Tropical Storm Idalia Forecast Discussion Number 7

By | August 28, 2023

WTNT45 KNHC 280859

Tropical Storm Idalia Discussion Number   7
NWS National Hurricane Center Miami FL       AL102023
400 AM CDT Mon Aug 28 2023

Idalia has intensified overnight.  Data from an Air Force Reserve 
Hurricane Hunter aircraft showed believable surface winds of 50-55 
kt and a central pressure falling to around 989 mb.  The wind data 
is also confirmed by NOAA buoy 42056, located just southeast of 
the center, which has reported maximum 1-minute adjusted sustained 
winds above 50 kt within the past hour or two. These data support 
raising the initial wind speed to 55 kt.

It seems like Idalia is finally on the move, with aircraft fixes 
indicating a northward motion of about 6 kt.  This motion should 
continue through Tuesday as Idalia moves between a mid-level trough 
over the central Gulf of Mexico and a strengthening ridge over the 
Greater Antilles.  The storm is likely to move faster to the 
north-northeast and northeast by early Wednesday due to a deeper 
trough that is expected to swing across the mid-western United 
States.  The new NHC track forecast is quite close to the last one 
with little significant changes to the track guidance.  It should be 
emphasized that only a small deviation in the track could cause a 
big change in Idalia's landfall location in Florida due to the 
paralleling track to the west coast of the state.

The center of Idalia is on the northern edge of the deep convective 
mass, a refection of moderate northwesterly shear, and the last 
aircraft pass showed a vortex tilted southward with height.  This 
shear and structure should persist for about the next 24 hours, 
helping to keep the intensity of the storm from increasing too 
quickly despite the extremely warm waters it will be traversing.  
The NHC short-term forecast will continue to indicate Idalia as a 
hurricane near western Cuba, similar to the guidance.  

Over the Gulf of Mexico, the environment is forecast to become 
conducive for significant strengthening of Idalia due to a new 
trough dropping south over the western Gulf of Mexico as a 
upper-level ridge builds near the cyclone.  Additionally, Idalia 
will be moving over waters near 31C, and some of the guidance is 
even indicating favorable jet dynamics on Wednesday with Idalia in 
the right-rear quadrant of the jet over the southeastern United 
States.  The bottom line is that rapid intensification is becoming 
increasingly likely before landfall, and the NHC forecast now 
explicitly indicates it between 24-48 h in the forecast.  This is 
consistent with almost all of the regional hurricane models and the 
SHIPS rapid intensification indices, which are 5-10 times the 
climatological mean.  The new prediction shows a 100-kt hurricane 
over the eastern Gulf of Mexico at 48 hours, but Idalia should keep 
strengthening up to landfall along the Gulf coast of Florida.  
Interests within the storm surge and hurricane watch areas are urged 
to prepare for possible significant impacts and monitor future 
updates to the forecast for this increasingly dangerous situation.


1. Idalia is now forecast to become a major hurricane before it 
reaches the Gulf coast of Florida.  The risk continues to increase 
for life-threatening storm surge and dangerous hurricane-force 
winds along portions of the west coast of Florida and the Florida 
Panhandle beginning as early as late Tuesday.  Storm surge and 
hurricane watches are in effect for portions of the west coast of 
Florida and the coast of the Florida Panhandle, and residents in 
these areas should monitor updates to the forecast and follow any 
advice given by local officials.

2. 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.

3. Hurricane-force winds are expected across portions of far
western Cuba later today.  Heavy rainfall is also expected across
portions of western Cuba and may produce areas of flash and urban 
flooding as well as landslides across western Cuba.


INIT  28/0900Z 20.1N  85.2W   55 KT  65 MPH
 12H  28/1800Z 21.1N  85.1W   65 KT  75 MPH
 24H  29/0600Z 22.6N  85.1W   70 KT  80 MPH
 36H  29/1800Z 24.8N  84.8W   85 KT 100 MPH
 48H  30/0600Z 27.7N  84.0W  100 KT 115 MPH
 60H  30/1800Z 30.7N  82.1W   65 KT  75 MPH...INLAND
 72H  31/0600Z 32.8N  79.0W   55 KT  65 MPH...OVER WATER
 96H  01/0600Z 34.5N  72.0W   50 KT  60 MPH
120H  02/0600Z 34.5N  67.0W   50 KT  60 MPH

Forecaster Blake

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