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Severe Weather Threat 5/25-5/26, 2024

Fred Gossage said:
Tomorrow is one of the events that argues that, as long as we're confident that the low number of storms won't end up being only one singular storm, there doesn't need to be so much focus on having a swarm of violent EF4+ tornadoes in order to trigger a High Risk. If that's the way things are going to be handled from here on out (needing a swarm of violent tornadoes for a High Risk, that is), it's an intentional breaking of the climatology of the convective outlook system that's been in place since before I was born. Going all the way back to the initial inception of those categories in 1982, it was never intended to be that way. Days where there ends up being a handful of smaller tornadoes alongside one or two that are full-blown violent EF4-EF5 should constitute a "lower-end" High Risk (it always did from 1982-2014 at least), and I have a feeling tomorrow in Oklahoma may show you why that's the case.
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Guess we know what @Fred Gossage thinks of tomorrow. Hehe
 
KCweatherboy said:
I wouldn't say it's been a long time. The type of outbreaks you've always talked about only happen once in a blue moon. The last ones being 5/24/11, 5/3/99, and 4/26/91. Before that though, you could argue you have to go back to 1955 to find that level of an outbreak (unless I'm missing one) in Oklahoma. There is going to be a natural variance in the duration between outbreaks simply due to statistics, and it's certainly possible that having 3 events as large as those in the past 30 years is a statistical anomaly.
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You're missing 8/6/74, which was larger than 25/4/55 (and larger than 26/4/91 in Oklahoma). And if 25/5/55 is your benchmark then there are others such as 10/5/10 and 10/4/79.

The idea the past decade, or at least several years, has been unusually inactive on the plains is a very widespread one so there might be something to it. Though I don't think it's very large outbreaks there's fewer of as IMO they've usually been more of a midwest and south thing, but rather the moderate sized slower moving diurnal outbreaks that the chasers like. But we won't know until someone breaks down the data.
 
Kds86z said:
Guess we know what @Fred Gossage thinks of tomorrow. Hehe
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Press Conference Kermit GIF

Sometimes you have to look past the CAMs that have been falling flat on their faces 0-6 hrs out consistently all week, and take a look back at the synoptics.... and realize that we have a much sharper dryline with better low-level convergence compared to the last HIGH, and instead of having a mid/upper jet that's more meridional to a slanted dryline, we have a jet that punches directly and squarely across the dryline and warm sector. If we would've hung our hats on CAM storm coverage a day ahead of time with 4/14/2012 instead of Rich Thompson seeing the synoptics for what they were, we would've completely missed that day... and there were tornadic supercells that day by 18z.
 
Yeah, with a jet stream this strong going almost perpendicular in orientation relative to the dry line and weak capping, I seriously don’t think I’ve seen the cams this out of touch before.

I’m almost positive we’re going to see more than just one or two storms in Oklahoma tomorrow, if not, I will cut off my hair and eat it like spaghetti. (Edit: sorry if I put unwanted images in the heads of anyone who reads this)
1716590342902.png
 
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Fred Gossage said:
Press Conference Kermit GIF

Sometimes you have to look past the CAMs that have been falling flat on their faces 0-6 hrs out consistently all week, and take a look back at the synoptics.... and realize that we have a much sharper dryline with better low-level convergence compared to the last HIGH, and instead of having a mid/upper jet that's more meridional to a slanted dryline, we have a jet that punches directly and squarely across the dryline and warm sector. If we would've hung our hats on CAM storm coverage a day ahead of time with 4/14/2012 instead of Rich Thompson seeing the synoptics for what they were, we would've completely missed that day... and there were tornadic supercells that day by 18z.
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Wish I remembered that day.. I have tracked tornado events since 2000. Will have to research.
 
@A Guy @CheeselandSkies @KCweatherboy To me a HIGH-Risk Plains outbreak features two or more cyclic, long-lived supercells, three or more EF3+ events, and two or more EF4+ (this may include events that are not officially rated as such*, but are likely capable of EF4+ damage, based on various indicators). That would include many more events, like the following:

1 May 1954
25 May 1955
2 Apr 1956
20 May 1957
5 May 1960
12 Apr 1964
5 May 1964
8 May 1965
8 Jun 1966
8 Jun 1974
6 May 1975
18 Jun 1975*
10 Apr 1979
17 May 1981*
13 Mar 1990
26 Apr 1991
8 Jun 1995
3 May 1999
4 May 2003
4 May 2007*
23 May 2008*
10 May 2010
24 May 2011
14 April 2012*

This is definitely not once in a generation...
 
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A Guy said:
You're missing 8/6/74, which was larger than 25/4/55 (and larger than 26/4/91 in Oklahoma). And if 25/5/55 is your benchmark then there are others such as 10/5/10 and 10/4/79.

The idea the past decade, or at least several years, has been unusually inactive on the plains is a very widespread one so there might be something to it. Though I don't think it's very large outbreaks there's fewer of as IMO they've usually been more of a midwest and south thing, but rather the moderate sized slower moving diurnal outbreaks that the chasers like. But we won't know until someone breaks down the data.
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Those are also great examples, but that still means those type of events are quite rare and relatively infrequent. Statistically, that's quite a small sample size, so I don't think it's possible to determine whether something has fundamentally changed with tornadoes in the plains or whether it's just simply statistical variance within the weather we've observed. Discounting the possibility of future significant events without considering that seems dangerous when lives are at stake.

Tomorrow has the higher-end potential to be at the level of those events, so we as the weather community certainly should be paying attention to it. And say it doesn't reach that potential (and hopefully it doesn't, protecting life and property) that doesn't mean "violent long-track tornado outbreaks" don't happen anymore. Realistically, we still need many more years of data before we can even attempt to make that conclusion.
 
CheeselandSkies said:
April 27, 2011 skewed many perceptions of what a high risk day should be, it was extreme even by the standards of that risk category. However, with the increased rarity (assuming a desire for increased confidence and to reduce the likelihood of a perceived "Forecasted Convective Amplification Deficiency") with which SPC has applied the high risk after 2014 it is quite remarkable that all three issued in the classic "Tornado Alley" Plains region (in May 2017, 2019 and now in 2024) actually have underperformed or by some perceptions "Atmospheric Anti-Climax."

My old interpretation of an "ideal" high risk day in terms of forecast verification was something like Veteran's Day 2002, May 4, 8 and 10, 2003, Super Tuesday 2008 (ironically, a high risk was also put out on May 22nd that year, but it was the following day, IIRC a moderate risk, that produced a truly extraordinary tornado wedge swarm in Kansas that somehow avoided much of any impact on population centers) or April 24 and May 10, 2010.
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Setting the bar for an 'ideal high risk' at Super Tuesday, which had five violent tornadoes and was about the same size as May 3 1999, isn't exactly setting it low. In terms of violent tornadoes the only bigger event recently has been April 27 itself. The other option are more understandable though.

I don't have any problem with the current mainly probabilistic definitions as they're reasonably objective and allow reasonably objective forecast verifications, which is better than the vibes-based arguments that seem to come up.
 
i wonder if i might ask the forum's advice about some outdoor plans i have in Kentucky on Sunday. forgive me if this is not the right place; I'm a casual lurker on several weather forums, but have no real expertise and am struggling to understand the probabilities indicated by the models.

i'm traveling to attend an outdoor performance in Louisville scheduled for 8-11pm Sunday. is it reasonable to think this might still go on? or more likely that the storms will shut it down? i know nothing can be known for certain, but i'd be very happy to hear anyone's thoughts. i am set to fly to Louisville tomorrow morning, but would stay home if the weather was likely to shut down the event. thank you in advance--i have enjoyed learning from you all.
 
Fred Gossage said:
Press Conference Kermit GIF

Sometimes you have to look past the CAMs that have been falling flat on their faces 0-6 hrs out consistently all week, and take a look back at the synoptics.... and realize that we have a much sharper dryline with better low-level convergence compared to the last HIGH, and instead of having a mid/upper jet that's more meridional to a slanted dryline, we have a jet that punches directly and squarely across the dryline and warm sector. If we would've hung our hats on CAM storm coverage a day ahead of time with 4/14/2012 instead of Rich Thompson seeing the synoptics for what they were, we would've completely missed that day... and there were tornadic supercells that day by 18z.
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You mean actually forecasting instead of relying on a convective reflectivity simulation to do it for you!? That’s blasphemous these days!

In all seriousness, CAMs are great for what they are, but they’re a tool, like every model. Actually building a forecast off of the synoptics (knowing mesoscale influences will occur) and what should happen is still the correct approach like Fred concisely said.
 
rainyrally said:
i wonder if i might ask the forum's advice about some outdoor plans i have in Kentucky on Sunday. forgive me if this is not the right place; I'm a casual lurker on several weather forums, but have no real expertise and am struggling to understand the probabilities indicated by the models.

i'm traveling to attend an outdoor performance in Louisville scheduled for 8-11pm Sunday. is it reasonable to think this might still go on? or more likely that the storms will shut it down? i know nothing can be known for certain, but i'd be very happy to hear anyone's thoughts. i am set to fly to Louisville tomorrow morning, but would stay home if the weather was likely to shut down the event. thank you in advance--i have enjoyed learning from you all.
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Welcome! Louisville is in an Enhanced risk (level 3/5) for Sunday, which may increase as the event draws closer. Unfortunately, this means there is a strong possibility the weather will impact your outdoor event.

Nailing down the exact timing and mode of convection at this range is always a dicey proposition, but the few CAM forecasts available out to 60 hours (such as the 18Z 3KM NAM) do depict thunderstorms, potentially severe, in the Louisville area during the timeframe you mentioned.
 
MichelleH said:
Thoughts on Sunday for your coverage area Fred?
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Supercell type tornado threat has trended north of not only my coverage counties, but probably north of the TN/KY line altogether, although it will be a closer call between the state line there and down to I-40. For southern TN, north AL, etc., I see it as an overnight line of storms with mainly wind and localized flooding, but shear profiles will support a few spin-up tornadoes.
 
jiharris0220 said:
Had storms simply remained discrete and lasted into that night, we could’ve had multiple Barnsdall like supercells running down eastern Oklahoma.

It’s seriously eerie how easily that high risk could’ve verified had storms simply remained discrete and low level shear was a bit more veered.
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Isn't that what we're forecasting tomorrow?
 
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