Severe WX Severe Threat 25 March 2021

[Shakespeare 2016]

The EF4 rating seems surprisingly liberal. Definitely not second guessing FFC as it probably deserves it but from damage I've seen I'd not be shocked if that would've peaked at high EF3 in some WFOs. Kind of like Hattiesburg 2013 and Dayton 2019.

I think the rating for the Rozel, KS 2013 tornado was over lenient. Not even the contextual evidence could convince me of a rating higher than low-end EF3. However, their experts so who am I to question them.

 

[Equus]

Was Rozel one of the ones that got bumped to EF4 due to DOW measurements or were there supposedly EF4 DIs? I think I remember only seeing EF3 damage and getting bumped later but that's been a while and I forget.

 

[WhirlingWx]

I do think it's problematic that two straight highs in Mississippi produced virtually nothing there and it would be nice to get some research into why modeling was a swing and a miss both times; there will certainly be some big time complacency across MS and parts of north AL next time because two straight events passed without significant severe in either place.

If we apply the 10000% totally accurate method of predicting the most severe reports being southeast of the SPC's bullseye, MS and north AL will get their turn tomorrow /s

But in all seriousness, I agree. The placement of the high risk areas at the time seemed perfectly logical based on modeling and environment at the time, yet the atmosphere had other ideas, as we all know.

 

[buckeye05]

There was ground level footage to show these debris really churn into very Small peices and carried very long distance.

Ok yeah, that’s legit debris granulation. Or “match-sticking” as another poster called it. I kinda like that term. Definitely descriptive and accurate.

 

[pohnpei]

I do think it's problematic that two straight highs in Mississippi produced virtually nothing there and it would be nice to get some research into why modeling was a swing and a miss both times; there will certainly be some big time complacency across MS and parts of north AL next time because two straight events passed without significant severe in either place.

What I notcie for yesterday in MS was that CAMs really downtrended the sfc low and LLJ in entire MS a lot after 6z, especially after 12z. So with very impressive CAPE but relatively weak dynamic condition, it was no surprising that MS performed below expectation yesterday. That to tell us need to watch CAMs really closely at short term not just oberservation sounding in the morning.

 

[pohnpei]

Was Rozel one of the ones that got bumped to EF4 due to DOW measurements or were there supposedly EF4 DIs? I think I remember only seeing EF3 damage and getting bumped later but that's been a while and I forget.

Yes, the structure damage of Rozel was just EF2 level.

 

[Equus]

If we apply the 10000% totally accurate method of the most severe reports being southeast of the SPC's bullseye, MS and north AL will get their turn tomorrow /s

But in all seriousness, I agree. The placement of the high risk areas at the time seemed perfectly logical based on modeling and environment at the time, yet the atmosphere had other ideas, as we all know.

Yeah the super frustrating thing is that based on modeling and parameters, those areas pretty much had to be put in the highest risk, and both times last minute factors mitigated the risk. It really looks bad on verification despite sparing the high risk areas

 

[Equus]

Yes, the structure damage of Rozel was just EF2 level.

Ok yeah that's what I thought. The annoying thing is certain tornadoes in that time period were rated based on DOW and then others (El Reno mainly) were explicitly downgraded despite DOW measurements, leading to an INCREDIBLE rating inconsistency WFO to WFO in 2013. Getting off topic, but yeah that issue still hasn't been corrected and the ratings from mid 2013 are still weirdly skewed.

 

[WhirlingWx]

What I notcie for yesterday in MS was that CAMs really downtrended the sfc low and LLJ in entire MS a lot after 6z, especially after 12z. So with very impressive CAPE but relatively weak dynamic condition, it was no surprising that MS performed below expectation yesterday. That to tell us need to watch CAMs really closely at short term not just oberservation sounding in the morning.

Definitely agree about the sfc low intensity, people who are much smarter than me were the first to point it out, but by mid-afternoon, seeing the surface low pretty weak and disorganized when we were initially expecting it to go ~995 mb or lower was kind of a sign to me that things weren't really going exactly as planned. Pretty sure the Euro got it down to like 982 mb for a run that was like only a couple days prior to the event. Obviously, central AL was doing its thing by the afternoon but for the areas with "higher" risk, the wind fields just got a little junky for a while. Even when the wind fields recovered a bit later on, the cap was pretty stout in MS and still kept things quieter there.

 

[WhirlingWx]

Or “match-sticking” as another poster called it. I kinda like that term. Definitely descriptive and accurate.

I second this. @CheeselandSkies was the one who said it, I believe.

 

[buckeye05]

Yes, the structure damage of Rozel was just EF2 level.

Yes! I remember they actually retained the EF4 rating by claiming that a house which sustained partial roof and wall loss sustained “low-end EF4” damage. It was clear to me that they just used that house as a damage point to apply an utterly absurd EF4 rating to, so that higher ups couldn’t force them to downgrade, since they initially assigned the EF4 rating based on mobile radar wind speed measurements. If they have a structure damage basis for the rating, they don’t have to downgrade.

Clearly, this tactic worked, but it’s extremely obvious that the survey team pulled some total bs to keep it at EF4.

 

[TH2002]

Yes! I remember they actually retained the EF4 rating by claiming that a house which sustained partial roof and wall loss sustained “low-end EF4” damage. It was clear to me that they just used that house as a damage point to apply an utterly absurd EF4 rating to, so that higher ups couldn’t force them to downgrade, since they initially assigned the EF4 rating based on mobile radar wind speed measurements. If they have a structure damage basis for the rating, they don’t have to downgrade.

Clearly, this tactic worked, but it’s extremely obvious that the survey team pulled some total bs to keep it at EF4.

What did the NWS have to gain from keeping the rating at EF4 though? Clearly Rozel definitely didn't warrant an EF4 rating though why would they insist on keeping that rating?

 

[Equus]

Prolly the same reason DDC took so long to survey the no tornado and LZK defended Vilonia to the point of absurdity

 

[Shakespeare 2016]

What did the NWS have to gain from keeping the rating at EF4 though? Clearly Rozel definitely didn't warrant an EF4 rating though why would they insist on keeping that rating?

That is what I would like to know as the house level damage was no more than a high-end EF2. I said low-end EF3 based on some contextual damage and I feel like that would be pretty lenient as well.

 

[Shakespeare 2016]

Prolly the same reason DDC took so long to survey the no tornado and LZK defended Vilonia to the point of absurdity

Vilonia was also pure bs as well.

 

[Matthew70]

I do think it's problematic that two straight highs in Mississippi produced virtually nothing there and it would be nice to get some research into why modeling was a swing and a miss both times; there will certainly be some big time complacency across MS and parts of north AL next time because two straight events passed without significant severe in either place.

With yesterday's event, it's looking like a much weaker shortwave than expected (leading to SW surface winds parallel to storm motion and thus rapid upscale growth until late in the afternoon) was one of the big issues; in AL, that massive rain shield really killed the instability since the very strong EML that moved in behind the mass could not be overcome with the much lower level of instability that resulted, capping off the second round. The open warm sector wherever storms weren't blobbed up together clearly produced violent sustained cells, but the ingredients just didn't come together across N MS and most of NW AL, again.

Memphis also included. There has not been a single tornado warning in a moderate and high risk last 2 weeks.

 

[TH2002]

Prolly the same reason DDC took so long to survey the no tornado and LZK defended Vilonia to the point of absurdity

Vilonia was also pure bs as well.

I have a feeling that LZK received some fat checks from Arkansas politicians to keep the rating at EF4.

 

[Shakespeare 2016]

I have a feeling that LZK received some fat checks from Arkansas politicians to keep the rating at EF4.

https://en.m.wikipedia.org/wiki/Tornado_outbreak_of_May_18–21,_2013#/media/File:May_18,_2013_Rozel,_Kansas_tornado_damage.jpg
Sorry I know this has nothing to do with Vilonia but you see the absurdity of the EF4 rating for the Rozel 2013 tornado.

 

[TH2002]

https://en.m.wikipedia.org/wiki/Tornado_outbreak_of_May_18–21,_2013#/media/File:May_18,_2013_Rozel,_Kansas_tornado_damage.jpg
Sorry I know this has nothing to do with Vilonia but you see the absurdity of the EF4 rating for the Rozel 2013 tornado.

Yeah that structural damage is nowhere near worthy of an EF4 rating. I suppose the propane tank being thrown .25 miles and is fairly impressive though nothing an EF3 couldn't cause? I also read that the tornado scoured a dirt road though some EF3's have produced ground scouring. Definitely not EF4 worthy though.

 

[Equus]

A few notes from various drone footage along the big wedge path... am not seeing many frame homes with much damage, mostly mobile homes thrown off their blocks, but there are a couple other interesting instances of damage

Multiple transmission towers were broken near Greensboro



Swath of near 100% softwood snapping, indicative of at least low end EF3 intensity (have seen tornadoes rated low EF3 for this degree of tree snapping)



And finally... look how close it got to the former NWS radar site, which was hit and destroyed on 5/27/73