Hurricane Idalia Forecast Discussion Number 12

By | August 29, 2023

WTNT45 KNHC 291454

Hurricane Idalia Discussion Number  12
NWS National Hurricane Center Miami FL       AL102023
1100 AM EDT Tue Aug 29 2023

WSR-88D radar data from Key West shows that Idalia's eye is
becoming better defined at an elevation of 30,000 feet, although an
eye has not yet become apparent in visible satellite imagery.  A
NOAA Hurricane Hunter aircraft reported a closed eye 20-25 n mi in
diameter, SFMR winds as high as 70 kt, and a central pressure down
to 976 mb.  This pressure, and assuming some undersampling of the
SFMR, supports an initial intensity of 75 kt.

Idalia is moving just east of due north, or 005/12 kt, between a
mid-level trough over the Gulf of Mexico and subtropical ridging
over the Greater Antilles.  A faster motion toward the north or
north-northeast is expected while Idalia approaches the Florida
coast through Wednesday morning.  Confidence is increasing that
Idalia will reach the coast of Florida adjacent to Apalachee Bay
Wednesday morning, with all of the reliable deterministic track
models honed in on that area.  Track spread remains low during
Idalia's expected turn toward the northeast and east-northeast in
48-60 hours, bringing the storm's center near or along the coast of
the Carolinas.  On days 3 through 5, there is significant
uncertainty on whether Idalia will turn out to sea (as shown by the
COAMPS-TC and HAFS models) or turn southward (as suggested by the
global models).  For now, the official forecast shows a slow motion
at the end of the forecast period until the scenario becomes

Idalia is currently over a maximum of oceanic heat content
associated with the Loop Current, and water temperatures remain
30-31 degrees Celsius along the forecast path up until landfall.
Vertical shear is also expected to be low for the next 18-24 hours,
and these conditions are expected to foster rapid intensification
before Idalia reaches the coast of Florida.  The 06 UTC runs of all
4 regional hurricane models (HAFS-A, HAFS-B, HWRF, and HMON) show
Idalia potentially reaching an intensity of 110-120 kt in 24 hours,
and as a result, the new NHC intensity forecast indicates a peak
intensity of 110 kt just before landfall.  Weakening is forecast
while the center of Idalia moves over land, but the system is
expected to be a tropical storm while it moves near or along the
coasts of Georgia and the Carolinas through Thursday.


1. Catastrophic impacts from storm surge inundation of 10 to 15 feet
above ground level and destructive waves are expected somewhere
between Aucilla River and Yankeetown, Florida. Life-threatening
storm surge inundation is likely elsewhere along portions of the
Florida Gulf Coast where a Storm Surge Warning is in effect.
Residents in these areas should follow any advice or evacuation
orders given by local officials.

2. There is the potential for destructive life-threatening winds
where the core of Idalia moves onshore in the Big Bend region of
Florida, with hurricane conditions expected elsewhere in portions of
the Hurricane Warning area along the Florida Gulf Coast. Strong
winds will also spread inland across portions of northern Florida
and southern Georgia near the track of the center of Idalia where
Hurricane Warnings are in effect. Residents in these areas should be
prepared for long-duration power outages.

3. Areas of flash and urban flooding, some of which may be locally
significant, are expected across portions of the west coast of
Florida, the Florida Panhandle, and southern Georgia Tuesday into
Wednesday, spreading into portions of the eastern Carolinas
Wednesday into Thursday.

4. Heavy rainfall from Tropical Storm Idalia is expected across
portions western Cuba and may produce areas of flash and urban
flooding as well as landslides.


INIT  29/1500Z 24.6N  84.8W   75 KT  85 MPH
 12H  30/0000Z 26.5N  84.6W   90 KT 105 MPH
 24H  30/1200Z 29.3N  83.7W  110 KT 125 MPH
 36H  31/0000Z 31.8N  81.7W   55 KT  65 MPH...INLAND
 48H  31/1200Z 33.5N  78.8W   45 KT  50 MPH...OVER WATER
 60H  01/0000Z 34.1N  75.6W   45 KT  50 MPH
 72H  01/1200Z 33.8N  73.0W   45 KT  50 MPH
 96H  02/1200Z 32.5N  70.2W   45 KT  50 MPH
120H  03/1200Z 32.0N  68.8W   45 KT  50 MPH

Forecaster Berg

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