Severe WX 1/24/21-1/26/21 Severe Event (Fultondale, AL) (1 Viewer)

andyhb

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Annnnnnnnnd everything comes in flat/sheared out at 00z. Lol.
 

Fred Gossage

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Annnnnnnnnd everything comes in flat/sheared out at 00z. Lol.
We still get a northerly surface low track, even on the op GFS now, but everything is definitely flat. There's either straight or slightly anticyclonic flow over a large portion of the warm sector. Doesn't mean we can't have severe or tornadic storms, but it definitely puts a lid on the ceiling for this.
 

Fred Gossage

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I don't think there's a way for us to not deal with the straight jet synoptic look with this, but now even the operational GFS has caved toward having a deeper surface low on a track farther north, with a large EML overtop the warm sector, and quality instability (by winter standards) in place. I think the straight jet and lack of better cyclonic vorticity advection and better height falls over the warm sector limits this event in scope by number of storms... but I'm not sure it does much at all to limit intensity of the few storms that may form. The environment Monday will likely be supportive of significant tornadoes. It's a matter of getting a couple of storms to sustain themselves long enough in that environment. I don't think we will have many of them, but I can't imagine us not having at least two or three.
 
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Austin Dawg

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I don't think there's a way for us to not deal with the straight jet synoptic look with this, but now even the operational GFS has caved toward having a deeper surface low on a track farther north, with a large EML overtop the warm sector, and quality instability (by winter standards) in place. I think the straight jet and lack of better cyclonic vorticity advection and better height falls over the warm sector limits this event in scope by number of storms... but I'm not sure it does much at all to limit intensity of the few storms that may form. The environment Monday will likely be supportive of significant tornadoes. It's a matter of getting a couple of storms to sustain themselves long enough in that environment. I don't think we will have many of them, but I can't imagine us not having at least two or three.

Where is this likely to happen and when? Me, the wife, and the kids live just north of Austin but I have family in Smithville, Mississippi and Alabama. I try to keep an eye on everything after April 2011.
 

Fred Gossage

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Where is this likely to happen and when? Me, the wife, and the kids live just north of Austin but I have family in Smithville, Mississippi and Alabama. I try to keep an eye on everything after April 2011.
There may be a few strong storms on Sunday in north to northeast TX. SPC has an outlook for out there. The Monday risk looks like a general MS/AL/TN ordeal, maybe leaking over into portions of surrounding states.
 
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Where is this likely to happen and when? Me, the wife, and the kids live just north of Austin but I have family in Smithville, Mississippi and Alabama. I try to keep an eye on everything after April 2011.
Looks like the arklatex region over to east there Mississippi Alabama . Gfs has slp further north. Wouldn’t be suprise southern section Tennessee even.
 

Fred Gossage

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Looks like the arklatex region over to east there Mississippi Alabama . Gfs has slp further north. Wouldn’t be suprise southern section Tennessee even.
I think the risk extends to the Kentucky state line on Monday. The GFS was the only one not getting the warm sector that far north, and it has now caved for more than one run.
 

Austin Dawg

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I think the risk extends to the Kentucky state line on Monday. The GFS was the only one not getting the warm sector that far north, and it has now caved for more than one run.
Our local forecast has dropped the 50's highs and 30-40's lows for 60's and 70's highs for the coming week. I don't know how much that might affect this system but when we move to that weather this early it tends to help trigger any storm system especially if it's still cold north of Texas
 

Fred Gossage

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Matt Grantham's morning AFD at BMX echoes the caveats with this setup well, especially for his CWA and for neighboring JAN. Height falls and slight anticyclonic flow aloft will be a big problem for central Alabama and Mississippi in what is an otherwise supportive parameter space. It's not the most alarming parameter space by any remote stretch, but it is supportive. That 573dm line at 500mb across central Alabama doesn't move on Monday. In central Alabama and Mississippi, with that in mind and the shortwave so far north, there will be a lack of large scale ascent to work on the capping associated with the elevated mixed layer. IF a storm were to be able to form on a boundary, it would have a parameter space to work with, but we've had many events over the years like that completely fail.

HOWEVER, once you go farther to the north a bit, you start to get 30-40 meter height falls per 6 hours over the HUN CWA. That area also will have low-level boundaries to work with and will be located closer to the surface low (better low-level convergence). The general region near and north of Highway 278 will also be situated in some subtle but noticeable diffluence in the mid/upper levels between the straight mid/upper jet centered over northern middle TN and northward and the slightly anticyclonically curved jet streak situated from central Alabama back into southern LA, and will actually be near the left front quad of the southern jet near midday. They are subtle, but there are lifting and forcing mechanisms once you get northward into the HUN, MEG, and OHX CWAs. I think there may be a focused corridor Monday from northern or northeastern Mississippi, across northern/northwestern Alabama, up into middle Tennessee, where we are able to trigger a few storms that can take advantage of a supportive (not alarming but supportive) parameter space. And in fact, even a few of the non-CAMs that have okay grid resolution develop a few discrete looking convective elements that track across these areas between 18-00z. I think the general threat is roughly from U.S. 278 in AL/MS northward into however deep into TN the instability ends up going. As of right now, I'd think that would be at least up to U.S. 412.
 

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I am concerned about north Texas with some of the parameters showing up. I think we will have a better picture tomorrow as to how it could evolve. Looks like there could be a cap in place but will it hold?
I am honestly pretty surprised SPC removed the slight risk...NWS Ft Worth posted this earlier.

 

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Yeah I'm struggling to see this one do much at this point in the game. The anticyclonic flow issues are actually getting worse on successive model runs as they catch up to the strength and positioning of the ridge.

Everything else about this system looks solid, but I honestly can't think of a single system off the top of my head that had such stout anticyclonic flow that wasn't a dud, at least when including the context of a Dixie system early in the year.

The -NAO needs to wane some in order for systems to really start capitalizing on the background environment which will probably start coming around in February, but it's still too early in the game right now for this one to really take off on a major level.
 

rolltide_130

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You can see it just by comparing a couple Euro runs.. this is not the same system it was when I first started this thread:

0z Monday run
1611348421760.png

12z today run:

1611348452377.png

The ridge axis which was initially off the coast is now over Washington DC, and what was initially a potent trough is now moreso just a sheared out wave.

It's subtle features like these which are the difference between an outbreak and a non-event.. if the ridge axis stayed where it initially was projected to be a few days ago, the alarm bells would be sounding to their full effect right now.
 

Fred Gossage

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That's not what it looked like when you first started this thread either, and on the very same model you're highlighting there...

1611349067133.png
It was on its way to being a sheared out wave, even then. It still had the slightest bend in the flow, but it was already flattening out. I think the parameter space in over 90% (maybe as much as 95% or more) of the warm sector goes completely to waste because of the lack of better forcing. I'm just concerned that north of the axis of the southern jet streak, where there are 30-50m per 6 hour height falls and you can see the large scale ascent with time on the soundings as the EML is lifted vertically and the cap associated with it then weakens and erodes... there may be one or two storms to try to take advantage of the parameters. There will be low-level boundaries to work with there too. All it takes is one or maybe two. I highly doubt there will be zero storms ahead of the front Monday. But a much smaller scaled, lowered ceiling, and very conditional risk... I'd very much agree that it has definitely trended to that... but it hasn't trended to a complete dud or no risk at all.
 

Taylor Campbell

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I noticed signs of what appeared to be a discrete and potentially tornadic storm in northern MS moving into TN mid Monday morning on the 12z EURO.
 
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Fred Gossage

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The shortwave has not only gotten a bit flatter still than it was yesterday in the data that's come in overnight, but it's shifted a bit more to the northwest than it already was. This has allowed that anticyclonic flow to expand even farther north than it originally was. There had been at least 30-50 meter height falls that would interact with the instability axis, and you could see the cap with the EML lift and disappear with time on the soundings. That's no longer the case. Now, the cold front is also slowing. It looks like it doesn't even arrive into far northwest Alabama until near or after 10pm on Monday. The large scale ascent wasn't previously zero, but it was subtle... but it was doable because we had low-level convergence with the approaching cold front at the same time. Those two have now gotten separated in both time and space by quite a bit.
 

Fred Gossage

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This is the second convective associated system now that's had a northwest trend as we get closer. We're apparently back to the classic slower and northwest trends with time that many of us "grew up with" on this forum over the years. Going forward, ensembles are likely to have the general right idea, but it's the ones on the operational models that appear either too sharp with the trough and/or the system is too far south that we will have to watch vigilantly.

This Monday one, Matt G. and Jonathan B. have called this one accurately. Lack of better large scale ascent is going to cause a mostly wasted warm sector.
 

rolltide_130

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I do still think that tomorrow across TX and NE into SE OK/NW AR could be a potentially active event. It's just not going to translate very well eastward at this point in the game.

A lot of the ingredients this trough has (Cold UL temperatures, strong EML advection, etc) are going to be present for the majority of systems this spring.. it's just a matter of when does the -NAO and undercutting troughs in the Atlantic diminish and allow these systems to translate further east without getting sheared apart? I imagine by the latter half of February we'll start to see signs of that beginning to occur as we begin to transition into spring.
 

Fred Gossage

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I do still think that tomorrow across TX and NE into SE OK/NW AR could be a potentially active event. It's just not going to translate very well eastward at this point in the game.

A lot of the ingredients this trough has (Cold UL temperatures, strong EML advection, etc) are going to be present for the majority of systems this spring.. it's just a matter of when does the -NAO and undercutting troughs in the Atlantic diminish and allow these systems to translate further east without getting sheared apart? I imagine by the latter half of February we'll start to see signs of that beginning to occur as we begin to transition into spring.
That may be happening early month if some of the latest guidance has the right idea bout Canada over to Greenland and then how the polar jet plays out. We're starting the breakdown of the -NAO now by pinching off that ridge over Greenland and retrograding it into Canada. It dies with time from there. By 10 days from now, all blocking is gone, and the Pacific jet is showing its @$$....

1611432791291.png

There's a primer wave in the center of the nation that will eject out so that it doesn't scour Gulf moisture, and behind it is the system around the 4th-5th that a lot of the models, ensembles, CFS, and CIPS are starting to scream about. I don't think this is the start of THE spring action, but this may be a good early preview if there are no big changes to that blocking going away.
 

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