Severe WX May 2019 Plains Severe Event

[warneagle]

Unlike the severe threat, the high risk of excessive rainfall was very accurate.

 

[Equus]

There's a 10% tor today... it honestly wouldn't take too much to surpass yesterday's numbers if we have a QLCS outbreak.

 

[JayF]

 

[Equus]

Looking back at the 2017 high risks... we aren't THAT far below most recent high risk tornado reports with yesterday. Should be more than 20. The difference is, most of them yesterday were outside the high risk. Sure, we had the potentially high end Mangum tornado and the gorgeous twins N of El Reno, which... would verify a slight at best. If not for the 45% and insane watch probs, this wouldn't have been quite as amazing a bust. As it stands it's the biggest 45%+ bust ever. With tornadoes from AZ to MO, some significant, it would've been quite the ENH outbreak, but still underwhelming even for a 30% day.

Of course, if the Mangum tornado is rated EF3 or higher, which is possible, that's actually one of the stronger tors we will have seen in our recent underwhelming high risks. The previous THREE highs didn't manage more than an EF2. Which may say a lot about either construction quality OR the events themselves.

 

[DaveFromGA]

Looking back at the 2017 high risks... we aren't THAT far below most recent high risk tornado reports with yesterday. Should be more than 20. The difference is, most of them yesterday were outside the high risk. Sure, we had the potentially high end Mangum tornado and the gorgeous twins N of El Reno, which... would verify a slight at best. If not for the 45% and insane watch probs, this wouldn't have been quite as amazing a bust. As it stands it's the biggest 45%+ bust ever. With tornadoes from AZ to MO, some significant, it would've been quite the ENH outbreak, but still underwhelming even for a 30% day.

Of course, if the Mangum tornado is rated EF3 or higher, which is possible, that's actually one of the stronger tors we will have seen in our recent underwhelming high risks. The previous THREE highs didn't manage more than an EF2.

I wonder if we will ever see a high risk again. I know the HRRR model was off, was there a model that nailed what actually happened or were they all off?

 

[Evan]

Looking back at the 2017 high risks... we aren't THAT far below most recent high risk tornado reports with yesterday. Should be more than 20. The difference is, most of them yesterday were outside the high risk. Sure, we had the potentially high end Mangum tornado and the gorgeous twins N of El Reno, which... would verify a slight at best. If not for the 45% and insane watch probs, this wouldn't have been quite as amazing a bust. As it stands it's the biggest 45%+ bust ever. With tornadoes from AZ to MO, some significant, it would've been quite the ENH outbreak, but still underwhelming even for a 30% day.

Of course, if the Mangum tornado is rated EF3 or higher, which is possible, that's actually one of the stronger tors we will have seen in our recent underwhelming high risks. The previous THREE highs didn't manage more than an EF2. Which may say a lot about either construction quality OR the events themselves.

I believe that the probabilities of the PDS TOR watch also busted badly being that PDS TOR Watch 199 was only the second time in history that 95%+ probs were assigned to every single parameter listed in the watch outline. 4/27/11 is the only other example, and obviously yesterday busted hard compared to that.

 

[Timhsv]

I'm just speculating from what I saw model wise and from 3 days prior of forecast soundings. None showed much if any CIN or Capping, especially across the HIGH RISK area. It may have been hidden in one or two models I didn't observe, but the CAP from 00Z21 last night showed the obvious at just above 700mb....The Tornado killer.
Of coarse the outflow from the northern line undercut a lot of the southern cells it looked like as well.

Mother Nature in the end does what she wants..as usual.

 

[bwalk]

It's good to know the only things "gone" in Leach are a few "chicken coops". That kind of emotion-based, knee-jerk false information from some people (ie, saying an entire town/community is "gone") is terribly irresponsible and upsetting to family and friends who might hear it.

 

[Equus]

I think every probability in the watch busted hard, for wind hail AND tornadoes. It's wild that seemingly subtle features can override multiple absurdly volatile parameters but that's the way it goes.

 

[bwalk]

The CAP issue yesterday was not always as clear as it seems now in retrospect. The 5/20 18z sounding for Norman yesterday does not show a major cap concern at the 500/700mb like the later(5/21 00z) sounding showed (see Post 485 on this thread). Chasers were already out in the field based on the 18z sounding. By the time the 5/21 00z sounding came out no one was paying much attention. Or, if they were, they interpreted the stronger cap as a good thing, believing it would soon break in a powerful way.

 

[warneagle]

I think the analysis of what the cap meant for the forecast may have been the result of confirmation bias—the assumption was that the main failure mode would be too many storms forming, not too few, so people took the stronger cap to mean that the main failure mode had been eliminated rather than seeing it as a potential failure mode in its own right. It didn’t help that none of the models really forecast a cap of that strength and that it wasn’t obvious in the early observations, but I think there was that preconceived idea of what a stronger-than-expected cap would mean.

I feel like there’s probably a debate to be had about over-reliance on CAMs and the tendency of social media to create feedback loops and promote groupthink as well, but that struck me as the most obvious issue with the nowcasting yesterday evening.

I don’t think they were wrong to go with the high risk given the model output and observed conditions yesterday, but I do think they may have communicated more confidence in the forecast than was actually realistic (particularly in the extreme probabilities in the two PDS watches). You’re never going to get it 100% right and you’ll inevitably be criticized whether your forecast underperforms or overperforms, but being transparent about uncertainty and communicating the level of confidence accurately takes some of the sting out of those criticisms. Hopefully this will be a learning experience both scientifically (still mind-blowing that a day with those parameters busted) and in terms of communication/public relations.

 

[bwalk]

Re my last post above (#530)

Put another way, you had A vs. B

A: B:

 

[South AL Wx]

Also, with the comparison of outlooks/PDS watch probs between 4/27/2011 and yesterday, the 45% tornado contour was actually a bit larger in the 1630z SPC outlook for yesterday compared to the same outlook from 4/27/2011. I'm not sure what exactly to make out of that, but it is an interesting comparison and interesting to look at.

5/20/2019:

4/27/2011:

 

[bwalk]

I think the analysis of what the cap meant for the forecast may have been the result of confirmation bias—the assumption was that the main failure mode would be too many storms forming, not too few, so people took the stronger cap to mean that the main failure mode had been eliminated rather than seeing it as a potential failure mode in its own right. It didn’t help that none of the models really forecast a cap of that strength and that it wasn’t obvious in the early observations, but I think there was that preconceived idea of what a stronger-than-expected cap would mean.

I feel like there’s probably a debate to be had about over-reliance on CAMs and the tendency of social media to create feedback loops and promote groupthink as well, but that struck me as the most obvious issue with the nowcasting yesterday evening.

I don’t think they were wrong to go with the high risk given the model output and observed conditions yesterday, but I do think they may have communicated more confidence in the forecast than was actually realistic (particularly in the extreme probabilities in the two PDS watches). You’re never going to get it 100% right and you’ll inevitably be criticized whether your forecast underperforms or overperforms, but being transparent about uncertainty and communicating the level of confidence accurately takes some of the sting out of those criticisms. Hopefully this will be a learning experience both scientifically (still mind-blowing that a day with those parameters busted) and in terms of communication/public relations.

Some very valid points. We tend to see/believe what we want to see, whether true or not. When others around us "see" the same thing it only strengthens our bias. Mix in a strong dose of excitement, desire & hype and we can become all the more blinded to common sense.

 

[Equus]

Ha yeah that was my line of thought when the cap came in way stronger than the nonexistence that was expected. "Stuff is gonna explode even worse now when it gets going. When it gets going. Aaaaany time now..."

I admit I was quite wrong and put more reliance into the CAMs than the subtleties in the observed soundings. With other parameters that extreme, the crappy lapse rates and capping just didn't come to mind.

 

[tennessee storm chaser]

You just about got to have a decent cap to have a good severe outbreak ... for explosive development when thel lid comes off... but this situation was different ... all the layers were just to warm... which kept the cap to strong to pop .... guess something to watch during future events

 

[Timhsv]

Also, with the comparison of outlooks/PDS watch probs between 4/27/2011 and yesterday, the 45% tornado contour was actually a bit larger in the 1630z SPC outlook for yesterday compared to the same outlook from 4/27/2011. I'm not sure what exactly to make out of that, but it is an interesting comparison and interesting to look at.

5/20/2019:

4/27/2011:

And I'm drawing on recall instead of looking back, but I think the increase came even later at 1630 outlook and was "increased" from 30 to 45% at that point. Kinda of a head scratchier is all. A lot of weight was carried out with that High Risk on Monday and it carried a lot of social impact.
Its just a hard call I know some days when everything that was there model wise sits in front of you and knowing the responsibility falls back on you as a forecaster.

 

[SilentShadow87]

While this definitely was a bust, I wouldn't call it the worst bust ever by a long shot. That title has to go to April 11, 2005.

High risk with 35% hatched risk of tornadoes, above the minimum threshold. Two unconfirmed tornado reports, neither in the high risk area. Very few wind reports, almost none in the high risk area, and no hail reports in the high risk area at all. Reports for the day here.

 

[Dtjet]

 

[Dtjet]

View attachment 1729

Nearly 50 Million People Under Threat of Severe Weather 21st Through 26th. Severe Thunder Storms, Damaging Winds, Flooding, and Isolated Tornados and Severe Hail, Can Not Be Ruled out. These Storms Have Strawn out some very strong Tornados in the passed hours. I urge everyone whom lives in the above States To Be Planning Their Safe Shelters Now. ( STAY SAFE )