Potential Tropical Cyclone Nine Discussion Number   4
NWS National Hurricane Center Miami FL       AL092024
500 AM EDT Tue Sep 24 2024

Satellite images indicate that the system remains poorly organized. 
A large area of deep convection is on the eastern side of the broad 
circulation with no defined central features, and dropsondes 
from the Air Force and NOAA aircraft indicate that low-level 
circulation remains poorly defined.  The initial wind speed is kept 
at 30 kt, in agreement with many dropsondes around that value.  

The best estimate of initial motion is northwestward at about 7 kt. 
This general motion is expected today while the disturbance moves 
around a high-pressure area over the southeastern United States.  
The cyclone is expected to gradually turn northward on Wednesday as 
the high shifts eastward ahead of a mid-level trough dropping into 
the south-central United States.  This evolution of the steering 
pattern should cause the system to accelerate northward to 
north-northeastward over the eastern Gulf of Mexico and toward the 
northeastern Gulf Coast through Thursday.  The biggest change to the 
model guidance overnight is that the guidance mean is a bit slower, 
with the GFS model faster than most of the aids.  However, this 
remains a very consistent set of models, and very little overall 
change was made to the official forecast.  Hopefully an ongoing NOAA 
G-IV aircraft mission will help provide useful data for any future 
track refinements.

Southwesterly shear continues over the disturbance, though the 
models are insistent that this shear will abate as an upper-level 
low over the northeastern Yucatan Peninsula weakens today and 
tomorrow.  Otherwise, conditions look quite favorable for 
strengthening over the eastern Gulf of Mexico on Wednesday and 
Thursday, with the system likely moving over extremely deep and 
warm waters, along with a favorable trough interaction, and many of 
the forecast aids are showing rapid intensification over the 
eastern Gulf of Mexico.  The intensity guidance is very close to 
the previous NHC intensity forecast and continues to indicate that 
this system will become quite large and powerful before landfall.

Due to the forecast large size of this system, storm surge, wind, 
and rainfall impacts will extend well away from the center, 
particularly on the east side.  In addition, the fast 
forward speed while it crosses the coast will likely result in 
farther inland penetration of strong winds over parts of the 
southeastern United States after landfall.  Hurricane and Storm 
Surge Watches have been issued this morning, and further watches 
and warnings are likely later today.


KEY MESSAGES:

1. The disturbance is forecast to intensify and be near hurricane
strength when it reaches the far northwestern Caribbean Sea early 
Wednesday.  Tropical storm conditions are expected over portions of
western Cuba and the northeastern coast of the Yucatan Peninsula
with hurricane conditions possible.

2. The system is expected to intensify into a major hurricane before 
it approaches the northeastern Gulf Coast on Thursday, and the 
potential for life-threatening storm surge and damaging 
hurricane-force winds along the coast of the Florida Panhandle and 
the Florida west gulf coast is increasing.  Hurricane and Storm 
Surge Watches have been issued, and residents should ensure they 
have their hurricane plan in place, and also follow advice given by 
local officials. 

3. Potential Tropical Cyclone Nine will bring heavy rain to portions
of the western Caribbean, which will cause considerable flooding
and mudslides across western Cuba.  Heavy rainfall will likely
result in locally considerable flash and urban flooding across
portions of Florida, with isolated flash and urban flooding
possible across the Southeast, Southern Appalachians, and the
Tennessee Valley Wednesday through Friday. Minor to isolated
moderate river flooding will be possible.


FORECAST POSITIONS AND MAX WINDS

INIT  24/0900Z 18.9N  83.0W   30 KT  35 MPH...POTENTIAL TROP CYCLONE
12H  24/1800Z 19.6N  84.2W   40 KT  45 MPH...TROPICAL CYCLONE
24H  25/0600Z 20.7N  85.7W   50 KT  60 MPH
36H  25/1800Z 22.0N  86.2W   65 KT  75 MPH
48H  26/0600Z 24.3N  85.6W   80 KT  90 MPH
60H  26/1800Z 27.8N  84.4W  100 KT 115 MPH
72H  27/0600Z 31.9N  83.5W   60 KT  70 MPH...INLAND
96H  28/0600Z 38.5N  85.5W   15 KT  15 MPH...POST-TROPICAL
120H  29/0600Z...DISSIPATED

$$
Forecaster Blake