Hurricane Idalia Forecast Discussion Number 15

By | August 30, 2023

WTNT45 KNHC 300857

Hurricane Idalia Discussion Number  15
NWS National Hurricane Center Miami FL       AL102023
500 AM EDT Wed Aug 30 2023

Idalia continues to undergo rapid intensification.  Maximum
flight-level winds were 123 kt, with believable SFMR values of 115
kt.  Satellite images show a small eye surrounded by very cold
clouds tops, especially in the western quadrant.  The initial wind
speed is set to 115 kt, making Idalia an extremely dangerous
category 4 hurricane.

The hurricane still has a few hours left to intensify before it
makes landfall. The biggest change to the intensity forecast is to
increase the wind speeds over southeastern Georgia and South
Carolina as the rapid motion and track close to the coast is
expected to keep the system near hurricane strength for longer.
Thus a Hurricane Warning has been issued for a portion of those
coasts, and the Hurricane Watch is extended northeastward.  After
the hurricane moves offshore, the wind field on the northwestern
side near eastern North Carolina is expected to be enhanced by a
cold front, and the Tropical Storm Watch has been upgraded to a
Tropical Storm Warning in that area.  The long-range intensity
forecast is quite uncertain with Idalia taking on some hybrid
characteristics due to a baroclinc trough. No changes were made at
this time, and the forecast remains close to the consensus.

Idalia is moving faster toward the north-northeast or 025/16 kt.
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, and the latest
guidance is significantly faster.  The new forecast is adjusted
toward the consensus, but could be too slow at long range.


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. Destructive life-threatening winds will occur 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
likely in portions of eastern Georgia and southeastern South
Carolina where Hurricane Warnings are now in effect.

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


INIT  30/0900Z 29.1N  84.1W  115 KT 130 MPH
 12H  30/1800Z 31.0N  82.7W   85 KT 100 MPH...INLAND
 24H  31/0600Z 33.1N  79.6W   60 KT  70 MPH...INLAND
 36H  31/1800Z 33.8N  76.1W   50 KT  60 MPH...OVER WATER
 48H  01/0600Z 33.3N  72.7W   50 KT  60 MPH
 60H  01/1800Z 32.4N  70.7W   45 KT  50 MPH
 72H  02/0600Z 31.5N  69.5W   45 KT  50 MPH
 96H  03/0600Z 30.7N  68.0W   45 KT  50 MPH
120H  04/0600Z 30.5N  66.0W   45 KT  50 MPH

Forecaster Blake

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