Severe Weather Threat 4/27-4/28, 2024 - (Saturday, Sunday)

[jiharris0220]

How 'bout these apples?

View attachment 25581

Posting ridiculous soundings unnecessarily adds to the hype train, but sometimes you just got record these for posterity because even if it doesn't verify, you don't see this very often.

EHI of 11+ speaks for itself, although that hodograph is a bit wonky to say the least despite the classic sickle shape.
Obviously this is the nam we’re talking about but overall just more reason to take this upcoming threat seriously.
I’m waiting with bated breath for the hrrr, Fv3, 3km nam, and WRFs to come into range for a higher confidence judgement of the environment before I at least pull the alarm.

 

[jiharris0220]

lolwat
that is a textbook hodograph for a strong/violent tornado

It absolutely is, but the sounding/hodograph is a bit contaminated, (see those red lines on the side?) that means a storm is nearby interfering with the sounding.
That’s what I meant by saying it was wonky. My bad though, definitely should’ve clarified some more.

Edit: to add more info, the red lines that are perpendicular to the omega field indicate vertical velocity, the more extended the red lines, the faster the air is indicated rising.

The DP and TP parcels being right on top of each other means that a sounding is basically inside of storm.

 

[Tempestas Tonitrua]

Contaminated soundings will also supercharge or boost the parameters. EHI values of 11 were what we were actually seeing on 4/27/11.

 

[NorthGaWeather]

Just because X, Y, Z event did whatever previously this year, doesn't mean the next one has to.

Preach brother

 

[JPWX]

I also agree, there seems to be a pretty good model consensus on the shape of the trough and the lack of downtrending too. For example, here's a look comparing models at 18z on Saturday:


View attachment 25573

*NOT TRYING TO FEARMONGER* but seeing the shape of the trough, a few examples jumped out to me which I will share below.

Similar to what Andyhb said with a 50kt LLJ in play by 4pm in the plains, bad things tend to happen. I'd like to add that troughs with this neutral/negative tilt ejecting into the Plains tend to lead to bad things happening too. Based on the models, this trough seems like it will have a neutral/negative tilt. However, mesoscale details obviously still have to perfectly come together as well for supercells and tornadoes to occur.

An example of this would be 5/24/11, however, the trough was more amplified, with a strongly negative tilt. The mesoscale details also seemed perfect for this event but we won't know those until the day of, of course.
View attachment 25575

4/14/12 also had a generally similar trough shape, however, it was a lot more monstrous of a trough than this one and generally had a more positive/neutral tilt to it. Of course, the mesoscale details also aided this event in becoming what it did.
View attachment 25576

And my last example would be the 5/20/19 "bust" which would be an example where the overall trough is very, very impressive, but the mesoscale details did not aid the event in reaching its potential.

View attachment 25577


As modeled this event certainly has potential and warrants the D4 30%, and I personally always like looking at historical analogs to examine the range of possibilities. As many others have mentioned the mesoscale details are yet to be seen, and will play a big role in the outcome of any storms.

Would love to hear other's insights on this!

How did I not know about this website? LOL!

 

[KCweatherboy]

How did I not know about this website? LOL!

It's been super helpful for learning more about the meteorological context behind many events. Highly recommend it!

 

[Timhsv]

How 'bout these apples?

View attachment 25581

Posting ridiculous soundings unnecessarily adds to the hype train, but sometimes you just got record these for posterity because even if it doesn't verify, you don't see this very often.

If all of the parameters and wind fields verified along with that directional shear and 3CAPE at 165 on this sounding, you would be looking at at least an EF4+ strength, violent tornado.

 

[Taylor Campbell]

Thread for Saturday and Sunday’s severe weather threat.

 

[jiharris0220]

Never a good thing to see the linear happy nam actually show a discrete mode.

 

[Fred Gossage]

If I was hypothetically the SPC outlook forecaster early Saturday morning for that Day 1 outlook, and the short-term model data for the coming afternoon and evening was looking like what the GFS was showing 24-48+ hours ago, I would've been drawing a 45% hatched tornado area across central Oklahoma up into south central Kansas. Since then, there's been a shift toward the pieces of energy within the trough being very slightly disjointed and the trough being a bit more meridional. That is today's GFS taking a step toward the Euro and some of the others with the synoptics, and the GFS has always been the most violent looking of the bunch with the Saturday setup. I don't think this trough geometry adjustment precludes a supercell-driven sigtor threat on Saturday by any means, but once you put that synoptic geometry concern with the potential for earlier initiation and how that synoptic geometry may cause adjacent updrafts to rain into each other and maybe somewhat more efficient cold pooling potential from earlier convection before deep-layer shear really increases (which is now delayed slightly with the meridional trough geometry), it's not too hard to see that the ceiling of this event has been walked back a little. I still think it's firmly a Moderate Risk and maybe even PDS watches... and if we can keep storms spaced, it may be capable of more than that... but just 24-36 hours ago, some of the data (and not even considering the NAM from yesterday) had this setup on the same caliber as 5/24/2011 and some of the infamous multiple-F4+ outbreaks of OK/KS from the 1990s. That's not the case anymore.

 

[CheeselandSkies]

He lives! Welcome back, Fred!

 

[Tempestas Tonitrua]

Amazing post Fred. Always glad to have your input on here.

Definetly think a lot of people were guilty, including myself, of getting ahead of themselves with the threat on Saturday. Especially after seeing some of the sounding analogs. I know I did.

But like I said previously, I just can’t see Saturday even coming close to those aforementioned infamous plains events. And it seems the slight walk back by the models would lend credence to that. Messy storm mode, a disjointed trough, and nebulous forcing would certainly temper what was once looking like a high end environment. Conservatism seems to be the right play this year.

 

[NorthGaWeather]

Definetly think a lot of people were guilty, including myself, of getting ahead of themselves with the threat on Saturday. Especially after seeing some of the sounding analogs. I know I did.

I disagree. The potential shown by modeling was given sufficient weight. If anything, there was some doubt cast on the event due to recency bias.

The event still has a very high ceiling and will be modulated by the two things that have always been concerns…early initiation and timing of trough ejection. And those finer details that will make or break this event cannot be resolved this far out with high confidence.

 

[jiharris0220]

Saturday is a high potential day, what Fred was saying is that it no longer looks like it will be a sure fire high risk day where there’s little doubt an outbreak will occur.
Definitely not on the same level of confidence that 90s Oklahoma outbreaks would’ve had, at least not today.

 

[lake.effect]

If I was hypothetically the SPC outlook forecaster early Saturday morning for that Day 1 outlook, and the short-term model data for the coming afternoon and evening was looking like what the GFS was showing 24-48+ hours ago, I would've been drawing a 45% hatched tornado area across central Oklahoma up into south central Kansas. Since then, there's been a shift toward the pieces of energy within the trough being very slightly disjointed and the trough being a bit more meridional. That is today's GFS taking a step toward the Euro and some of the others with the synoptics, and the GFS has always been the most violent looking of the bunch with the Saturday setup. I don't think this trough geometry adjustment precludes a supercell-driven sigtor threat on Saturday by any means, but once you put that synoptic geometry concern with the potential for earlier initiation and how that synoptic geometry may cause adjacent updrafts to rain into each other and maybe somewhat more efficient cold pooling potential from earlier convection before deep-layer shear really increases (which is now delayed slightly with the meridional trough geometry), it's not too hard to see that the ceiling of this event has been walked back a little. I still think it's firmly a Moderate Risk and maybe even PDS watches... and if we can keep storms spaced, it may be capable of more than that... but just 24-36 hours ago, some of the data (and not even considering the NAM from yesterday) had this setup on the same caliber as 5/24/2011 and some of the infamous multiple-F4+ outbreaks of OK/KS from the 1990s. That's not the case anymore.

And this is why you get paid to do this while the rest of us are just watching

 

[Tempestas Tonitrua]

I disagree. The potential shown by modeling was given sufficient weight. If anything, there was some doubt cast on the event due to recency bias.

The event still has a very high ceiling and will be modulated by the two things that have always been concerns…early initiation and timing of trough ejection. And those finer details that will make or break this event cannot be resolved this far out with high confidence.

By all means stick to your guns.

I didn’t say there wouldn’t be any sort of severe weather or a bust. All I’m saying is that the comparisons to those infamous plains days are most likely misplaced and are upper echelon outbreaks for a reason.

Those were very rare events and I just don’t see Saturday coming close to those. You can still have a bad outbreak and not reach those aforementioned outbreak levels. Just my opinion, so do with it what you will.

 

[lake.effect]

It's worth mentioning that May 3rd 1999 started as a D1 Slight risk, the Moore 2013 EF5 was on a moderate risk day (and with a "low potential" of strong tornadoes per the SPC forecast), El Reno was a moderate day, etc...

Not drawing parallels between those events and Saturday, but it is interesting that the most historic (recent) tornado days in the plains were on Moderate days and nothing really stands out from the High Risk days.

 

[NorthGaWeather]

By all means stick to your guns.

I didn’t say there wouldn’t be any sort of severe weather or a bust. All I’m saying is that the comparisons to those infamous plains days are most likely misplaced and are upper echelon outbreaks for a reason.

Those were very rare events and I just don’t see Saturday coming close to those. You can still have a bad outbreak and not reach those aforementioned outbreak levels. Just my opinion, so do with it what you will.

Oh, I completely agree that the probability of seeing a 5/3/99 type event isn’t exceedingly high. I’ve never thought this would be a 70+ tornado event with EF-4/5s rampaging everywhere due to the potential limitations. To me, this has been a multiple tornadic supercell event with the potential for a couple of significant tornado families. That potential remains solid.

 

[Tempestas Tonitrua]

Oh, I completely agree that the probability of seeing a 5/3/99 type event isn’t exceedingly high. I’ve never thought this would be a 70+ tornado event with EF-4/5s rampaging everywhere due to the potential limitations. To me, this has been a multiple tornadic supercell event with the potential for a couple of significant tornado families. That potential remains solid.

Absolutely. Didn’t mean to misread your post and I hope I didn’t come across snarky in mine.

 

[jiharris0220]

Now of course, this event is still 2 days away and can still trend considerably in either direction.
Models could easily go back to showing a tornado apocalypse, or continue to go full 2024 and trend even further back to yet another run of the mil severe weather outbreak.
I think the main deciding factor is severity/extent of morning time convection. If there’s little and the warm sector is undisturbed, lapse rates will be allowed to deepen and really drive up streamwise vorticity in any updrafts that form.
Honestly the fact there’s even remotely any sort of confidence at this range is I dare say a relief?