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Chicago Storm

April 24-30th Severe Potential

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I disagree to an extent... It does not stunt the low-level circulation of the updraft that much, but the mid-level part of the updraft, yeah. We'll see, its been a little bit since we've had VBV problems with anything that had a higher-end chance. Something to watch is how much of a VBV we truly will have, I've seen some model runs that have showed VBV and some that show more uni-directional profiles above 700mb.

 

Ironically seven years ago to the date (4/26/09) was a high risk that busted due to VBV. I think that was that event that really shoved VBV into the spotlight as something that could deal-break a severe wx setup.

 

I've read some material that suggests the layer around 700mb, despite being up in the mid-levels, is critically important for storm mode and tornado development. But yeah, above 500mb VBV tends to be less of an issue (though not a non-issue). VBV can change quite drastically with even small changes in different layers, so yeah, I agree, we can't be 100% sure about its extent until it actually happens.

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Yes, storms developed pretty early on at 2:30ish in the afternoon (basically right when the H5 jet overspread the WS), and in about an hour or two numerous storms had developed and eventually congealed because they developed so closely together. But before the supercells clustered together, they were pretty potent given the environment that was in place that day. A few storms were able to stay discrete however. 

So the issue on 5/24 wasn't as much about VBV as it was about too many storms, right?

 

Interestingly, 5/24 had some SRH values pretty similar to what is forecast for this event. The big tornadoes of the day happened between 20-21z. Here's the 0-3km SRH per violent tornado archive for 21z

 

2hMTFAa.png

 

2011052418_full_oun_obssounding.gif

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Ironically seven years ago to the date (4/26/09) was a high risk that busted due to VBV. I think that was that event that really shoved VBV into the spotlight as something that could deal-break a severe wx setup.

 

Yes. Been thinking about that event a lot the past couple days. I wouldn't be surprised to see this heading for a similar outcome to that day or, at the very bottom end, 4/24/07. But at the same time, I wouldn't bank on it just yet. You never can bank on much of anything with these meridional, VBV setups until they're already underway.

 

The words from an SPC MD issued late afternoon on 4/26/09 still haunt me to this day: "CONFIDENCE IS HIGH IN A CLUSTER OF TORNADIC SUPERCELLS EVOLVING FROM WICHITA FALLS TO WOODWARD IN THE NEXT FEW HOURS." Kept reading it as we drove home on I-40 through stratiform rain during those few hours. This has to be the most nerve-wracking type of event for SPC and NWS WFOs. Amazing trough, amazing parameters, and messy storms that are only quasi-supercells... but one could separate or turn right 20 degrees and drop a sigtor at the drop of a hat. Even the Elmer day last year kind of falls into this category, too.

 

All that said, I'm increasingly interested in the far southern play in N TX. That mode was a colossal, epic fail on 26 April 2009, though, and it didn't look too dissimilar to this.

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Ironically seven years ago to the date (4/26/09) was a high risk that busted due to VBV. I think that was that event that really shoved VBV into the spotlight as something that could deal-break a severe wx setup.

 

I've read some material that suggests the layer around 700mb, despite being up in the mid-levels, is critically important for storm mode and tornado development. But yeah, above 500mb VBV tends to be less of an issue (though not a non-issue). VBV can change quite drastically with even small changes in different layers, so yeah, I agree, we can't be 100% sure about its extent until it actually happens.

That event also had a mini-mcs/ complex move across the high-risk area from about noon to nearly 2:30... So not sure that VBV was the only thing that went into play there. That was a messy day too since the shortwave ejected pretty dang early (obviously)  and triggered a lot of convection and there wasn't much cap/ EML in place... Something that has become a concern for tomorrow is that very same thing, about the shortwave ejecting a bit early, but really it depends which model you look at.

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I agree with you on the storm coverage.. it's not an overwhelming sign for discrete supercells. Too much coverage might turn out to be a problem - I really don't know at this point.

 

You mention 5/24/11... they lined out quickly because storm coverage rapidly increased and they eventually collided, no? I watched the SPC tornado forecast workshop last spring, and I recall Rich talked at least briefly about one of those violent tornadoes when on the topic of storm collisions. 

 

I have heard the same thing about 5/24/11, but I'm in the camp that believes that storm mergers are okay so long as you have the right shear profiles. The thing about 5/24/11, was that there was a relatively discrete supercell near Pauls Valley that simply evaporated after crossing I-35. Right before vanishing, the Pauls Valley supercell spit out a left-split that collided with the Goldsby supercell, which also vanished shortly thereafter. 

 

Contrast that with events like 5/23/08, which had many storm mergers as well, but ended up with a set of high-end tornadic supercells after dark.

 

My "guess" (for the lack of a better word that conveys the lack of scientific rigor here) is that there is some angular momentum transfer between colliding updrafts that can constructively or destructively interfere with each other. The presence of strong CCW streamwise vorticity allows the former to be favored over the latter; the presence of VBV causes the latter to be favored as it makes it that much more difficult for the original supercell to establish the rotation in its updraft.

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Yes. Been thinking about that event a lot the past couple days. I wouldn't be surprised to see this heading for a similar outcome to that day or, at the very bottom end, 4/24/07. But at the same time, I wouldn't bank on it just yet. You never can bank on much of anything with these meridional, VBV setups until they're already underway.

 

The words from an SPC MD issued late afternoon on 4/26/09 still haunt me to this day: "CONFIDENCE IS HIGH IN A CLUSTER OF TORNADIC SUPERCELLS EVOLVING FROM WICHITA FALLS TO WOODWARD IN THE NEXT FEW HOURS." Kept reading it as we drove home on I-40 through stratiform rain during those few hours. This has to be the most nerve-wracking type of event for SPC and NWS WFOs. Amazing trough, amazing parameters, and messy storms that are only quasi-supercells... but one could separate or turn right 20 degrees and drop a sigtor at the drop of a hat. Even the Elmer day last year kind of falls into this category, too.

 

All that said, I'm increasingly interested in the far southern play in N TX. That mode was a colossal, epic fail on 26 April 2009, though, and it didn't look too dissimilar to this.

That's brutal but I couldn't help but laugh at that misfortune. 

 

 

Good discussion. The best thing is that, with all this conceptual/hypothetical talk, we don't have to wait long now until this all starts to unfold. About 18 more hours. Even less than that until we can look at HRRR/RAP to get some answers to our questions with some reliability. I'd say 9-10 more hours for that(?)

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That's brutal but I couldn't help but laugh at that misfortune. 

 

 

Good discussion. The best thing is that, with all this conceptual/hypothetical talk, we don't have to wait long now until this all unfolds. About 18 more hours. Even less than that until we can look at HRRR/RAP to get some answers to our questions with some reliability.  

Literally... A week of hype and talk about this is all either going to come crashing down or materialize to be legitimate. It won't reach its original ceiling it had, but it still has the chance to be a big-day-- just is conditional. 

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Literally... A week of hype and talk about this is

Don't forget- Wednesday, Friday are already slight (or 15%) risk (as per the SPC) and Thursday and Saturday might get a slight risk. There will probably be a few more tornadoes in various places on these days.

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The one place you've really got to be pulling for to be spared is Andover, KS. Tomorrow is the 25th anniversary of that ridiculous motion in the funnel F5.

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I can't help but chuckle at all the 'hypecasters' suddenly crapping on tomorrow like its a bad batch of guacamole. Yet another example of why folks should keep their enthusiasm under control when looking at a potential event over 3 days out. I expect we'll have some weak-end tornadoes in North Texas into Oklahoma tomorrow but it would take a mesoscale accident for anything more. The biggest issue will be monster hail. I wouldn't be too surprised to see a small 60% hatched hail at some point tomorrow. (I haven't looked north of I-40 so my thoughts don't include KS/NE). 

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NSSL WRF (which, in my experience, is the most reliable of the many convection-allowing models run at 00z) is quite discouraging for most of the dryline. Plenty of storms, and many are even discrete with space, but little UH to speak of. A reflection of the abysmal hodographs. It suggests a northern (N KS) and southern (TX) mode to any serious threat, which seems increasingly plausible.

 

At least it doesn't develop any early-day convection, though.

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NSSL WRF (which, in my experience, is the most reliable of the many convection-allowing models run at 00z) is quite discouraging for most of the dryline. Plenty of storms, and many are even discrete with space, but little UH to speak of. A reflection of the abysmal hodographs. It suggests a northern (N KS) and southern (TX) mode to any serious threat, which seems increasingly plausible.

 

At least it doesn't develop any early-day convection, though.

WRF-NMMB and WRF-ARW are pretty similar too, with the WRF-NMMB maybe being a little better. 

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NSSL WRF (which, in my experience, is the most reliable of the many convection-allowing models run at 00z) is quite discouraging for most of the dryline. Plenty of storms, and many are even discrete with space, but little UH to speak of. A reflection of the abysmal hodographs. It suggests a northern (N KS) and southern (TX) mode to any serious threat, which seems increasingly plausible.

 

At least it doesn't develop any early-day convection, though.

 

Unlike WRF ARW and NMMB. Ew.

 

HRRRX is more encouraging for the dryline in OK

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NSSL WRF (which, in my experience, is the most reliable of the many convection-allowing models run at 00z) is quite discouraging for most of the dryline. Plenty of storms, and many are even discrete with space, but little UH to speak of. A reflection of the abysmal hodographs. It suggests a northern (N KS) and southern (TX) mode to any serious threat, which seems increasingly plausible.

 

At least it doesn't develop any early-day convection, though.

are you talking about the --NCEP 4.0 km WRF-NMM run for SPC -- model or a different one? Because that one has convection in central OK early in the day, 15-16z, and plenty of convection near the warm front, before sunrise. Looks like a total mess.

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are you talking about the --NCEP 4.0 km WRF-NMM run for SPC -- model or a different one? Because that one has convection in central OK early in the day, 15-16z, and plenty of convection near the warm front, before sunrise. Looks like a total mess.

 

Nope, that's yet another 4 km WRF variant. :lol:

 

We have the NSSL WRF available on Pivotal Weather now, and it's also available directly from NSSL.

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Nope, that's yet another 4 km WRF variant. :lol:

 

We have the NSSL WRF available on Pivotal Weather now, and it's also available directly from NSSL.

I just was checking that. after I realized you must not have been talking about the "4.0km run for SPC". Oddly, if you look at hour 23, (on the NSSL) the thunderstorms have a pattern shaped like a big "?" in Kansas. I could only imagine that plenty of forecasters and storm chasers have question marks in their minds.

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First time playing with the NSSL-WRF, what's with the abysmal STP on there during showtime?

it has a boat load of convection across much of the warm sector.

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SPC outlook is roughly what I expected. 10% tornado probs w/ sig hatch, and 45% for hail, 30% for dmgg wind. Mention of the complicated scenario, some possibility for strong tornadoes, and large hail being the main threat.

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Dry adiabatic lapse rates on the 00z ABQ sounding (even superadiabatic down low). Needless to say, I think there's going to be a lot of hail damage tomorrow when this EML advects out eastward. This time of year, you're likely not going to see a much more explosive thermodynamic environment than will exist tomorrow.

 

ABQ.gif

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Dry adiabatic lapse rates on the 00z ABQ sounding (even superadiabatic down low). Needless to say, I think there's going to be a lot of hail damage tomorrow when this EML advects out eastward. This time of year, you're likely not going to see a much more explosive thermodynamic environment than will exist tomorrow.

 

ABQ.gif

So vastly different from last year's situation. Looking forward to the summer severe season.

 

I'm surprised SPC didn't go 60% hail. If there was a setup that warranted 60% hail, this would be it.

Probably later

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For those who are awake this late at night, the HRRRX 04z run is mostly completed, available at Weatherbell (for free). I honestly have no idea if this will run at 05z or any other time of the day.

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If you loop the IR centered over TX and over NM, you can see there is a bit of a gravity wave moving through. Here is an image from about 90 minutes ago:

 

0jErAhp.gif

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Looks like there is already tennis ball sized hail this morning over northeast Kansas. Going to be some massive hail later today when everything else comes together.

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It will be interesting to see to what extent the morning complex of storms plays into the overall setup this afternoon. Noticed an outflow boundary being kicked out across the I-70 corridor now and moving southwest. 

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If you loop the IR centered over TX and over NM, you can see there is a bit of a gravity wave moving through. Here is an image from about 90 minutes ago:

 

0jErAhp.gif

That could make things interesting...

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