- Moderator
- #21
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Severe WX April 4th-6th, 2022 Severe Weather Threat
- Thread starter KevinH
- Start date
Clancy
Member
06Z GFS shows some wicked CAPE values on the 4/06 system, at least for Dixie Alley on Wednesday. Are these overdone?
Casuarina Head
Member
The 06Z GEFS members are also showing a notably more potent and negatively tilted trough vs. earlier runs.
Probably, however it doesn't really matter much concerning significant tornado threat as low level shear is very meagre where instability is strongest. If this scenario was to come of, definitely a wind and hail threat would materialise but without those classic Dixie Soundings probably nothing like a significant tornado outbreak.
MattPetrulli
Member
At least on 12z GFS for Wednesday, thinking the best tornado potential would be TN/KY/OH/WV, as that's where the best overlap of instability and shear is present.
CheeselandSkies
Member
Some of the most impressive soundings (tornado potential-wise) on that run actually occur at the forecast hour valid for 15Z (10 AM CDT) Wednesday across northern middle Tennessee. Fortunate that the first in this parade of systems to have really substantial CAPE values doesn't have the classic, insane shear profiles of the previous two; at least on the modeling at this point. It looks like the main surface low occludes and pushes northeast too quickly, veering the low-level winds parallel to the SW-NE oriented cold front.
However this is a complex scenario with a lot of moving parts, and it's hard to get a good feel for what the environment will be like across the uncontaminated warm sector. NAM and CAMs will probably only add to the confusion, at least at first when they get in range.
- Moderator
- #27
Model data has shown a better severe weather threat Tuesday across portions of eastern half of AL into Georgia than our previous events so far this year.
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- Moderator
- #28
A very concerning synoptic setup for southern half of Alabama and Georgia on Tuesday. The current GFS almost looks March 3rd, 2019 ish.
MattPetrulli
Member
Agreed, think there's some question about how far north the WF gets, GFS doesn't get it very far past Montgomery, AL still serves up a significant threat but a more limited warm sector. Euro gets it much further north to near the TN border maybe a little more southand has a pretty big warm sector but widespread convection which could limit convective organization and/or instability. NAM only goes out to 12z Tuesday on its 00z run but already has far more instability in MS/LA entering the warm sector, actually 12z NAM in itself would be a significant tornado threat in the early morning for MS/LA. Definitely needs to be watched.
Tuesday has now caught my eye, and things definitely look a lot more favourable for discrete supercells than past events this season, even at this range.
Per the Nam, the Warm Sector looks much more broad and unstable as well - 70F Dps quite widely even.
One concern for past 2 events was instability... here thermodynamics look pretty impressive/concerning. Tall and thick CAPE profiles modelled across S AL & MS during late Tues morning into afternoon.
Mid-level winds much less meridional, and with the larger and more unstable warm sector a partially discrete mode at least seems possible. And, while shear profiles aren't quite as extreme as last events, a 50kt LLJ will create pretty favourable hodographs anyways, though slightly offset from best intstability. Regardless, some discrete supercells, if they were to occur, could put down some strong-intense tornadoes.
To be honest, I do now feel it won't be long before one of these setups ends up with significant CAPE overlapped with significant shear with a favourable discrete mode... and resulting big problems.
Per the Nam, the Warm Sector looks much more broad and unstable as well - 70F Dps quite widely even.
One concern for past 2 events was instability... here thermodynamics look pretty impressive/concerning. Tall and thick CAPE profiles modelled across S AL & MS during late Tues morning into afternoon.
Mid-level winds much less meridional, and with the larger and more unstable warm sector a partially discrete mode at least seems possible. And, while shear profiles aren't quite as extreme as last events, a 50kt LLJ will create pretty favourable hodographs anyways, though slightly offset from best intstability. Regardless, some discrete supercells, if they were to occur, could put down some strong-intense tornadoes.
To be honest, I do now feel it won't be long before one of these setups ends up with significant CAPE overlapped with significant shear with a favourable discrete mode... and resulting big problems.
I might be wrong but it's really looking like Alabama might be in the crosshairs for the prime time of this event. I hope we have another semi fizzle event I guess we'll have to roll the dice again and see what happens.
MattPetrulli
Member
Yeah, even 12z NAM is a high-end event for MS/AL/FL/GA. GFS is too progressive it seems and kinda limits the severe threat still, that may be the GFS's progressive bias however. Euro is a little closer to the NAM but does have widespread convection which could still limit the threat. However, quite a look for this far out, would expect a day 3 enhanced if this keeps up.
CheeselandSkies
Member
At first glance the low-level winds just seemed too veered (all west of due south); but because the 500s are more westerly with this trough orientation there still might be enough directional shear, also remembering what @Fred Gossage said about this not being Oklahoma. I've noticed the NAM forecast hodographs have more curvature than the GFS ones did on prior ones.
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MattPetrulli
Member
18z GFS was pretty tame on potential for Tuesday-Wednesday and further on, Euro trended down a little on instability and NAM was a little more progressive which trended down instability a little bit but still has a significant event Tuesday. Euro isn't far from a significant event still. Just something of note.
Monday-Monday Night 
12z NAM still suggesting a favourable paramater space for tornadoes during Tuesday, especially across Southern Alabama and Georgia.
The run models an MCS, with some hints of something more discrete. Needs watching. Wouldn't be surprised to see an eventual 10# by Day 1.
The run models an MCS, with some hints of something more discrete. Needs watching. Wouldn't be surprised to see an eventual 10# by Day 1.
Clancy
Member
The D4 is now quite large. SPC mentions linear setup with wind and tornado threat.
When I look at the models even though this is the it's the furthest out in the forecast it looks the most troubling
Clancy
Member
Doesn't seem like much shear to support major tornado business thankfully, but would still be a substantial wind threat for the Atlanta Metro.
Clancy
Member
I can see Tuesday could be pretty hairy regarding tornado potential, though shear seems a lot weaker on Wednesday. Nevertheless, I usually don't like seeing CAPE modelled as high as it's supposed to be for Wednesday for GA. I'm not all that good at reading into the details beyond some of the soundings/model data, so are there some particular things that would point to Wednesday being more serious tornado-wise than currently forecast?
