ATL: DEBBY - Post-Tropical - Discussion

[wxman57]

Do you suppose the current forecast from the NHC might be greatly overestimating wind speeds during Debby's stall/approach to second landfall, or would restrengthening/maintaining strength through that period be possible even for a system that's lost its core?

It's hard to say whether Debby will be able to regenerate its core prior to moving back inland into SC Thursday morning. Models seem to think so, but it will be west of the Gulf Stream over cooler shelf waters. It has a long way to go to rebuild its core. The NHC's job is to keep people safe. Sometimes that means over-warning just in case the storm does something unexpected. They'd rather do that than say "don't worry about it" and have Debby strengthen unexpectedly and kill people. Debby could produce some 50-60 mph wind prior to landfall, mostly out over the water east of the center.

[tolakram]

saved loop

[cycloneye]

 https://x.com/AndyHazelton/status/1820803007795036595

[Steve]

Is it just me, or does this look like its getting awfully close to the coast? It's not supposed to be this far east until Tues. 2pm

Yeah kind of. Mesoscales are running on TT - I didn’t look for them elsewhere. Some hint of getting to the coast and riding it slow before coming off for a day or so and going back in. But it looks like a bunch of coastal areas have a shot at the north, west and south side of the center of circulation. And some people gonna get hit for hours and hours while it’s on the coast.

JB has been saying this would move to the coast quicker and go further out. So far it looks like he is getting this right

I don't usually pay a lot of attention to him though I will skim the Saturday summaries during tropical season to see if he has anything to add or make me think about. Seemed like this past weekend he was going with a combination of ICON and EC and specifically professed his affinity for the ICON these days. You figure the center would be able to find the water again but whether that's just along the coast or if it actually goes out drops and then comes up remains to be seen. Pressures should be pretty low, but as wx57 and others have noted, it's not likely to be that big of a wind event unless you're under part of the ring of the CoC for a long period of time. Should be plenty of rain though which I feel like that and coastal flooding will be the main impacts for GA/SC/NC though if it gets back to the 980's, even though the wind won't respond as if it was a developing system, it could still bring a punch or two.

[xironman]

 https://x.com/AndyHazelton/status/1820803007795036595

So the whole cooler shelf water thing. I realize the gulf stream is much deeper, and contains a lot of heat for larger storms. But looking at the observations most buoys are in the 82-84 degree area, which does not strike me a that cool. I think a bigger inhibitor is all the drier continental air being dragged into it.

[wxman57]

So the whole cooler shelf water thing. I realize the gulf stream is much deeper, and contains a lot of heat for larger storms. But looking at the observations most buoys are in the 82-84 degree area, which does not strike me a that cool. I think a bigger inhibitor is all the drier continental air being dragged into it.

Water along the coast is definitely cooler than in the Gulf Stream to the east. However, the more significant thing is that the core has dissipated and drier air is being ingested from the west and southwest. It's hard for a storm to recover from loss of its core.

[JRD]

I wouldn't mind some rain if it means the drought is going away.

[syfr]

It's hard for a storm to recover from loss of its core.

This is what those of us in east central NC call "good news"

[SootyTern]

Keeping an eye on this in the Northeast.
From today's NWS NY Area discussion (1110AM)

.LONG TERM /THURSDAY THROUGH MONDAY/...
Key Points:

* Potential remains for a moderate to high impact flooding event
late Thursday into Saturday as multiple frontal systems
interact with tropical moisture associated with Debby.

* The future track of Debby, and larger scale weather systems
influencing the storm`s track, will play a big part in how this
portion of the forecast unfolds. Refer to the latest official
forecasts from the National Hurricane Center.

Not much change with the 00Z globals as the GFS continues to
linger the circulation of Debby too long over the Southeast and
then shear it out when finally moving northeast late Friday into
the the first half of this weekend. However, the ECMWF/Canadian
while quicker are becoming similar in that the low becomes
absorbed into the mid latitude cold front approaching from the
west. This results in less of defined circulation as the low
works across the area Saturday.

Even before the actual circulation of Debby (no matter what its
classification) approaches, we may have to deal with a tropical
predecessor heavy rainfall event on Friday as a leading warm front
approaches from the south, with good southerly moisture transport
and possibly enhanced lift via weakly coupled jet streaks, one
departing over New England and and another riding up the coast.
In addition, a cold front associated with an amplifying upper
trough across the Great Lakes and Ohio Valley states sends a
strong cold front across the area on Saturday, interacting with
the tropical moisture and producing another potential round of
heavy rain. Deterministic/ensemble QPF`s continue to bear this
out, showing fairly high probabilities of 4+ inches of total
rainfall through the weekend centered over the CWA or in areas
just north.

All the above are still highly uncertain and subject to changes
in the future track and status of Debby as the circulation
eventually comes northward.

[Steve]

Close to the coast near Ga-SC border. Should come off and move east or ESE for a while in the next half day or so.

https://www.tropicaltidbits.com/sat/sat ... t=vis_swir

[Powellrm]

https://youtu.be/uiZQqHl4yuw?si=SUQ3rkyOoPg18KhJ

[LarryWx]

 I estimate that I’m at 8.5” so far from Debby (over last ~30 hours) with only ~1/2” since 2AM allowing good progress on drainage. If we were to not get too much more from this point forward (where I’m leaning now), I’d be near the low end of the range of predictions, which had a pretty good amount for today and tomorrow. As of last night I had guessed at least another 4” between then and Thursday. Still an 8.5” rain is enough to qualify as a very big rain event due to its rarity and likely is the largest since Matthew of early Oct of 2016. Also, some nearby areas (Effingham and Jasper counties) got 10-11” per CoCoRaHS.

 The storm is currently centered just E of here along the coast about to be offshore. Winds and rain are very light near the storm center.

[Nimbus]

Close to the coast near Ga-SC border. Should come off and move east or ESE for a while in the next half day or so.

https://www.tropicaltidbits.com/sat/sat ... t=vis_swir

Its coming off the coast just south of Parris island, SC.
East wind 1001 MB with shallow broad pressure gradient.
Probably going to moisten up again overnight with squall lines and persistent rain where the squall lines train.

Water vapor loop shows moisture wrapping in already.

[Kohlecane]

 I estimate that I’m at 8.5” so far from Debby (over last ~30 hours) with only ~1/2” since 2AM allowing good progress on drainage. If we were to not get too much more from this point forward (where I’m leaning now), I’d be near the low end of the range of predictions, which had a pretty good amount for today and tomorrow. As of last night I had guessed at least another 4” between then and Thursday. Still an 8.5” rain is enough to qualify as a very big rain event due to its rarity and likely is the largest since Matthew of early Oct of 2016. Also, some nearby areas (Effingham and Jasper counties) got 10-11” per CoCoRaHS.

 The storm is currently centered just E of here along the coast about to be offshore. Winds and rain are very light near the storm center.

10.12" Lady's Island here started measuring Sunday at 7PM till this AM at 7AM, it wasn't as bad as I thought, some areas have some flooding however nothing too serious near me. Most major roadways accessible. Matthew was rough, and a notable mention to Joaquin and the moisture swath it created over SC from a digging trough

[LarryWx]

 I estimate that I’m at 8.5” so far from Debby (over last ~30 hours) with only ~1/2” since 2AM allowing good progress on drainage. If we were to not get too much more from this point forward (where I’m leaning now), I’d be near the low end of the range of predictions, which had a pretty good amount for today and tomorrow. As of last night I had guessed at least another 4” between then and Thursday. Still an 8.5” rain is enough to qualify as a very big rain event due to its rarity and likely is the largest since Matthew of early Oct of 2016. Also, some nearby areas (Effingham and Jasper counties) got 10-11” per CoCoRaHS.

 The storm is currently centered just E of here along the coast about to be offshore. Winds and rain are very light near the storm center.

10.12" Lady's Island here started measuring Sunday at 7PM till this AM at 7AM, it wasn't as bad as I thought, some areas have some flooding however nothing too serious near me. Most major roadways accessible. Matthew was rough, and a notable mention to Joaquin and the moisture swath it created over SC from a digging trough

Joaquin didn’t do much in this area. We got ~1”. The setup with Joaquin was unlike anything I have ever seen!

As the Debby center moved to the SE offshore finally putting us on the backside, winds picked up somewhat and steady mainly moderate rains resumed about 2 hours ago after little rain since late last night. I had been at ~8.5” for the storm before this. We’ll see how much gets added from this and more to come tonight.

[WaveBreaking]

Dry air from a nearby shortwave found its way into Debby's center during its time over land. Weak convection is starting fire over the center since it's trying to mix the dry air out.

[BobHarlem]

Boy has convection waned as dry air found its way into the middle, although the southern side looks like it may close off with moisture (leaving the dry center) so maybe some more convection will rebuild over water.

I don't any way this thing gets reorganized much though.

[ScottNAtlanta]

It really doesn't even look tropical anymore. I don't think this will strengthen much even if it makes it to the Gulfstream, it wont have enough time there

[Kazmit]

Looks ridiculous on radar. The whole storm is just a thin hula hoop of thunderstorms.

[birddogsc]

Euro, GFS, HRRR, and the hurricane models all have Debby doing some kind a of loop. Super.