Severe weather risk 4/30 - 5/3

[Quincy]

18 minutes ago, jojo762 said:

Fairly uneventful day. Tomorrow could be better in KS/MO.

This one honestly performed below my expectation, but the writing was on the wall, again. The special NSSL sounding out of Elk City threw up a flag, even if it was subtle. It showed a modest veer-back-veer signature. This was also noted, to some degree, in the 21z OUN sounding. It could have been overcome, if low-level shear was stronger, and storms remained more widely spaced. Storms went up quick and there was a bunch of congestion in western Oklahoma. It should be little surprise given the amount of instability and upper level forcing. 

[SmokeEater]

Circulation over Purcell about to go TW'd.

Sent from my SM-G950U using Tapatalk

[DanLarsen34]

2 minutes ago, Quincy said:

This one honestly performed below my expectation, but the writing was on the wall, again. The special NSSL sounding out of Elk City threw up a flag, even if it was subtle. It showed a modest veer-back-veer signature. This was also noted, to some degree, in the 21z OUN sounding. It could have been overcome, if low-level shear was stronger, and storms remained more widely spaced. Storms went up quick and there was a bunch of congestion in western Oklahoma. It should be little surprise given the amount of instability and upper level forcing. 

Same old story for Plains tornado days the past couple of years. Any red flag in a set up seems to come to fruition in significantly mitigating an otherwise dangerous environment.

[Drz1111]

What is the scientific evidence that VBV is bad for tornados, other than that it generally coincides with upper flow that’s parallel to a boundary?

[Quincy]

5 minutes ago, Drz1111 said:

What is the scientific evidence that VBV is bad for tornados, other than that it generally coincides with upper flow that’s parallel to a boundary?

There are mixed thoughts on this. If the VBV signature is subtle enough, then it may not have much impact. However, if winds suddenly/sharply change direction with height, you'll see jagged hodographs. If the VBV is elevated enough, it won't have much impact on low level helicity. I would tend to think that VBV signatures can lead to less-than-optimal shear for sustained, robust, long-lived supercells. What we saw today were some supercells, albeit closely clustered, that didn't really have much strong rotation. This is evident in the lack of very large hail, which is why SPC upgraded northwestern Oklahoma to moderate risk... Any tornadoes were very brief and that includes before the QLCS formed. 

I can't put a finger on one key factor that limited the tornado threat. I don't think VBV played a big role, but it was part of multiple issues, including modest low-level shear, early initiation and cell interaction. 

Upon closer examination of the NSSL sounding, the VBV signature was more detrimental to intense supercell development, given its presence in the mid-levels. Most of the 0-3km SRH was located in the 0-1km layer, which is what you do want to see when it comes to tornado potential.

Just another weird, but largely underperforming setup in the Plains.

[andyhb]

I'm gonna bet tomorrow is going to yield more tornadoes than today assuming all of the current convection isn't overly detrimental.

[Buckeye05]

Two likely QLCS tornadoes just moved through the KC area.

[yoda]

6 minutes ago, Buckeye05 said:

Two likely QLCS tornadoes just moved through the KC area.

Severe weather statements at 925pm saying weather spotters confirmed tornadoes with the warnings in KC

[Buckeye05]

Another one near Ralston, OK.

[Radtechwxman]

19 minutes ago, andyhb said:

I'm gonna bet tomorrow is going to yield more tornadoes than today assuming all of the current convection isn't overly detrimental.

Kind of my gut feeling to. Looking at upper air data it doesn't look like the jet hardly ejected out to me. Am I wrong? Also I don't recall VBV even being shown in models or forecasted. So weird

[Chinook]

I have heard a preliminary report that there was a tornado near Amber, OK. Source: https://twitter.com/tornadoslayer_

[Quincy]

Storms are still ongoing, but I think tomorrow's worth a peek.

The setup is complex and there isn't much more clarity than there was before, but I can highlight some threat zones as I see them...

Eastern Kansas has the best model support. Multiple boundaries should come into play and we may have both a dryline and cold front to work with, as well as anything leftover from overnight/early day convection. Shear profiles have improved from previous model runs, although like today, the wind fields don't look perfect. Notice how the hodographs tend to be a bit elongated and jagged in parts of eastern Kansas tomorrow afternoon. Yes, shear. Deep layer shear vectors, based on the HRRR, look about perpendicular to the dryline. 850/500 crossovers also show decent veering with height. Convection allowing models (CAMs) show multiple discrete/semi-discrete cells forming by early to mid afternoon, likely do to strong boundary layer heating and minimal capping. The caveat might be a tendency for cell interaction to preclude a more impressive severe outbreak, but we'll see.

Northern Missouri (possibly southern Iowa) is another decent target. Even with early day convection, most CAMs show strong heating in place by midday. Low-level wind fields are very good, with SSE to SE near-surface winds a good bet. The most probable scenario would feature sporadic supercells, potentially focusing along remnant outflow. If anyone is out chasing, be prepared to change course, especially if early day convection is more widespread than expected.

I have less confidence in robust convection in Illinois, but it's still possible on a localized level. Morning convection is progged in virtually every CAM and with limited boundary layer heating, I am not too impressed with the overall environment.

Yet another area would be the eastern half of Oklahoma into northeastern Texas. Down here, weaker large scale forcing and stronger capping will probably result in only isolated convection. Should any sustained updrafts form, expect them to take advantage of large buoyancy and favorable shear to produce severe storms. For anyone chasing, terrain and road networks are not ideal in this area, but if you're a local, it might be a good play that does not risk wasting too much time/driving.

@StormChaser4Life I hope I wasn't overplaying the role of VBV today. With that said, the models did show some subtle VBV signatures this morning. I touched on it in my blog, although I didn't think it was going to be much of a factor.

[Chinook]

Jeff Piotrowski posted a pic of a tornado at Chattanooga, OK

https://twitter.com/Jeff_Piotrowski

[Radtechwxman]

9 minutes ago, Quincy said:

Storms are still ongoing, but I think tomorrow's worth a peek.

The setup is complex and there isn't much more clarity than there was before, but I can highlight some threat zones as I see them...

Eastern Kansas has the best model support. Multiple boundaries should come into play and we may have both a dryline and cold front to work with, as well as anything leftover from overnight/early day convection. Shear profiles have improved from previous model runs, although like today, the wind fields don't look perfect. Notice how the hodographs tend to be a bit elongated and jagged in parts of eastern Kansas tomorrow afternoon. Yes, shear. Deep layer shear vectors, based on the HRRR, look about perpendicular to the dryline. 850/500 crossovers also show decent veering with height. Convection allowing models (CAMs) show multiple discrete/semi-discrete cells forming by early to mid afternoon, likely do to strong boundary layer heating and minimal capping. The caveat might be a tendency for cell interaction to preclude a more impressive severe outbreak, but we'll see.

Northern Missouri (possibly southern Iowa) is another decent target. Even with early day convection, most CAMs show strong heating in place by midday. Low-level wind fields are very good, with SSE to SE near-surface winds a good bet. The most probable scenario would feature sporadic supercells, potentially focusing along remnant outflow. If anyone is out chasing, be prepared to change course, especially if early day convection is more widespread than expected.

I have less confidence in robust convection in Illinois, but it's still possible on a localized level. Morning convection is progged in virtually every CAM and with limited boundary layer heating, I am not too impressed with the overall environment.

Yet another area would be the eastern half of Oklahoma into northeastern Texas. Down here, weaker large scale forcing and stronger capping will probably result in only isolated convection. Should any sustained updrafts form, expect them to take advantage of large buoyancy and favorable shear to produce severe storms. For anyone chasing, terrain and road networks are not ideal in this area, but if you're a local, it might be a good play that does not risk wasting too much time/driving.

@StormChaser4Life I hope I wasn't overplaying the role of VBV today. With that said, the models did show some subtle VBV signatures this morning. I touched on it in my blog, although I didn't think it was going to be much of a factor.

Great synopsis. Seems like a lot of the energy held back which was a fear all week. What happened to progressive low amplitude troughs taking on a nice neg tilt?!

[bdgwx]

HRRRX lights up the warm sector like a Christmas tree tomorrow. Lots of big boy UH tracks along the entire MO/IA border with plenty of activity to spare in central MO as well. The GFS really likes the idea of a prolific break out of activity in MO. 21Z SREF was modestly bullish for tornado ingredients in northern MO. There's still a lot of mitigating factors, but I agree that tomorrow may have more potential than today.

[Quincy]

4 minutes ago, bdgwx said:

HRRRX lights up the warm sector like a Christmas tree tomorrow. Lots of big boy UH tracks along the entire border MO/IA border with plenty of activity to spare in central MO as well. The GFS really likes the idea of a prolific break out of activity in MO. 21Z SREF was modestly bullish for tornado ingredients in northern MO. There's still a lot of mitigating factors, but I agree that tomorrow may have more potential than today.

The new HREF goes nuts up there too (IA/MO border region). 

Biggest kicker (pun intended) may be the upper level jet punching into the lower Missouri Valley late tomorrow. 

[jojo762]

Much like Quincy and others I'm a bit perplexed as to what exactly made today fail the relatively achievable expectations I had for it. For yet ANOTHER previously hyped up plains tornado day (since every single one of these type of days has always been hyped up days 6 through 4, only to fall apart come <72 hours) we had discrete/semi-discrete supercells during prime-time that failed to produce anything that wasn't insignificant/brief. Perhaps it was the VBV, but I'm not sure... truly perplexing. 

The last few years have been remarkably frustrating. 

[Torchageddon]

On 5/1/2018 at 5:12 PM, weatherextreme said:

Twitch is a great platform to use. I'm surprised that there are not more chasers who use it. 

I had to look up if Twitch allows non-gaming streams now and they do...sounds like they are going back to what they were before (Justin) which is not surprising at all.

As the main convective zones are linear now, there is the exception of south central Texas where supercells are mostly maintaining themselves. Pretty healthy ones. Not long ago the most southern one had a tornado warning on it. I keep seeing this even on non-prominent days later in the season. There usually is some monster supercell lurking down there isolated. Topography/micro-climate influence?

[Jonbo]

Targeted the Bedford area (away from convergence mania until I'm experienced) which was promising but like others said, lined out too quickly. Managed to be on the storm that went tor warned in SW Iowa. Had a really great base but it didn't materialize any further. 

[Chicago Storm]

This one honestly performed below my expectation, but the writing was on the wall, again. The special NSSL sounding out of Elk City threw up a flag, even if it was subtle. It showed a modest veer-back-veer signature. This was also noted, to some degree, in the 21z OUN sounding. It could have been overcome, if low-level shear was stronger, and storms remained more widely spaced. Storms went up quick and there was a bunch of congestion in western Oklahoma. It should be little surprise given the amount of instability and upper level forcing. 

On top of that, the 21z OUN sounding still showed a stout cap and high LFC.




.

[Jebman]

2 hours ago, Torchageddon said:

I had to look up if Twitch allows non-gaming streams now and they do...sounds like they are going back to what they were before (Justin) which is not surprising at all.

As the main convective zones are linear now, there is the exception of south central Texas where supercells are mostly maintaining themselves. Pretty healthy ones. Not long ago the most southern one had a tornado warning on it. I keep seeing this even on non-prominent days later in the season. There usually is some monster supercell lurking down there isolated. Topography/micro-climate influence?

I hope not, I have relatives in Austin, Buda, New Braunfels, near Dallas and in various other parts of South Central Texas.

[nwohweather]

Would bet that the cell west of Fort Worth has a tornado on it right now. Would have an absolute violent twister if there was no CIN at the surface, the instability and helicity are through the rough around it at the moment with no storms around it to really bother

[Quincy]

Looks like today is going to find a way to underperform too. While some severe is still possible up in the lower Missouri Valley, recent trends suggest convection over OK/MO is going to be detrimental to the eastern portion of the risk zone. That large 5-10% TOR area in the latest day 1 outlook is probably going to need to be scaled back. I wonder what else could go wrong. 

[Sydney Claridge]

Severe thunderstorm watch across much of central and north-central Texas, but I'm starting to wonder about tornado potential as the forecast effective helicity over the next 6 hours or so (per SPC mesoanalysis page) seems to be high in central TX, SE OK, and W AR with a broad forecasted area of 300+ (m2/s2) ESRH.  Though helicity and the like tends to be higher in the overnight and early morning anyways, some of this forecast helicity is into the early afternoon.  I'm personally wondering if this could mean anything with respect to tornado potential?  That said, everything seems relatively linear so far, so perhaps some QLCS spinups are the most likely scenario?

 

[the ghost of leroy]

9 hours ago, jojo762 said:

Much like Quincy and others I'm a bit perplexed as to what exactly made today fail the relatively achievable expectations I had for it. For yet ANOTHER previously hyped up plains tornado day (since every single one of these type of days has always been hyped up days 6 through 4, only to fall apart come <72 hours) we had discrete/semi-discrete supercells during prime-time that failed to produce anything that wasn't insignificant/brief. Perhaps it was the VBV, but I'm not sure... truly perplexing. 

The last few years have been remarkably frustrating. 

then don't hype it.  you're one of the guys here who most consistently gets a boner over forecasted events, putting out these massive posts listing off every parameter. lots of people were urging caution all along, or at least tempering their optimism.

[nrgjeff]

Greater KCMO area dews have been scoured by that MCS. Still low 60s Td but need upper 60s. LLJ is coming off ongoing convection; so, it will be impotent. Best chance for a spinner is a miracle up on the WF Missouri-Iowa border. It is decent terrain in contrast to much of Missouri, but the actual storms are subject to visibility challenges ongoing this week.

Other choices include chasing the DFW Metroplex, nah, and jungles east of the rest of the squall line, heck no!

The main problem yesterday was low level wind direction. VBV was in a tough spot; above 700 mb would have been easier to overcome. However, even with that crap, more backed surface to 925 mb winds would have done the trick. Just did not quite come together even with the LLJ. Hype accusations are not fair. Synoptic pattern was textbook. Come game day though, it's all about the meso-scale.

My secondary problem yesterday was boundaries did not work out. The US-160 boundary simply did not work. Felt like watching a basketball player go ice cold laying bricks. I'm shocked the OFB/DL bulge failed in OK. That's rolling your ankle in the game, lol. Both likely suffered from the not-backed low level winds. Glad it was just a virtual chase!

[Chicago Storm]

Today is DOA.


.

[WhiteoutWX]

24 minutes ago, nrgjeff said:

Greater KCMO area dews have been scoured by that MCS. Still low 60s Td but need upper 60s. LLJ is coming off ongoing convection; so, it will be impotent. Best chance for a spinner is a miracle up on the WF Missouri-Iowa border. It is decent terrain in contrast to much of Missouri, but the actual storms are subject to visibility challenges ongoing this week.

Other choices include chasing the DFW Metroplex, nah, and jungles east of the rest of the squall line, heck no!

The main problem yesterday was low level wind direction. VBV was in a tough spot; above 700 mb would have been easier to overcome. However, even with that crap, more backed surface to 925 mb winds would have done the trick. Just did not quite come together even with the LLJ. Hype accusations are not fair. Synoptic pattern was textbook. Come game day though, it's all about the meso-scale.

My secondary problem yesterday was boundaries did not work out. The US-160 boundary simply did not work. Felt like watching a basketball player go ice cold laying bricks. I'm shocked the OFB/DL bulge failed in OK. That's rolling your ankle in the game, lol. Both likely suffered from the not-backed low level winds. Glad it was just a virtual chase!

Surface winds were due southeasterly by 6 or 7 pm across most of central and southern Oklahoma ahead of the storms. Seemed pretty backed to me. However what I did notice as I was out chasing yesterday was just how light inflow winds were. I think that may have been a bigger contributor to failure than the wind direction itself.

[nrgjeff]

Yes very true. Southern OK surface was backed as all get-out. Problems might have been more at the lower meso level. Northern OK winds were kind of light relative to elsewhere. 

11 minutes ago, WhiteoutWX said:

Surface winds were due southeasterly by 6 or 7 pm across most of central and southern Oklahoma ahead of the storms. Seemed pretty backed to me. However what I did notice as I was out chasing yesterday was just how light inflow winds were. I think that may have been a bigger contributor to failure than the wind direction itself.

Maybe just fickle early May. Some years go 2003, 2007 and 2015 big. Other years go 2014, 2017 and 2018 crap-out. Late May is just more reliable. 2013 and 2016 went from nothing to nuts. With more thermodynamics, atmo is more forgiving of imperfections aloft. Late May might not have the big synoptic system, but subtle waves in southwest flow over 70 Tds is hard to beat.

[jojo762]

1 hour ago, the ghost of leroy said:

then don't hype it.  you're one of the guys here who most consistently gets a boner over forecasted events, putting out these massive posts listing off every parameter. lots of people were urging caution all along, or at least tempering their optimism.

Lmao. I'm simply contributing somethinng of substance to the board (unlike you), I definitely had several criticisms of the setup and not everything was hype. Everything I said was a representation of what models showed, in addition to what've I figured could happen. I wasn't the only one excited. Even SPC was mentioning tornadic supercells and strong tornadoes at D5... and the talk on twitter was easily more hyped than anything I ever said. Chill out dude.