Hurricane Idalia Discussion Number  11
NWS National Hurricane Center Miami FL       AL102023
400 AM CDT Tue Aug 29 2023

Radar data from western Cuba indicates that Idalia is becoming 
better organized.  Most of an eyewall has formed, with much more 
curvature in the banding features and overall radar pattern.  
Satellite imagery also shows the center of Idalia firmly within the 
central dense overcast.  Thus, the initial wind speed is raised to 
65 kt, in accordance with the latest TAFB satellite classification.

The hurricane is accelerating northward this morning, now moving at 
about 9 kt.  Idalia should move faster to the north or 
north-northeast through landfall on Wednesday between mid-level 
ridging over Florida and a trough dropping into the western Gulf of 
Mexico.  There has been a westward shift in the model guidance 
overnight, perhaps due to the trough tugging Idalia more 
northward before taking a north-northeast turn.  It should be 
noted that the ECMWF ensemble shows many of its strongest members 
on the eastern side of its guidance envelope, which is a 
reasonable place to be given the synoptic pattern.  The new NHC 
forecast is adjusted a little to the west but is now east of the 
model consensus on the eastern side of the reliable model guidance. 
After Idalia leaves the eastern United States coastline, the track 
forecast becomes highly uncertain and little change was made to the 
previous forecast.  

With an inner core now present, the stage is set for Idalia to 
rapidly intensify before landfall. Shear should continue to lower 
over the cyclone as an upper-level trough departs the northeastern 
Gulf of Mexico and ridging builds closer to the cyclone.  These 
changes, combined with extremely warm and deep waters the hurricane 
will be traversing, all strongly point to rapid intensification.  
The new forecast is similar to the previous one, and confidence is 
increasing in an extremely dangerous major hurricane making landfall 
Wednesday along the west coast or Big Bend region of Florida.

KEY MESSAGES:

1. There is a danger of life-threatening storm surge inundation
along portions of the Florida Gulf Coast where a Storm Surge Warning
is in effect, including Tampa Bay and the Big Bend region of
Florida. Inundation of 8 to 12 feet above ground level is expected
somewhere between Chassahowitzka and Aucilla River.  Residents in
these areas should follow any advice given by local officials.

2. Hurricane conditions are expected within portions of the
Hurricane Warning area along the Florida Gulf Coast, with the
potential for destructive winds where the core of Idalia moves
onshore. Strong winds will also spread inland across portions of
northern Florida near the track of the center of Idalia.

3. Heavy rainfall is expected across portions of western Cuba and 
may produce areas of flash and urban flooding as well as landslides. 
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 beginning today 
into Wednesday, spreading into portions of the eastern Carolinas 
Wednesday into Thursday.


FORECAST POSITIONS AND MAX WINDS

INIT  29/0900Z 23.1N  85.0W   65 KT  75 MPH
12H  29/1800Z 24.9N  84.8W   85 KT 100 MPH
24H  30/0600Z 27.8N  84.3W  105 KT 120 MPH
36H  30/1800Z 30.6N  82.9W   70 KT  80 MPH...INLAND
48H  31/0600Z 32.7N  80.5W   50 KT  60 MPH...INLAND
60H  31/1800Z 33.8N  77.5W   50 KT  60 MPH...OVER WATER
72H  01/0600Z 33.9N  74.4W   50 KT  60 MPH
96H  02/0600Z 33.3N  71.5W   45 KT  50 MPH
120H  03/0600Z 32.5N  70.5W   40 KT  45 MPH

$$
Forecaster Blake