Tropical Storm Debby Discussion Number   7
NWS National Hurricane Center Miami FL       AL042024
1100 PM EDT Sat Aug 03 2024

NOAA and Air Force Reserve Hurricane Hunter aircraft have been 
investigating Debby during the past few hours and have found that 
the winds have increased slightly and the central pressure has 
fallen.  The NOAA P-3 plane reported SFMR measurements of 35-40 kt 
east of the center over the Straits of Florida, and dropsonde data 
indicate that the central pressure has fallen to 1003 mb.  The 
initial intensity is therefore raised to 40 kt.

Debby is gradually turning toward the right and slowing down, and 
the initial motion is northwestward, or 320/12 kt.  A large mid- to 
upper-level trough over the eastern United States has created a 
break in the subtropical ridge, which will cause Debby to move 
northward over the eastern Gulf of Mexico and approach the 
Florida Big Bend region over the next day or two.  The track 
guidance is in good agreement during this period, and the NHC track 
has only been shifted slightly east to account for a slight 
relocation of the initial position based on the aircraft data.  
After 2-3 days, the steering currents around Debby collapse, and 
the cyclone is expected to creep northeastward at less than 5 kt 
across northern Florida to near the coasts of Georgia and South 
Carolina by day 5.  While there is model disagreement on exactly 
where Debby will end up on day 5, there is high confidence that the 
storm will not be moving very fast, and this slow motion will have 
major implications for the associated hazards, particularly heavy 
rainfall and flooding.

Low vertical shear and very warm waters (as warm as 32 degrees 
Celsius within Apalachee Bay) are likely to support additional 
strengthening while Debby approaches the Florida Big Bend.  The 
intensity guidance has increased a bit on this cycle.  Most of the 
regional hurricane models are showing Debby reaching hurricane 
strength before it reaches the coast, while the 
statistical-dynamical SHIPS and LGEM models have increased to the 
75-80-kt range.  In addition, the Rapid Intensification indices are 
showing a 1-in-3 chance of a 45-kt increase in intensity over the 
next 36 hours.  Based on these model data, the NHC intensity 
forecast has been increased to 75 kt in 36 hours, just before the 
center of Debby is expected to reach the coast.  Weakening is 
anticipated after landfall, but Debby's intensity on days 3 through 
5 is highly uncertain and is dependent on whether the center moves 
over the Atlantic waters and for how long.


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 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 on Sunday.


FORECAST POSITIONS AND MAX WINDS

INIT  04/0300Z 24.4N  83.6W   40 KT  45 MPH
12H  04/1200Z 25.9N  84.2W   50 KT  60 MPH
24H  05/0000Z 27.8N  84.3W   60 KT  70 MPH
36H  05/1200Z 29.3N  84.0W   75 KT  85 MPH
48H  06/0000Z 30.3N  83.3W   55 KT  65 MPH...INLAND
60H  06/1200Z 31.0N  82.4W   40 KT  45 MPH...INLAND
72H  07/0000Z 31.2N  81.5W   40 KT  45 MPH...INLAND
96H  08/0000Z 31.6N  80.2W   45 KT  50 MPH...OVER WATER
120H  09/0000Z 33.0N  80.5W   40 KT  45 MPH...INLAND

$$
Forecaster Berg