Hurricane Helene Discussion Number  15
NWS National Hurricane Center Miami FL       AL092024
1100 PM EDT Thu Sep 26 2024

The hurricane is about to make landfall in the Florida Big Bend
region.  Timely observations from Air Force and NOAA Hurricane
Hunter aircraft showed that Helene continued to strengthen rapidly
to Category 4 status before it approached the coast, with the
central pressure falling at about 3 mb per hour since this
afternoon.  Peak 700 mb flight-level winds from the aircraft were
136 kt, corresponding to an intensity of about 120 kt, which might
be a bit conservative.  Radar and satellite images show numerous
mesocyclones rotating around the eyewall.

The large hurricane continues moving rapidly north-northeastward
with the latest initial motion estimated to be 015/21 kt.  A
generally northward track is expected overnight, taking the center
from southern to northern Georgia through early Friday morning.
Later on Friday and Saturday, Helene should slow down considerably
while it interacts with a mid-level low to its northwest and west.
The weakening system is likely to become nearly stationary in 48-60
hours.  The official track forecast follows the dynamical model
consensus.

Although the system will weaken as it moves over land, the fast
forward speed of Helene during the next 12 hours or so will result
in a far inland penetration of strong winds over parts of the
southeastern United States, particularly over Georgia, 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 is occurring along portions
of the Florida Big Bend coast, where inundation could reach as high
as 20 feet above ground level, along with destructive waves.  There
is also a danger of life-threatening storm surge along the remainder
of the west coast of the Florida Peninsula.

2. Catastrophic hurricane-force winds are occurring near the coast
within the eyewall of Helene and will spread inland over portions
of northern Florida and southern Georgia.

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  27/0300Z 29.9N  83.9W  120 KT 140 MPH
12H  27/1200Z 33.9N  84.0W   55 KT  65 MPH...INLAND
24H  28/0000Z 36.9N  86.2W   30 KT  35 MPH...POST-TROP/EXTRATROP
36H  28/1200Z 36.8N  87.5W   25 KT  30 MPH...POST-TROP/EXTRATROP
48H  29/0000Z 36.9N  86.9W   20 KT  25 MPH...POST-TROP/EXTRATROP
60H  29/1200Z 37.1N  86.4W   20 KT  25 MPH...POST-TROP/EXTRATROP
72H  30/0000Z...DISSIPATED

$$
Forecaster Pasch