Tropical Depression Four Discussion Number   3
NWS National Hurricane Center Miami FL       AL042024
1100 PM EDT Fri Aug 02 2024

Shortwave infrared satellite imagery, Cuban radar data, and surface 
observations from Cuba and the Cayman Islands suggest that the 
disturbance has developed a closed circulation, and the center is 
located just off the south coast of Cuba.  Deep convection is still 
a bit fragmented, but there has been a persistent burst near the 
estimated center since earlier this afternoon.  The wind and 
pressure field could still be a little elongated within the 
southern semicircle, but overall the system appears to have enough 
organization to now be designated as a tropical depression.  The 
initial intensity remains 25 kt based on earlier observations.

The depression has not begun to turn yet, and the initial motion is 
west-northwestward, or 285/15 kt.  A turn toward the northwest and 
then north is expected over the weekend due to a break in the 
subtropical ridge caused by a trough over the eastern United 
States.  Since the system has not started to turn yet, this has 
caused all of the track guidance to shift west, and the updated NHC 
forecast is a bit west of the previous forecast along the eastern 
edge of the main cluster of models.  It is important to note that 
because of the forecast track being parallel to the west coast of 
Florida, the location and timing of a potential landfall cannot be 
pinned down at this time.  One additional significant change to the 
forecast is that the models seem to be showing the aforementioned 
trough leaving the cyclone behind early next week, which causes a 
much slower motion while the system is near the coasts of Georgia 
and South Carolina.  As a result, the new NHC forecast is notably 
slower than the previous forecast, particularly on days 4 and 5.

The westward shift to the track forecast now also keeps the system 
over the warm waters of the Gulf of Mexico longer, giving the 
system additional time to potentially strengthen.  In fact, the 
SHIPS guidance and all of the regional hurricane models show the 
cyclone reaching hurricane strength before reaching land in the Big 
Bend region of Florida in 2 to 3 days.  As a result, the new NHC 
forecast brings the intensity to 60 kt at 60 hours as the system is 
reaching land, but if model trends continue, it's possible that 
future forecasts could explicit show the system becoming a 
hurricane before it reaches land.  The intensity forecast is more 
uncertain on days 3 through 5 due depending on if the center moves 
back offshore or stays inland over the southeastern United States.


Key Messages:

1. Heavy rainfall may result in locally considerable flash and urban 
flooding across portions of Florida and the coastal areas of the 
Southeast U.S. this weekend through Wednesday. Isolated river 
flooding will also be possible.

2. Tropical storm conditions are expected Saturday night within the
Tropical Storm Warning area in southwest Florida from East Cape
Sable to Boca Grande and on the Dry Tortugas. Tropical storm 
conditions are possible in the remainder of the Florida Keys on 
Saturday and along the Florida west coast north of Boca Grande to 
Suwannee River Saturday night and Sunday where a Tropical Storm 
Watch is in effect.

3. There is a possibility of life-threatening inundation from storm
surge along portions of the west coast of Florida from Bonita Beach
to Suwannee River, including Tampa Bay and Charlotte Harbor, where a
Storm Surge Watch is in effect.

4. Impacts from storm surge, strong winds, and heavy rains are
possible elsewhere in Florida and along the southeast coast of the
United States from Georgia to North Carolina through the middle of
next week, and interests in those areas should continue to monitor
the progress of this system.  Additional watches and warnings will
likely be required on Saturday.


FORECAST POSITIONS AND MAX WINDS

INIT  03/0300Z 21.4N  79.7W   25 KT  30 MPH
12H  03/1200Z 22.6N  81.4W   30 KT  35 MPH...OVER CUBA
24H  04/0000Z 24.6N  83.3W   35 KT  40 MPH...OVER WATER
36H  04/1200Z 26.6N  84.1W   45 KT  50 MPH
48H  05/0000Z 28.4N  84.0W   55 KT  65 MPH
60H  05/1200Z 29.9N  83.4W   60 KT  70 MPH...INLAND
72H  06/0000Z 30.8N  82.5W   40 KT  45 MPH...INLAND
96H  07/0000Z 31.8N  80.9W   45 KT  50 MPH...OVER WATER
120H  08/0000Z 32.8N  79.4W   55 KT  65 MPH

$$
Forecaster Berg