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Chicago Storm

April 24-30th Severe Potential

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Y'all are talking about SRH being an issue... I agree. But if there's any supercells remaining after ~00z, the nocturnal LLJ should kick in and increase the SRH as CAPE decreases. The way I see it is the supercells will start out with a threat for giant hail, but the tornado threat increases as the sun sets and the nocturnal LLJ kicks in and elongates the hodograph. The significant tornado threat persists until everything grows into a line.

 

2 caveats that throws a wrench into the whole "plan" is 

1) Supercells become elevated quickly after sunset (don't know if that's gonna happen; I don't think so)

2) If the storms form a line quicker than ICT's thinking of after 03z.

 

That's my novice thinking. I think the potential for high risk is there in that window between the nocturnal LLJ and the evolution of the squall... but it'll have to wait until specifics become clear. If they become clear.

 

Ariel Cohen PhD and Rich Thompson (SPC mesoscale assistant/fire weather forecaster and lead forecaster, respectively) disagree considering how things stand as of now (though in all fairness, it could change).

https://twitter.com/akracki

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The graphics coming out of KFOR never fail to piss me off. So unbelievably stupid and and do nothing but scare their viewing area. It's one thing to get people prepared, it's something entirely different to act like you can predict the EF rating of a tornado before it occurs. The people of Oklahoma do not need these dopey graphics to know tornadoes are dangerous.

Let me hop off my soap box now.

 

 

 

Same guy who also did this.

 

 

 

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Not sure if Mike Morgan is just always overly optimistic, stupid, or both. Needs to stop with the incessant use of the EF scale on air and on graphics.

It doesn't even say EF. Just F.

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IF something like the 00Z HRRR/RAP occurred and we get some morning convection ( as long as it does not linger, and last well into the afternoon or leave a ton of cloud debris behind, which I doubt that it would due to the incoming EML), it could actually help for later on in the day. By providing a vorticity rich environment as well as OFBs to provide some significant local enhancement of SRH. Counting on that initiation were to reoccur at a favorable time later on in the day, and that convection did not just constantly continue to pop up.

 

On another note, it looks like the convection that will occur tonight over NE KS/ WC MO will drop an OFB somewhere across EC KS, I believe. 

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00Z RAP looking as though things could pop pretty early. Already has the jetcore overspreading the warm sector at 15Z in OK.

As expected.

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IF something like the 00Z HRRR/RAP occurred and we get some morning convection ( as long as it does not linger, and last well into the afternoon or leave a ton of cloud debris behind, which I doubt that it would due to the incoming EML), it could actually help for later on in the day. By providing a vorticity rich environment as well as OFBs to provide some significant local enhancement of SRH. Counting on that initiation were to reoccur at a favorable time later on in the day, and that convection did not just constantly continue to pop up.

 

On another note, it looks like the convection that will occur tonight over NE KS/ WC MO will drop an OFB somewhere across EC KS, I believe. 

 

Similar progression happened during May 24th, just further west

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So this is quite a change at 00Z in C OK on the 4K NAM... No convection near any of the best parameters on the 4NAM in C OK, despite being completely uncapped, so find it hard to believe.

post-7962-0-71125800-1461637235_thumb.pn

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Ariel Cohen PhD and Rich Thompson (SPC mesoscale assistant/fire weather forecaster and lead forecaster, respectively) disagree considering how things stand as of now (though in all fairness, it could change).

https://twitter.com/akracki

I'm aware. They've probably been doing this kind of thing longer than I've been alive, so I value their opinion more than mine. But 24 hours from now, I want to see how wrong I am. It's a learning thing.

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Y'all are talking about SRH being an issue... I agree. But if there's any supercells remaining after ~00z, the nocturnal LLJ should kick in and increase the SRH as CAPE decreases. The way I see it is the supercells will start out with a threat for giant hail, but the tornado threat increases as the sun sets and the nocturnal LLJ kicks in and elongates the hodograph. The significant tornado threat persists until everything grows into a line.

 

2 caveats that throws a wrench into the whole "plan" is 

1) Supercells become elevated quickly after sunset (don't know if that's gonna happen; I don't think so)

2) If the storms form a line quicker than ICT's thinking of after 03z.

 

That's my novice thinking. I think the potential for high risk is there in that window between the nocturnal LLJ and the evolution of the squall... but it'll have to wait until specifics become clear. If they become clear.

 

 
It and HRRR don't seem to be handling the very near-term very well.
 
At all.

 

I see two opps for tors, initial development for cells, once they reach initial maturity, then could produce smaller spin ups off/on as the updrafts reorganize as they do in low shear environments...hail is a mammoth threat.  

Agree that if cells stay discreet the threat goes up from 8pm - 11pm or so...NAM blows up convection early afternoon and through Tulsa by about 7pm...not sure about that...

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Both the NAM and 4K NAM are showing improvement in the LLVL winds and corresponding SRH so lets see what the other hi-res guidance does tonight with that... as well as the GFS/ECMWF. Also, lets see what they all do with the potential effects of early initiation as well. Not sure I believe the NAM's precip depiction... seems odd.

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Instead of bashing on a certain TV station, what are some good stations that might have streaming coverage? Channel 9 OKC? KAKE-Wichita?

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Instead of bashing on a certain TV station, what are some good stations that might have streaming coverage? Channel 9 OKC? KAKE-Wichita?

KFOR does usually provide pretty good coverage too-- despite the occasional hyperbole. 

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Y'all are talking about SRH being an issue... I agree. But if there's any supercells remaining after ~00z, the nocturnal LLJ should kick in and increase the SRH as CAPE decreases. The way I see it is the supercells will start out with a threat for giant hail, but the tornado threat increases as the sun sets and the nocturnal LLJ kicks in and elongates the hodograph. The significant tornado threat persists until everything grows into a line.

 

2 caveats that throws a wrench into the whole "plan" is 

1) Supercells become elevated quickly after sunset (don't know if that's gonna happen; I don't think so)

2) If the storms form a line quicker than ICT's thinking of after 03z.

 

That's my novice thinking. I think the potential for high risk is there in that window between the nocturnal LLJ and the evolution of the squall... but it'll have to wait until specifics become clear. If they become clear.

 

 
It and HRRR don't seem to be handling the very near-term very well.
 
At all.

 

 

So here's the thing, this is how I see it... weak SRH isn't the problem... it's a symptom of the problem. When storms form tomorrow, without the proper shear profiles, they are going to congeal into a complete mess. Form into lines, clusters, etc. Interfering with each other. Very quickly. There's a small window before this happens for a tor to drop, but given the strong forcing for ascent from the negatively tilted trough, and the potential energy available for updraft growth, I'm not holding my breath for storms to remain isolated.

 

SRH is a measure of the spin that's available for updrafts to ingest and focus. If the updrafts are wacked up due to VBV, or storm interference, all the spin in the world doesn't matter, because the updrafts simply can't utilize it. 

 

There's multiple ways that you can overcome crappy SRH (boost the streamwise vorticity around a boundary, nocturnal LLJ intensification, etc.), but it's a lot more difficult to get around crappy storm mode. SRH isn't enough to tell you when storms will or will not tend to merge into clusters. You need to actually look at the whole hodograph and wind profiles for that, and that isn't pretty for tomorrow.

 

P.S. this wasn't meant to be directed at you solely, more of PSA to everyone...

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Instead of bashing on a certain TV station, what are some good stations that might have streaming coverage? Channel 9 OKC? KAKE-Wichita?

KWTV/News 9 in OKC does a good job. They're bringing in two helicopters tomorrow so you might get some nice shots. 

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KFOR does usually provide pretty good coverage too-- despite the occasional hyperbole. 

 

Mike Morgan is unlistenable.

 

KWTV is ok and David has generally toned things down since becoming the lead. KAKE and KSN for Wichita.

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to my friends between Waco and San Antonio and College Station, any plans for someone maybe sending up a special sounding for the upcoming 12Z and 00Z timeframes down that way to asses the potential capping down there? especially say Ft. Hood, Austin, New Braunfels, College Station? 

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So here's the thing, this is how I see it... weak SRH isn't the problem... it's a symptom of the problem. When storms form tomorrow, without the proper shear profiles, they are going to congeal into a complete mess. Form into lines, clusters, etc. Interfering with each other. Very quickly. There's a small window before this happens for a tor to drop, but given the strong forcing for ascent from the negatively tilted trough, and the potential energy available for updraft growth, I'm not holding my breath for storms to remain isolated.

 

SRH is a measure of the spin that's available for updrafts to ingest and focus. If the updrafts are wacked up due to VBV, or storm interference, all the spin in the world doesn't matter, because the updrafts simply can't utilize it. 

 

There's multiple ways that you can overcome crappy SRH (boost the streamwise vorticity around a boundary, nocturnal LLJ intensification, etc.), but it's a lot more difficult to get around crappy storm mode. SRH isn't enough to tell you when storms will or will not tend to merge into clusters. You need to actually look at the whole hodograph and wind profiles for that, and that isn't pretty for tomorrow.

 

P.S. this wasn't meant to be directed at you solely, more of PSA to everyone...

I do not think VBV is as damning to supercells as you make it sound. You certainly can still have tornadic supercells in an environment that has a VBV signature, just look at 5/24/11 IIRC that had some VBV issues, while, yes, the wind fields that day were a deal stronger, still shows that you can get plenty of supercells with VBV problems. If anything for tomorrow it might just make the supercells that WILL form at some point tomorrow a bit more HP than preferable. Now whether we get more clusters than supercells remains to be seen. If anything remains discrete/semi-discrete into the 00z-04z time frame, things could get pretty interesting given the increase in helicities--possibly to 300m2/s2 at both 0-1KM and 0-3KM eventually-- due to the strengthening LLJ. Even if there is predominately more clusters tomorrow than discrete/semi-discrete supercells, the tornado threat will still increase in this time frame. In any case, you are right that we will see a mixed-storm mode, not everything is going to be clusters, and not everything is going to be a discrete supercell. Probably a decent amount of storm interactions too... No matter the storm mode though, these things are going to produce monster hail, and that in itself is a significant hazard.

 

I am not saying we really have a high-end tornado threat by any means--because we really do not anymore. But just saying that I wouldn't be so adamant about VBV entirely ruining the tornado threat. A tornado threat is still evident. 

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Guys, Mike Morgan is more nutty than a squirrel's drey. We don't need his nonsense cluttering the thread.

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5/24/11 had some degree of VBV issues, sure, but I don't recall the forecast hodos being nearly as ugly as what the 00z NAM is painting. The lowest 3 km AGL were huge and textbook shape, and it was more just a matter of some weirdness above H5. I only wish that was the only concern tomorrow. These remind me more of something like 26 April 2009 or 17 April 2013.

 

Although I can generally agree with your assessment of the situation after re-reading it, jojo.

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So here's the thing, this is how I see it... weak SRH isn't the problem... it's a symptom of the problem. When storms form tomorrow, without the proper shear profiles, they are going to congeal into a complete mess. Form into lines, clusters, etc. Interfering with each other. Very quickly. There's a small window before this happens for a tor to drop, but given the strong forcing for ascent from the negatively tilted trough, and the potential energy available for updraft growth, I'm not holding my breath for storms to remain isolated.

 

SRH is a measure of the spin that's available for updrafts to ingest and focus. If the updrafts are wacked up due to VBV, or storm interference, all the spin in the world doesn't matter, because the updrafts simply can't utilize it. 

 

There's multiple ways that you can overcome crappy SRH (boost the streamwise vorticity around a boundary, nocturnal LLJ intensification, etc.), but it's a lot more difficult to get around crappy storm mode. SRH isn't enough to tell you when storms will or will not tend to merge into clusters. You need to actually look at the whole hodograph and wind profiles for that, and that isn't pretty for tomorrow.

 

P.S. this wasn't meant to be directed at you solely, more of PSA to everyone...

I thought SRH had more to do with tornadoes than just having a supercell. In my meager ~2 years experience in this, I've seen plenty of supercells... mostly in the Plains... that existed with negligible 0-3km SRH, but were no doubt a supercell. There was low-level veering, but almost no low-level winds.

 

You mention storm interference... but that's also gotta depend on how many storms initiate tomorrow. If we get a discrete supercell, there's not gonna be anything for it to interfere with. From the way you worded your post, I get the impression of a typical OV multicell damaging wind severe "event" where an elongated squall line forms in 30 minutes... not an initial dryline event where there's 4000 j/kg CAPE, 50-60 knots 0-6km shear, and 150-200 m2/s2 0-3km SRH. That's not to say I don't believe this whole VBV thing... because it makes conceptual sense to me... but as frustrating as it would be for chasers, I'd kinda like to see a discrete supercell just fall apart in the environment tomorrow without interfering with any other storms. I just can't imagine that happening. 

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I do not think VBV is as damning to supercells as you make it sound. You certainly can still have tornadic supercells in an environment that has a VBV signature, just look at 5/24/11 IIRC that had some VBV issues, while, yes, the wind fields that day were a deal stronger, still shows that you can get plenty of supercells with VBV problems. If anything for tomorrow it might just make the supercells that WILL form at some point tomorrow a bit more HP than preferable. Now whether we get more clusters than supercells remains to be seen. If anything remains discrete/semi-discrete into the 00z-04z time frame, things could get pretty interesting given the increase in helicities--possibly to 300m2/s2 at both 0-1KM and 0-3KM eventually-- due to the strengthening LLJ. Even if there is predominately more clusters tomorrow than discrete/semi-discrete supercells, the tornado threat will still increase in this time frame. In any case, you are right that we will see a mixed-storm mode, not everything is going to be clusters, and not everything is going to be a discrete supercell. Probably a decent amount of storm interactions too... No matter the storm mode though, these things are going to produce monster hail, and that in itself is a significant hazard.

 

I am not saying we really have a high-end tornado threat by any means--because we really do not anymore. But just saying that I wouldn't be so adamant about VBV entirely ruining the tornado threat. A tornado threat is still evident. 

 

Yes, 5/24/11 had some VBV issues. And after the initial violent tornadoes, everything lined out very quickly. If I recall correctly, that's precisely when the wind profiles started getting messy.

 

VBV isn't HP supercells -- that's more of a function of hodograph length and deep-layer shear than anything. Recall that the positive area between the hodograph and the storm motion vector (helicity) is CCW (+) streamwise vorticity. Which ascending parcels will ingest. Adding in a VBV effectively superimposes an opposing CW (-) vorticity on top of that CCW vorticity in the VBV layer. I don't know the exact physical dynamics, but for an updraft that is rotating CCW, adding in that CW vorticity component stunts its growth.

 

Just from my experience, but storms that form in a VBV aren't just HP -- they look very "off". Maybe I did oversell the VBV a little, and yes tomorrow still has high-end hail potential and definitely nonzero tornado potential, but VBV is a serious issue for storms.

 

All that said, the 0Z NAM seemed to hold back on the VBV a little, so we shall see.

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I thought SRH had more to do with tornadoes than just having a supercell. In my meager ~2 years experience in this, I've seen plenty of supercells... mostly in the Plains... that existed with negligible 0-3km SRH, but were no doubt a supercell. There was low-level veering, but almost no low-level winds.

 

You mention storm interference... but that's also gotta depend on how many storms initiate tomorrow. If we get a discrete supercell, there's not gonna be anything for it to interfere with. From the way you worded your post, I get the impression of a typical OV multicell damaging wind severe "event" where an elongated squall line forms in 30 minutes... not an initial dryline event where there's 4000 j/kg CAPE, 50-60 knots 0-6km shear, and 150-200 m2/s2 0-3km SRH. That's not to say I don't believe this whole VBV thing... because it makes conceptual sense to me... but as frustrating as it would be for chasers, I'd kinda like to see a discrete supercell just fall apart in the environment tomorrow without interfering with any other storms. I just can't imagine that happening. 

 

Yeah, that's correct, a solid supercell can form with little helicity but good updraft/downdraft separation, which tend to depend on deep-layer shear more.

 

I'm going to have to go with the over on the number of storms initiating tomorrow. You have a negatively-tilted trough and arrival of large-scale ascent timed well with peak heating, impinging on a ridiculously unstable, buoyant warm sector. Also the NAM just joined in the set of models that are convecting pretty early, at or before 21Z.

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Just curious and posted on Texas thread to not clutter this one with nonsense, but it's the first I saw it pop up on the COD site sounding for the metroplex for this storm. The 03z NAM sounding generated a potential hazard type of PDS Tornado. Is this area a bigger concern than thought or just model fluff?

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Yes, 5/24/11 had some VBV issues. And after the initial violent tornadoes, everything lined out very quickly. If I recall correctly, that's precisely when the wind profiles started getting messy.

 

VBV isn't HP supercells -- that's more of a function of hodograph length and deep-layer shear than anything. Recall that the positive area between the hodograph and the storm motion vector (helicity) is CCW (+) streamwise vorticity. Which ascending parcels will ingest. Adding in a VBV effectively superimposes an opposing CW (-) vorticity on top of that CCW vorticity in the VBV layer. I don't know the exact physical dynamics, but for an updraft that is rotating CCW, adding in that CW vorticity component stunts its growth.

 

Just from my experience, but storms that form in a VBV aren't just HP -- they look very "off". Maybe I did oversell the VBV a little, and yes tomorrow still has high-end hail potential and definitely nonzero tornado potential, but VBV is a serious issue for storms.

 

All that said, the 0Z NAM seemed to hold back on the VBV a little, so we shall see.

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.

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Yeah, that's correct, a solid supercell can form with little helicity but good updraft/downdraft separation, which tend to depend on deep-layer shear more.

 

I'm going to have to go with the over on the number of storms initiating tomorrow. You have a negatively-tilted trough and arrival of large-scale ascent timed well with peak heating, impinging on a ridiculously unstable, buoyant warm sector. Also the NAM just joined in the set of models that are convecting pretty early, at or before 21Z.

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. 

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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.

So jojo am I going to get Pwned into oblivion tomorrow night??

Sent from my HTC6525LVW using Tapatalk

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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. 

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. 

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