Hurricane Idalia Discussion Number  14
NWS National Hurricane Center Miami FL       AL102023
1100 PM EDT Tue Aug 29 2023

Satellite and NWS radar imagery show that Idalia is becoming 
increasingly more organized.  The eye on the Tampa WSR-88D is 
becoming better defined and the cloud pattern on GOES 16 imagery 
consists of a growing Central Dense Overcast with a strong 
convective band over the eastern semicircle of the circulation.  
Reconnaissance aircraft measurements show that the central pressure 
is steadily falling and is now around 958 mb.  Flight-level and 
SFMR-observed winds along with Doppler velocity data from the 
aircraft support an intensity of 95 kt for this advisory.

Idalia is now moving faster toward the north or slightly east of 
north with a motion estimate of 010/16 kt. The hurricane is moving 
between a mid-level trough over the northwestern Gulf of Mexico and 
ridge over the Bahamas and Greater Antilles.  The system is expected 
to turn north-northeastward within the next 12 hours, make landfall 
along the northeastern Gulf coast, and then move northeastward to 
eastward on the southern side of a mid-level trough moving off the 
northeast U.S. coast.  The 12-hour track forecast point for this 
advisory has been nudged a bit westward, a little west of the model 
consensus, but close to the latest GFS and ECMWF solutions.  It 
should be noted that some credible models, i.e. the HAFS-A and 
HAFS-B predictions, are even a little father west.

After landfall, Idalia is expected to move near or along the coast 
of Georgia and the Carolinas in 24-36 hours.  Uncertainty in the 
track forecast beyond 48 hours remains quite large, with some of 
the global models turning Idalia southward, while some of the 
regional hurricane models show the storm moving out to sea.  Given 
the uncertainties, the official track forecast shows a slow 
southeastward motion in 4 to 5 days.

Based on the current strengthening trend and the favorable 
thermodynamic and oceanic conditions, significant strengthening 
seems likely up to landfall.  The new official intensity forecast 
calls for Idalia to reach category 4 strength at landfall.  This is 
fairly close to the HAFS And HWRF regional hurricane model 
simulations.  After the center moves back over the Atlantic, 
significant restrengthening is not anticipated at this time due to 
the expectation of strong vertical west-southwesterly vertical wind 
shear.

Dangerous winds are likely to spread well inland near the path of 
Idalia due to its relatively fast forward motion.


KEY MESSAGES:

1. Catastrophic impacts from storm surge inundation of 12 to 16 feet 
above ground level and destructive waves are expected somewhere 
between the Wakulla/Jefferson County line 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 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. Damaging hurricane-force
winds are possible in portions of eastern Georgia and southeastern
South Carolina where Hurricane Watches are in effect.

3. Areas of flash, urban, and moderate river flooding, with locally
considerable impacts, are expected across the Florida Big Bend,
central Georgia and South Carolina, through eastern North Carolina
into Thursday.


FORECAST POSITIONS AND MAX WINDS

INIT  30/0300Z 27.7N  84.5W   95 KT 110 MPH
12H  30/1200Z 30.0N  83.9W  115 KT 130 MPH...ON COAST
24H  31/0000Z 32.3N  81.3W   70 KT  80 MPH...INLAND
36H  31/1200Z 33.5N  78.6W   50 KT  60 MPH...OVER WATER
48H  01/0000Z 33.8N  75.0W   50 KT  60 MPH
60H  01/1200Z 33.5N  72.5W   50 KT  60 MPH
72H  02/0000Z 32.9N  71.0W   45 KT  50 MPH
96H  03/0000Z 32.0N  69.4W   45 KT  50 MPH
120H  04/0000Z 31.0N  68.4W   45 KT  50 MPH

$$
Forecaster Pasch