2024-04-27 EVENT: TX/OK/KS/MO/IA

[Mikayla Norris]

I can't recall ever attempting to post in an EVENT thread with any more detail than "I plan to target X town", so please bear with me on this one. The CAMs seem to be coming into agreement with convection kicking off in western north TX and heading into SW OK as early as 12-15z, with some signs of it remaining discrete and robust. Both the HRRR and the NAM have some impressive parameters throughout SW OK at that time as well. This is from the 00z run of the NAM valid at 15z in SW OK.



I will be starting from home in Altus, OK, so my plan right now is to start bright and early and chase the early morning convection as it moves off to the NE. Later on around midday and into the afternoon, however, I'm still having trouble deciding on a target. Someone please correct me if I'm misinterpreting something, but on the most recent HRRR and NAM runs, both are showing the better parameters being off to the south and to the west of the OKC metro as far as instability, SRH, etc., and then pushing off to the east as the afternoon progresses. The CAMs are also showing discrete afternoon convection in that region, especially down towards the Red River. Following the morning storms, my thinking right now is to perhaps target somewhere along the I-44 or I-35 corridor, north of a line from Lawton to Wynnewood, but south of the metro. I'm sure that my plan will change again once I wake up tomorrow, and probably a million more times throughout the day, but I wanted to actually get something written down to keep myself honest and to hopefully force myself to improve my forecasting. Also, if I am mistaken on any of my above reasoning or am missing something meteorologically, please feel free to correct me!

 

[Jeff Duda]

In a broad sense, the setup for this one reminds me of 18 May 2017, which was a high risk bust across mainly OK. It featured a semi-compact shortwave ejecting over the plains in a manner not dissimilar to the shortwave impulse arriving tomorrow, also following right on the heels of a previous shortwave that prompted a moderate risk (success) two days prior in the same region. This particular shortwave appears to be lower in latitude by a few degrees and isn't as compact (or intense), but the low-level moisture already in place appears to be slightly better and further west.

The 2017 event was a bust primarily because storms went up really early (18Z initiation), which was before the wind profile could really "straighten out" from the typical morning spaghetti-like tangles that 12Z soundings tend to exhibit. Thus the initial storms consumed the good instability while struggling to produce tornadoes. A few longer-tracked supercells did occur, but I recall only one of them producing a photogenic tornado, and it was really only the one. There were TONS of storms, though, and competition was definitely a problem across most of the high risk area.

However, the convective scale forecast of this event differs from the May 2017 one. CAM forecasts of the May 2017 featured spatially dense and extreme UH tracks in the high risk area. Also, those forecasts did not contain a classic feature that I am seeing in the forecasts for this even - the overnight convective complex that develops over W TX between LBB and MAF (roughly 08-10Z) and then flies northeastward over NW TX and most of OK through the morning, usually departing the I-35 corridor by about 18Z. This seems to be the result of an arriving upper-level disturbance and its associated forced ascent first impinging on the very westernmost fringe of the high quality moisure, which has usually pushed back to the I-27 corridor by the overnight hours. This seems to be all it takes to fire up some strong (generally non-severe or only marginally so) storms that really push the limits on what kind of re-destabilization can occur behind it up to the northeast.

Most of the CAM runs I'm seeing (both deterministic flagships and ensemble members) indicate some degree of this evolution. The HREF is basically 100% all-in on this exact scenario. The NCAR MPAS ensemble, on the other hand, leaves TX and OK clean until afternoon CI. The NCAR C-SHiELD ensemble is more mixed, but several members are interestingly in between - firing storms near or just west of SPS around 12-13Z, which seems truly peculiar. Other members are "clean".

Some other experimental MPAS runs that NSSL are doing don't paint a great picture for chase prospects. Two of the configurations look like carbon copies of each other and are pretty pathetic:

Here's their corresponding early-day depictions:

These models tend to wipe out most of the region, but leave the fringes open for rotating storms. That basically results in a widespread mess from about I-20 to possibly as far north as I-80:

Even the experimental RRFS, which does not contain early-day convection and does develop afternoon supercells in OK, doesn't persist them for terribly long:

The RRFS does go ape-shit on the warm front, though; it is one of the few that does:


Without droning on too long, I definitely see some flies in the ointment on this setup, and I'm not surprised SPC has held off on even going moderate risk for this event. There is a lot of uncertainty as to a huge fraction of the environment being wiped out early, and also to storm coverage and location later on. If the TX overnight convection never materializes, that could imply the wave has not yet arrived, which could imply that it is late in ejecting. Thursday (the 25th) seemed to underperform a bit, and I suspect it is because the wave ejected too late. Perhaps that may have influenced the timing of this next one so that it might also arrive a bit late, and after the best destabilization has manifested.

I don't know how this will play out. But I don't see it as a slam dunk event.

 

[Mark Gressman Jr]

I can't add much more than what Jeff touched on, but the SPC has now issued a moderate for C Oklahoma. I wonder if that is in response to the over performance of yesterday's events. At this point there's discrepancies with models in respect to cloud cover, but most do break out convection in C Kansas near the triple point. The last several runs of the NAM 3K have moved the low further south than my previous forecast, and shear looks less impressive, but I still like somewhere near Great Bend as a starting point.

I also wanted to point out for the newer members who might be learning from these forecasting threads (they've been a huge help in my own understanding)... when looking at forecast soundings and the Omega bar readings on the left are clearing the dashed lines, it's considered to have convective contamination. My understanding is that the parameters in the sounding aren't necessarily indicative of the surrounding atmosphere, and the user should take that into consideration when making decisions.

 

[JamesCaruso]

I was just watching a Convective Chronicles forecast video that was done on the morning of Friday 4/26 for both 4/26 and 4/27. Trey cited the meridional flow as a potential negative for Saturday, which I understand and had already mentioned in my own post above. But wasn't there also meridional flow yesterday the 26th? I'm assuming the low-level shear and cold core setup more than compensated for it, but I'm curious as to why Trey didn't even mention it in his forecast for 4/26. I'm just trying to make sure I understand why/when meridional flow is and isn't an issue.

 

[Jamie H]

I would think the SPC isn't swayed by pervious events, but I could be optimistic!

I am surprised that some of the CAMs are showing little going on as a check of the 09Z RAP shows quite the parameters across OK from around 18Z onwards. The MPAS experimental has been working quite well so far this year I think and the partial 12Z RT version looks promising though hasn't fully come in yet.

I'm sure I am missing something key due to relative inexperience, but given the possibilities, Central OK seems like the place to set up today.

 

[Mikayla Norris]

I don't know the last time I was sitting under a newly issued tornado watch this early in the day, and I'm still at the computer having my morning coffee. The first half of my plan for the day remains intact, chase the morning storms to see what I can see. After that I guess we'll see what happens. I have a sort of outline in my head, but I'm going to remain flexible. Stay safe today folks!

 

[Jeff House]

As of 9am Central time I discern three obvious boundaries. Synoptic WF is north of KCMO. Clearly outflow is in southeast Kansas. Gravity wave or other OFB is down in Oklahoma south of I-40. I'm using the surface chart and early visible imagery. Dry line will punch out into these boundaries, along with perhaps other subtle boundaries.

Hodographs are not textbook, but there is plenty of turning with height. Some concerns on storm mode and movement are noted along the DL or pre-frontal trough. However there will be just enough orthogonal component. Low level shear will more than compensate for any upper hodograph kinks or extensions straight up. Pattern recognition with all those boundaries enhancing low-level shear / SRH calls for the robust outlook.

 

[Dave C]

I can't add much more than what Jeff touched on, but the SPC has now issued a moderate for C Oklahoma. I wonder if that is in response to the over performance of yesterday's events. At this point there's discrepancies with models in respect to cloud cover, but most do break out convection in C Kansas near the triple point. The last several runs of the NAM 3K have moved the low further south than my previous forecast, and shear looks less impressive, but I still like somewhere near Great Bend as a starting point.

I also wanted to point out for the newer members who might be learning from these forecasting threads (they've been a huge help in my own understanding)... when looking at forecast soundings and the Omega bar readings on the left are clearing the dashed lines, it's considered to have convective contamination. My understanding is that the parameters in the sounding aren't necessarily indicative of the surrounding atmosphere, and the user should take that into consideration when making decisions.

I'm glad you pointed out contaminated soundings. I have seen a lot posted lately. The same is true for cherry picking soundings. I'm far from the best forecaster out there, but trends and averages (between models, over space, and over consecutive runs) have a much better utility in accurate targeting in my experience than poking about for extreme parameters in one run and relying too heavily on such results.

Back to todays setup. Semi meridional flow were a concern both yesterday and today, but both days had high low level shear and large low level instability which should mitigate to an extent that concern, as mentioned by James and others. latest runs show steering heights today moving off the southern dryline axis by at least 15 degees, which could maitain clusters or an ocassional discrete throughout OK and TX. Initial convection is demonstrating very linear behavior so far though.

Outlfow placement should be something to watch for the second round of initiation. If I could be out, I would be targeting Sayre to S of Wichita based on helicity tracks consistency on multiple runs. The entire area is saturated with instability and strong low shear, so it is just about positioning for good road network and likely initiation and track.

 

[Dan Robinson]

Currently in Ottawa, KS still indecisive about where to go. Central Oklahoma looks like the most solid of the targets, but being a big day on a Saturday near OKC, I'm more inclined to look for something elsewhere. The warm front along I-70 in Kansas is a possibility, but the strong northerlies on current obs makes me concerned that is going to either turn into a cold front by itself and/or get reinforced by outflow quickly to the same result. The boundary looks to be in better shape farther east, but I'm concerned about clouds and precip fouling that area. I may end up biting the bullet and going into Oklahoma like everyone else though. The current MCS doesn't look like it is going to plow east and wipe everything out (yet). I'm also considering playing the northern end in southern Kansas where the current MCS is shown potentially separating into supercells.

 

[James Wilson]

Dan are you not concerned about the storms to the South Holton moisture to the north? I just drove through Ottawa and I'm heading down to get on the Storm by Enid I feel the parameters are coming together pretty good down there as opposed to Kansas

 

[Blake Naftel]

A complicated and muddy forecast analysis this morning with some atmospheric hints already to shape up. Will keep this brief. Currently in the Overland Park/KCI region with a FFZ [forecast focus zone] of north-central Oklahoma northeast to the Kansas border [Blackwell/I-35 towards Winfield] for mid/late afternoon, in favor for surface recovery and convective re-generation along a proposed outflow boundary hinted by several CAM’s. In real-time, the tornado warned supercellular convection, presently from Enid SW to Elk City, will be interesting to watch evolve; along with the mesoscale environment and attendant recovery as those storms populate northeastward into Kansas.

The 12Z OUN upper air sounding [actual, not simulated] is "loud and clear" in terms of potential tornado production for however the atmosphere evolves in NC/NE OKLA and SE Kansas today. Would be interested to see if a special sounding is released at ITC or TUL. Another region of potential interest is closer [to my present location] along Highway 75 from Osage City to Yates Center, KS for a rapid re-evolution with the present convection moving northeast for later today. All is rapidly materializing for a classic, frustrating high-end potential day either way. Shall see what transpires.

Will note for anyone chasing in Southeastern Kansas; numerous local and highway zones in specific areas [such as HW 59 north of Parsons and east of Chanute] were closed on Friday, likely due to flooding. Wise to keep a heads up on that aspect today! Good luck to all out and be safe. Busy day ahead!

 

[Mike Smith]

Would be interested to see if a special sounding is released at ITC or TUL.

Blake, just as an FYI, TUL and ITC are not rawinsonde stations. Lamont is a non-NWS rawinsonde station which sometimes releases at 17Z. Hope they will today. I'm sure OUN will.

 

[Dan Robinson]

Dan are you not concerned about the storms to the South Holton moisture to the north? I just drove through Ottawa and I'm heading down to get on the Storm by Enid I feel the parameters are coming together pretty good down there as opposed to Kansas

So far, it looks like those aren't surging east too quickly, so hopefully 50 miles or so north of the border east of 35 will remain viable. The anvil blowoff from that complex is more concerning now - in the past hour, it's really expanded east. I'm also not a fan of hours-old established blobs that eventually decide to go tornadic, as it seems they are more likely to be HP at that point. I'd prefer a new storm somewhere east of the current activity that will interact with the OFB that Jeff alluded to (although it's not as easy to pick out now on vis/radar). The HRRR hints at some lead storms firing down along I-40 west of OKC that may be players in that regard as they approach the KS border. I'm going to go ahead and drop south just to see what this current storm passing south of Wichita will do. Not expecting it to be a show, but at least it provides a position for several options later.

 

[Jeff House]

Northeastern Kansas low level winds should not be impeded by the convection in south-central Kansas, at least not before the NE KS stuff can get going and get rooted. And the 70/60 Tor watch is out.

Northwest Missouri should be considered. It's still decent terrain. Little hilly coming out of the Missouri River Valley; then, it gets decent again.

 

[Jeff Duda]

Just an analysis of what I currently see:
The cloud cover overspreading C KS in response to the building convective cluster across N OK is concerning as far as getting widespread high intensity storms in C/NC KS later today. I would bet that all areas along and south of I-70 have basically reached their daytime high by now and will not destabilize any further. Thus, they're dependent on kinematic disturbances for CI from here on out, at least until the larger forcing for ascent with the wave arrives this evening (after which, who knows what the thermodynamics will look like). They're already at 2000-3000 MLCAPE in that area, with 40-60 kts of effective shear, so the environment looks good for any updraft that goes.

EXCEPT...the 0-3-km shear field doesn't presently resemble an outbreak look to me:

I'm not sure what's causing that dearth of shear in S/C KS, nor if the increased shear in NC OK is causing the convection there or being caused by it.
The corresponding 0-3-km SRH field does not look particularly impressive. Effective SRH also looks meager. I'm sure those values will increase throughout the day as the upper level disturbance moves over the area and the wind fields respond. Ultimately, storm evolution will depend on the existing coverage by the time the wind fields improve. Will the storm mode still be cellular? Will there be large regions that have been convectively overturned? That is my concern especially with C/NC KS. E/SE KS through C/E OK look to remain open for a few hours.

The latest HRRR runs suggest the best show will develop SSW of the existing convection along the dryline from W OK into NW TX through 00Z, with little to no sustained open warm sector development east of there. Storm coverage may end up being pretty high, which may end up resulting in unfavorable interference and competition in determining which storm(s) will become dominant. The biggest UH signals continue to be with the extension of the existing convection as it evolves through E/SE KS later on, though, which may end up being the place to be.