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Severe WX March 23-25th, 2023

I'm thinking a few factors have precluded an upgrade to high risk today, despite the absolutely classic 500mb structure and strong surface mass response with this system.

1.) The area of greatest threat is relatively small - the moderate risk area is about the size of a typical high risk area you'd see on a day like 4/27/11, 3/2/12 or 3/25/21, and the moderate risk would then have to be expanded to surround that, and the relatively high confidence long-track supercell tornado threat just isn't there over that large of an area.

2.) Going along with that, the time window for discrete warm-sector supercell activity is fairly narrow as per the HRRR runs starting this morning. There should still be about a 2-3 hour window, but after that a transition to QLCS/bow echoes is apparent.

3.) It looks like the area with the best window for a discrete mode again will be somewhat displaced from the area with the strongest low-level shear. If there were a strong CAM signal for a discrete supercell riding just ahead of the triple point as the cyclogenesis really ramps up, that would have high potential for a "VVLT" (violent very-long-track) tornado or tornado family in 12/10/21 or 3/18/1925 style given the hodographs on forecast soundings just ahead of the surface low, but most CAMS including the HRRR have a very quick transition to a quasi-linear/messy convective mode there.

Again to reiterate though - just because a threat doesn't reach high risk caliber doesn't make it a Forecasted Convective Amplification Deficiency, and outlook category becomes meaningless when a tornado warning goes out for your location.
 
Looks like everything is linear at the moment.

That can be a bit of a headfake from the atmosphere at times, though. Sometimes a bunch of updrafts will go up as linear bands and it takes a while for them to sort themselves out, and then a dominant supercell quickly evolves out of it and goes bananas. 3/5/22 looked like a convective mess in southwest Iowa at first, then Winterset happened.
 
That can be a bit of a headfake from the atmosphere at times, though. Sometimes a bunch of updrafts will go up as linear bands and it takes a while for them to sort themselves out, and then a dominant supercell quickly evolves out of it and goes bananas. 3/5/22 looked like a convective mess in southwest Iowa at first, then Winterset happened.
Main show won't be towards sunset so definite head fake thus far
 
I'm thinking a few factors have precluded an upgrade to high risk today, despite the absolutely classic 500mb structure and strong surface mass response with this system.

1.) The area of greatest threat is relatively small - the moderate risk area is about the size of a typical high risk area you'd see on a day like 4/27/11, 3/2/12 or 3/25/21, and the moderate risk would then have to be expanded to surround that, and the relatively high confidence long-track supercell tornado threat just isn't there over that large of an area.

2.) Going along with that, the time window for discrete warm-sector supercell activity is fairly narrow as per the HRRR runs starting this morning. There should still be about a 2-3 hour window, but after that a transition to QLCS/bow echoes is apparent.

3.) It looks like the area with the best window for a discrete mode again will be somewhat displaced from the area with the strongest low-level shear. If there were a strong CAM signal for a discrete supercell riding just ahead of the triple point as the cyclogenesis really ramps up, that would have high potential for a "VVLT" (violent very-long-track) tornado or tornado family in 12/10/21 or 3/18/1925 style given the hodographs on forecast soundings just ahead of the surface low, but most CAMS including the HRRR have a very quick transition to a quasi-linear/messy convective mode there.

Again to reiterate though - just because a threat doesn't reach high risk caliber doesn't make it a Forecasted Convective Amplification Deficiency, and outlook category becomes meaningless when a tornado warning goes out for your location.
Agreed. I really think the NWS has grown conservative with their categorical risks(and their surveys haha) over the past few years after some high profile under performers and they want to save those for those high risks on days a high end outbreak is almost a given so the public aren’t desensitized to them.
 


Of special note are multiple bands of convection which are gradually
deepening within the moist plume near the Sabine River. This plume
of 70+ dewpoints is resulting in over 1500 J/kg MLCAPE, which is
sufficient to support supercells as lift continues to increase with
time. While a relative warm layer still exists near 700 mb as can be
seen on the 18Z SHV sounding, the moist layer has already become
deep enough to break the cap, resulting in warm-sector storms well
east of the cold front.

As the low-level jet increases this evening, so will shear and
supercell/tornado potential. Effective SRH on the order of 300 m2/s2
with 0-1 SRH over 200 m2/s2 may support a few strong tornadoes with
maturing cells east of the cold front. As such, a new watch will
likely be needed to include areas east of WW 75.
 
definitely have my eye on those around Winfield. If they keep that space and not congeal they could start tapping into that environment as they track eastward

1679692177255.png
 
Turning very linear across parts of S Louisiana, I wonder if this is going to significantly tamper discrete mode or if a supercell can still emerge from this. Otherwise discrete convection still possible ahead of that line.
 
Turning very linear across parts of S Louisiana, I wonder if this is going to significantly tamper discrete mode or if a supercell can still emerge from this. Otherwise discrete convection still possible ahead of that line.
Yeah so far spacing is…. Not ideal. Or if these lines just swallow anything discrete before they can even get going.
 
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