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Severe WX Severe Risk 2/23-2/24 (1 Viewer)


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331
Location
Madison, WI
I think there's a major tendency to place the highest risk too far N and W in Dixie events. Convection always seems to cut off that part, or it initiates late. Parameters may be maxed there, but that doesn't always translate to maximum storm coverage.

We have a confirmed EF2 already and Columbus will almost certainly be EF2 (or 3) also, so that's multiple significant tornadoes... ENH would've certainly covered it but there have been worse underperformers. That said, much of the MDT barely even saw rain.
A couple of posts here and on other forums mentioned concerns with the wind fields WRT mesocyclone establishment/longevity...and that's pretty much what happened apart from the Columbus storm. IMO that's one thing that should give the SPC more pause when upgrading to a 15 hatched MDT, especially in cool season events when instability is less than ideal. In retrospect a 10% hatched ENH with mention of "one or two strong tornadoes" would have been just about right. They DID hold off on PDS wording the watch.

The big question for me is WHY were there wind field issues with this event? We had a powerhouse negatively-tilted trough and a rapidly deepening surface low-two elements which have been MIA for most of this decade. Those things tell me wind fields/shear should NOT be an issue.
 

KoD

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Maybe you could start a post mordem thread specifically for this event and have that discussion. Hopefully others will chime in. I won't because I'd have nothing to add but if there is enough participation it will be an interesting and educational read.

If it works out then maybe it can become a thing for major weather events here.
That's a great idea! I'll be sure to do this for the next big weather thread
 

rolltide_130

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I actually did some post-event analysis, and in the vicinity of the Columbus and Burnsville area, wind fields were NOT an issue. In fact, they were better than modeled with slightly lower anvil flow and critical angles in the 60-70 degree range. Also, sfc winds were more backed in this region.

What WAS an issue further west was underforecasted STJ influence, which has been a common theme the last few years, particularly when we combine the background PDO state and El Nino. This is what led to more southerly mid-level flow in our more western soundings, and the influence fired off a big messy wad of convection ahead of schedule by about two hours. It managed to clean out somewhat as it got to E MS and produce a fairly strong event still, but not quite the discrete supercell activity some models had projected.

If it wasn't for this STJ influence, our wind fields would have been pristine across the whole sector, the EML would have been stronger and storm mode would have been discrete. With the very high thermos for February, the STJ likely prevented a high-end outbreak and kept it a little more regional.

Put this in April where STJ influence dies down some, and this same trough likely produces more than one violent tornado..
 

warneagle

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I actually did some post-event analysis, and in the vicinity of the Columbus and Burnsville area, wind fields were NOT an issue. In fact, they were better than modeled with slightly lower anvil flow and critical angles in the 60-70 degree range. Also, sfc winds were more backed in this region.

What WAS an issue further west was underforecasted STJ influence, which has been a common theme the last few years, particularly when we combine the background PDO state and El Nino. This is what led to more southerly mid-level flow in our more western soundings, and the influence fired off a big messy wad of convection ahead of schedule by about two hours. It managed to clean out somewhat as it got to E MS and produce a fairly strong event still, but not quite the discrete supercell activity some models had projected.

If it wasn't for this STJ influence, our wind fields would have been pristine across the whole sector, the EML would have been stronger and storm mode would have been discrete. With the very high thermos for February, the STJ likely prevented a high-end outbreak and kept it a little more regional.

Put this in April where STJ influence dies down some, and this same trough likely produces more than one violent tornado..
I’d be interested to see a comparison of this with the 3/19/18 event (or non-event as it were) because the exact same thing happened in that case—a big blob of messy convection formed right at the start of the window for the event and we never got the discrete supercells despite incredibly strong low-level wind fields. I wonder if that might have been a case of the same sort of problem?
 

rolltide_130

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I’d be interested to see a comparison of this with the 3/19/18 event (or non-event as it were) because the exact same thing happened in that case—a big blob of messy convection formed right at the start of the window for the event and we never got the discrete supercells despite incredibly strong low-level wind fields. I wonder if that might have been a case of the same sort of problem?
Well 3/19 was a little bit of a different issue. The trough itself on 3/19 was smaller scale and didn't really have the energy. Why we got the big blob that day was the trough was SO subtle and weak that the forcing mechanism (a dryline in MS) was titled sideways due to the trough not being dynamically strong enough to orient it N-S.

In this event, we had the trough but an impulse from the STJ got pulled up into it because it's been very highly active due to the nino. Had the impulse not been there, we would have been much higher-end.

In layman's terms, 3/19 didnt go high-end due to synoptic scale issues. Saturday didn't due to mesoscale issues.
 

Wyldeweather63

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I actually did some post-event analysis, and in the vicinity of the Columbus and Burnsville area, wind fields were NOT an issue. In fact, they were better than modeled with slightly lower anvil flow and critical angles in the 60-70 degree range. Also, sfc winds were more backed in this region.

What WAS an issue further west was underforecasted STJ influence, which has been a common theme the last few years, particularly when we combine the background PDO state and El Nino. This is what led to more southerly mid-level flow in our more western soundings, and the influence fired off a big messy wad of convection ahead of schedule by about two hours. It managed to clean out somewhat as it got to E MS and produce a fairly strong event still, but not quite the discrete supercell activity some models had projected.

If it wasn't for this STJ influence, our wind fields would have been pristine across the whole sector, the EML would have been stronger and storm mode would have been discrete. With the very high thermos for February, the STJ likely prevented a high-end outbreak and kept it a little more regional.

Put this in April where STJ influence dies down some, and this same trough likely produces more than one violent tornado..
Good work. The only way to get better is by learning from the past. So many people just want to jump to the next potential threat without trying to understand what went right/wrong with the last system. Anybody can overhype a threat (Reed Timmer).
 
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Kory

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Tuscaloosa, Alabama
I actually did some post-event analysis, and in the vicinity of the Columbus and Burnsville area, wind fields were NOT an issue. In fact, they were better than modeled with slightly lower anvil flow and critical angles in the 60-70 degree range. Also, sfc winds were more backed in this region.

What WAS an issue further west was underforecasted STJ influence, which has been a common theme the last few years, particularly when we combine the background PDO state and El Nino. This is what led to more southerly mid-level flow in our more western soundings, and the influence fired off a big messy wad of convection ahead of schedule by about two hours. It managed to clean out somewhat as it got to E MS and produce a fairly strong event still, but not quite the discrete supercell activity some models had projected.

If it wasn't for this STJ influence, our wind fields would have been pristine across the whole sector, the EML would have been stronger and storm mode would have been discrete. With the very high thermos for February, the STJ likely prevented a high-end outbreak and kept it a little more regional.

Put this in April where STJ influence dies down some, and this same trough likely produces more than one violent tornado..
April 24, 2010 shows you can still get an outbreak with long track/violent tornadoes with subtropical jet disturbance. If I remember correctly, there was a lot of convection prior to the afternoon tornadoes in AL.
 
Messages
331
Location
Madison, WI
April 24, 2010 shows you can still get an outbreak with long track/violent tornadoes with subtropical jet disturbance. If I remember correctly, there was a lot of convection prior to the afternoon tornadoes in AL.
The Yazoo City tornado that day was practically in a class by itself at the time. I believe its DPI (Destruction Potential Index, some algorithm combining intensity and path length/width) was greater than that of some entire outbreaks. The lead-up to that day also had some of the most ominously-worded outlooks and forecast discussions I'd ever seen. Then came a year and three days later....
 
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387
Location
Niagara Falls, Ontario
The Yazoo City tornado that day was practically in a class by itself at the time. I believe its DPI (Destruction Potential Index, some algorithm combining intensity and path length/width) was greater than that of some entire outbreaks. The lead-up to that day also had some of the most ominously-worded outlooks and forecast discussions I'd ever seen. Then came a year and three days later....
Yeah I think you can easily talk about Yazoo City and Hackleburg in the same breath. Apparently the Yazoo City tornado had one of the most impressive radar signatures and rotational energy ever seen, and some of the tree and vegetation damage was absolutely insane. Honestly it's lucky that a good two thirds of its path was through forests. Put it through a town while it was at peak strength and I'm guessing the death toll would probably have at least tripled.

Another one that had an unbelievable radar signature at times but just didn't hit much was the Rose Hill/Enterprise EF4 on April 27. It was pretty much missed by most people since all eyes were on Tuscaloosa at the time but I personally think it was at least as violent, even if it only did a fraction of the damage.

As for Saturday, I wouldn't personally call it a bust - an underperformer, maybe. But we now have three confirmed EF2+ tornadoes, which is pretty intense by the standard of the last couple of years. This is also just my opinion and probably a bit non-objective, but someone was killed on Saturday, and calling any event where there was any loss of life a "bust" feels disrespectful. The death toll could have been higher if people were not on alert.
 

warneagle

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Yazoo City was incredible. It was like some of those tornadoes described in the pre-modern outbreaks that allegedly tracked >100 miles except we can verify that it actually did that. I’m sure it would’ve been an EF-5 had it hit enough substantial structures at peak intensity (although it thankfully didn’t as the damage was bad enough as it was). It probably never reached the top-end strength of the Hackleburg/Phil Campbell tornado but it’s definitely in the same category in terms of maintaining great intensity for an incredibly long time.
 

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