Tropical Storm Debby Discussion Number   6
NWS National Hurricane Center Miami FL       AL042024
500 PM EDT Sat Aug 03 2024

The tropical cyclone has become better organized since the last 
advisory, with the circulation center becoming better defined over 
the southeastern Gulf of Mexico and areas of outer convective 
banding to the north and south of the central region.  A 
combination of earlier scatterometer data, surface observations in 
the Florida Keys, and ship reports in the Straits of Florida shows 
an area of 30-35 kt winds located about 120 n mi from the center in 
the eastern semicircle.  Based on this information, Tropical 
Depression Four is upgraded to Tropical Storm Debby.

The initial motion is now northwest or 310/13 kt. A large mid- to 
upper-level trough over the central United States is creating a 
break in the subtropical ridge, and Debby is expected to turn 
northward into this break in about 24 h.  This should be followed 
by a gradual turn toward the northeast at a slower forward speed 
through 60 h.  This motion should bring the center near or over the 
northern Gulf coast in roughly 48 h.  After landfall, weakening 
steering currents should cause the cyclone to slow down while it 
moves northeastward or eastward over parts of northern Florida and 
Georgia.  The uncertainty in the forecast increases significantly 
after 60 h as the cyclone interacts with a portion of the U.S. 
trough.  The latest GFS and ECMWF models show a slow eastward 
motion into the Atlantic, followed by a turn toward the north or 
northwest that brings the center back inland. On the other hand, 
the Canadian model is still forecasting Debby to move slowly 
northeastward across the southeastern states and does not bring it 
over the Atlantic.  This portion of the new forecast track 
continues to show a slow motion and leans toward the GFS/ECMWF 
solutions.

Conditions are favorable for strengthening over the Gulf of Mexico 
with warm sea surface temperatures and light shear.  
Intensification is likely to be slow during the first 12-24 h, then 
proceed at a faster rate after the cyclone develops an organized 
inner core.  The new intensity forecast calls for a peak intensity 
of 65 kt at landfall on the Gulf coast of Florida in best agreement 
with the HWRF model. Weakening is forecast after landfall while the 
system moves over the southeastern United States. Beyond 72 h, the 
intensity forecast remains quite uncertain due to the possibility 
of land interaction and how much interaction will occur with the 
aforementioned mid-latitude trough.


Key Messages:

1. Heavy rainfall will likely result in considerable flash and urban 
flooding across portions of Florida and the coastal areas of the 
Southeast this weekend through Thursday. Significant river flooding 
is also expected.

2.  Hurricane conditions are expected on Monday along portions of 
the Florida Big Bend region where a Hurricane Warning is in effect, 
with tropical storm conditions beginning late Sunday. Tropical storm 
conditions are expected through Monday farther south within the 
Tropical Storm Warning along Florida's west coast, including the 
Tampa Bay area and the Lower Florida Keys.

3. There is a danger of life-threatening storm surge inundation 
along portions of the Gulf coast of Florida from Aripeka to Indian 
Pass. Life-threatening storm surge is possible south of Aripeka to 
Bonita Beach, including Tampa Bay and Charlotte Harbor.

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 tonight or on Sunday.


FORECAST POSITIONS AND MAX WINDS

INIT  03/2100Z 23.9N  83.2W   35 KT  40 MPH
12H  04/0600Z 25.3N  84.1W   40 KT  45 MPH
24H  04/1800Z 27.2N  84.6W   45 KT  50 MPH
36H  05/0600Z 28.9N  84.4W   55 KT  65 MPH
48H  05/1800Z 30.2N  83.8W   65 KT  75 MPH...INLAND
60H  06/0600Z 31.0N  83.0W   40 KT  45 MPH...INLAND
72H  06/1800Z 31.3N  82.0W   35 KT  40 MPH...INLAND
96H  07/1800Z 31.5N  80.5W   40 KT  45 MPH...OVER WATER
120H  08/1800Z 33.0N  80.4W   50 KT  60 MPH...INLAND

$$
Forecaster Beven