Potential Tropical Cyclone Nine Discussion Number   3
NWS National Hurricane Center Miami FL       AL092024
1100 PM EDT Mon Sep 23 2024

Satellite imagery indicates that there has been little change in 
the organization of the system since earlier today.  Most of the 
deep convection is over the eastern part of the broad circulation.  
Animation of proxy-vis GOES images, and radar observations from 
Grand Cayman Weather Service suggest that the disturbance still 
does not have a well-defined center of circulation, so the system is 
kept as a potential tropical cyclone for the time being.  The 
advisory intensity is held at 30 kt which is in agreement with a 
Dvorak estimate from TAFB.  An Air Force reconnaissance aircraft is 
scheduled to investigate the area in a few hours to provide a 
better description of the system's structure along with an updated 
intensity estimate. 

The initial motion estimate is a rather uncertain 330/5 kt.  During 
the next day or so, the disturbance is expected to turn 
northwestward along the southern and southwestern side of a 
mid-level high pressure area.  Then, the high is expected to shift 
eastward while a mid-level trough drops into the 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. There is good agreement in the track guidance, and 
the official forecast is close to the corrected dynamical consensus 
model, HCCA, prediction.  This is also very similar to the previous 
NHC forecast.

An upper-level low over the northeastern Yucatan Peninsula has been 
imparting some southwesterly vertical wind shear over the 
disturbance.  This has probably caused a temporary disruption in 
development.  Dynamical guidance shows this low weakening with time, 
resulting in a reduction of shear in an environment that is 
otherwise very conducive for intensification.  The system is 
projected to move over waters of very high ocean heat content, 
which should lead to considerable strengthening during the forecast 
period.  The official intensity forecast is similar to the previous 
one and lies between the statistical-dynamical model guidance and 
the purely dynamical model predictions.  It should be noted that 
the 72-hour forecast allows for a little weakening after moving 
inland, so the cyclone is still expected to be at major hurricane 
strength at landfall. 

It should also be noted that the cyclone is expected to grow in 
size while it traverses the Gulf.  Thus, the storm surge, wind, and 
rainfall impacts will extend well away from the center, particularly 
to the east of the system. 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.


KEY MESSAGES:

1. The disturbance is forecast to intensify and be near hurricane
strength when it reaches the far northwestern Caribbean Sea Tuesday
night. 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. While
it is too soon to pinpoint the exact location and magnitude of
impacts, the potential for life-threatening storm surge and
damaging hurricane-force winds along the coast of the Florida
Panhandle and the Florida west coast is increasing.  Hurricane 
Watches and additional Storm Surge watches will likely be issued 
for a portion of that area Tuesday morning, and residents should 
ensure they have their hurricane plan in place.

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  24/0300Z 18.4N  82.4W   30 KT  35 MPH...POTENTIAL TROP CYCLONE
12H  24/1200Z 19.1N  83.5W   35 KT  40 MPH...TROPICAL CYCLONE
24H  25/0000Z 20.2N  84.6W   45 KT  50 MPH
36H  25/1200Z 21.6N  85.6W   60 KT  70 MPH
48H  26/0000Z 23.4N  85.8W   75 KT  85 MPH
60H  26/1200Z 26.2N  84.9W   90 KT 105 MPH
72H  27/0000Z 30.4N  83.9W   95 KT 110 MPH...INLAND
96H  28/0000Z 37.0N  85.0W   15 KT  15 MPH...POST-TROPICAL
120H  29/0000Z...DISSIPATED

$$
Forecaster Pasch