely that Helene will be at or very near category 4 strength
when it makes landfall in the Florida Big Bend this evening.
The fast forward speed when Helene moves inland will result in a
far inland penetration of strong winds over parts of the
southeastern United States, including strong gusts over the higher
terrain of the southern Appalachians.  Accordingly, a
higher-than-normal gust factor is indicated in the official forecast
while Helene is inland.

KEY MESSAGES:

1. A catastrophic and deadly storm surge will occur along portions 
of the Florida Big Bend coast, where inundation could reach as high 
as 20 feet above ground level, along with destructive waves.  If 
you live in this area and were told to evacuate by local officials, 
your opportunity to do so is almost over.  There is also a danger 
of life-threatening storm surge along the remainder of the west 
coast of the Florida Peninsula.  

2. Potentially catastrophic hurricane-force winds are expected 
within the eyewall of Helene and will spread inland over portions 
of northern Florida and southern Georgia when Helene makes landfall 
in the Florida Big Bend region this evening.  Persons in these 
areas should be prepared to take shelter in the interior portion of 
a well-built structure and remain sheltered until after hazardous 
conditions pass. You may need to remain sheltered after the storm 
due to downed trees and power lines, as well as flooding, in the 
area.

3. Damaging wind gusts will penetrate well inland over portions of 
Georgia and the Carolinas  tonight, particularly over the higher 
terrain of the southern Appalachians. Residents in these areas 
should be prepared for the possibility of long-duration power 
outages.  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.

4. Catastrophic and life-threatening flash and urban flooding, 
including numerous significant landslides, is expected across 
portions of the southern Appalachians through Friday. Considerable 
to locally catastrophic flash and urban flooding is likely for 
northwestern and northern Florida and the Southeast through Friday. 
Widespread significant river flooding and isolated major river 
flooding are likely.


FORECAST POSITIONS AND MAX WINDS

INIT  26/2100Z 27.9N  84.6W  110 KT 125 MPH
12H  27/0600Z 31.5N  83.7W   90 KT 105 MPH...INLAND
24H  27/1800Z 35.8N  85.0W   40 KT  45 MPH...POST-TROP/EXTRATROP
36H  28/0600Z 37.0N  86.5W   30 KT  35 MPH...POST-TROP/EXTRATROP
48H  28/1800Z 37.1N  87.0W   25 KT  30 MPH...POST-TROP/EXTRATROP
60H  29/0600Z 37.1N  87.3W   20 KT  25 MPH...POST-TROP/EXTRATROP
72H  29/1800Z...DISSIPATED

$$
Forecaster Cangialosi