ATL: DEBBY - Post-Tropical - Discussion

[StPeteMike]

Pressure falling at Sand Key Lighthouse(offshore of Key West), now at 1008 mb about 100 miles away from the center. The graph really puts it in perspective.

https://www.ndbc.noaa.gov/show_plot.php ... _label=EDT

1008 mb 100 away from center, wow! Obviously, Debby is a broad girl, but that has to justify at least a few mb less than the 5 PM advisory has her.

Can’t wait for recon!

[xironman]

Fast lane to developing a core? It is just off of Cuba, 48 hrs to go.

[AtlanticWind]

I disagree with the current movement by NHC.... based on radar and satellite. I believe it has slowed and is wobbling around. Possibly a little more west than north.

I don’t really see that myself ,regardless though Debby is being captured by the trough
and will be moving northwest turning north tomorrow morning

[FLLurker32]

Everyone here has primarily been focused on where the CoC starts, and rightfully so BUT the timing of that NE turn is just as critical to where Debby lands and time spent over the warm gulf waters.

NHC cone at 5pm seems to be still centering on the uncertain timing for the turn. Next 12 hours will be interesting.

[toad strangler]

I don't ever remember the NHC forecast discussion mentioning the CMC model like they have with this system during the past couple of Discussions, if ever.

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.

CMC has consistently been showing this since at least 12z yesterday 8/2

[stormhunter7]

The hot tower that blew up recently with a lot of lightning in it is rotating in the mid levels, and appears is trying to pull the surface center that's north of it back towards it, IMO.

[cycloneye]

 https://x.com/NWSMiami/status/1819846943167987868

[5t0rmsguy]

Kinda off topic, but in satellite imagery the yellow dots mean lightning right?

[USTropics]

Here is the last 3 hours of mesoscale frames (~200). Definitely get a good pulse up currently. Would imagine this will start to level off soon with DMIN before another ramp up late tonight:

[WaveBreaking]

[NDG]

Here is the last 3 hours of mesoscale frames (~200). Definitely get a good pulse up currently. Would imagine this will start to level off soon with DMIN before another ramp up late tonight:
https://i.imgur.com/lRCyFZx.gif

Legit Tropical Storm on the satellite image!

[tolakram]

Yea, I was going to say this thing looks scary organized already.

[LarryWx]

I looked over past tracks of TCs back to 1851. Of those that moved from the GOM inland over W FL N of Tampa through the panhandle, I couldn’t find even one that then moved offshore SE US followed by a curl back NW back into the SE coast like the last few Euro/GFS runs. The closest I could find is Easy of 1950, which could have done it had it first gone offshore FL before curling back:

https://upload.wikimedia.org/wikipedia/ ... _track.png

So, whereas climo doesn’t tell me a curl back NW into the SE coast a la GFS/Euro can’t happen, it does tell me to not be surprised if that ends up not happening and to almost expect it to not.

[tolakram]

saved loop


source: https://weather.cod.edu/satrad/?parms=meso-meso2-02-96-1-100-6&checked=map&colorbar=undefined

[cycloneye]

The D storm on average forms on the 15th of August.

 https://x.com/philklotzbach/status/1819842035714756722

[tolakram]

Hurricane warnings issued, and there seems to be a pretty good chance this goes in strengthening unless I'm missing something.

000
WTNT44 KNHC 032054
TCDAT4

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

[tolakram]

[NDG]

I don't ever remember the NHC forecast discussion mentioning the CMC model like they have with this system during the past couple of Discussions, if ever.

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.

CMC has consistently been showing this since at least 12z yesterday 8/2

Looking back I actually see the ICON to be more consistent than the CMC. It is fairly close to both the Euro and GFS. I doubt the CMC's solution since yesterday come to fruition of its solution of Debby staying inland over the SE US..

[Hypercane_Kyle]

This is a wildly better organized storm vs six hours ago.

[Hurricane2022]

This is a wildly better organized storm vs six hours ago.

https://i.imgur.com/fejLrAS.jpeg

I'm starting to think that we could see an "surprise" major hurricane like Idalia and Michael...