2019-05-20 EVENT: TX/OK/KS

Jeff Duda

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The HRRR has been an outlier since it first came into range 24 hours ago. While it has verified better in the "discrete vs. linear" storm mode issue quite recently compared to the HREF members, it should still be noted that it remains basically at the far right end of the forecast uncertainty distribution. Last night's NCAR ensemble was also on board with an event resembling that from the HREF. Even the HRRRE forecasts from today have not been in total agreement with the deterministic member through the early part of tomorrow.
 
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Mar 30, 2010
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Good point Jeff. Just have to go off of what I have experienced with percentage verification. The HRRR has been pretty good this year from my experience. We're pretty much in monitoring day of event real-time data now and cross-referencing with model runs. I'm sure there are a lot of chasers gulping down late night coffee crunching the current data and latest runs as I am. The Oklahoma Mesonet is going to be a busy site tomorrow.
 

Dan Robinson

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Waking up early to see far less early storm coverage much farther north than models had indicated. That seemed to be the main failure mode threat of this setup, as heavy precip would reinforce the boundary across Oklahoma and keep the warm sector from advancing north, if much at all. Some HREF/WRF runs were showing it sagging south through the day as a cold front and keeping the main juice down near the Red River. Now, a much less contaminated warm sector looks possible if not likely.
 

Patrick K

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May 2, 2019
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Just my amateur opinion, and not many flies, but I see a few potential flies in the ointment. Firstly, the 500/700mb winds are almost perfectly parallel to the corresponding pressure contours and there appears to be at least some weakness in the profiles above 2-3km, so storm mode is probably going to be at least somewhat of an issue. Secondly, the environment is essentially uncapped beneath the warm front all day, and as Jeff notes, we expect several rounds of subtle warm advection initiation. This seems to be pushing the warm front more southward, but there are some model differences with HRRR lifting the warm front toward KS/OK border by 00Z and the NAM3km keeping a sharp stationary/cold front south of OKC metro by 00z. That said, advection below the front, wherever it is located, is aggressive.

During the afternoon initiation phase, I see storms over central into northern OK merging and generally becoming messy, developing in a SSW to NNE "tendril" and interfering with each other. This IMHO leaves a play on the southern edge of these "tendrils," TEC style. I would target Lawton OK as a starting point and watch how initial morning development unfolds. My expectation would be to keep an eye south and east with preference for any storm that can stay isolated east of I-44 as it moves NNE into the more favorable environment.

EDIT: has anyone seen the estimated rainfall totals through Tuesday, particularly from NAM and WRF? Stay safe out there!
 
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Jun 16, 2015
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I think the HRRR may have overcompensated just a bit with northward movement of the warm front, meaning I'm skeptical that the front gets far into northern Oklahoma, given a E/ESE moving convective complex in northwestern Oklahoma as of 8:30 a.m. I think it's reasonable to see the warm front get to roughly I-40 or slightly north of there, but watch convective trends closely.

In general, trends have been for a more discrete storm mode, even through early evening, along with a less contaminated warm sector. Trends still favor a few supercells eastward near the warm front into Arkansas.

The 12z MAF sounding is very telling, to see such a volatile, high-end environment already in place at 7 a.m., this far west. This air-mass will advect northeastward, toward the Caprock region/Northwest Texas into southwestern/south-central Oklahoma. This is where the greatest potential for significant, long-track tornadoes will likely occur. If we're nit-picking, it should be noted that the dryline orientation may be SSW to NNE near the Caprock, which is close to parallel with the deep shear vectors. This is why some of the high resolution guidance is a bit inconsistent with discrete cells vs. clusters/mixed storm modes. Ideally, you want a N-S oriented dryline with deep shear vectors showing more of a westerly than a southerly component. With that said, even without "perfect or ideal" wind fields, the significant, long track tornado threat remains.
MAF.gif
 
Jun 4, 2018
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So much like with Friday, I am limited somewhat by work today. However, I am hoping to be able to escape and get up towards either Abilene or Sweetwater, TX by 330- 400pm for a quick radar check before making a final decision from there. There are quite a few different flavors of northbound highways around there to help me adjust east/ west as I move north. With a pinch of luck, I'll be able to move up with any storms that have developed that far south. I seriously doubt I'll be able to make it up into OK before dark, and with work tomorrow as well, I will be somewhat limited to areas south of the TX/OK border. Best of luck and safe travels to everyone out there today. It could be a good one!
 
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Todd Lemery

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I’ll be targeting the dryline today where storms should be firing up around 3:00. HRRR has supercells remaining discreet all the way to nightfall. I’m not sure I’m buying that, but semi-discreet mode will work in a pinch too. Be extra wary on taking secondary roads today, especially to those targeting the warm front where lots rainfall has already softened up the roads this morning.
 

Dan Robinson

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Special soundings by the NWS and the COD teams are showing a significantly stouter capping inversion below 700mb than forecast, which is quite possibly the biggest enhancing factor development we've seen today. All of the possible failure modes of this event have vanished, and enhancing factors like more clearing (at least filtered sunlight in most areas) and now a stronger cap have really put this event into a top-level setup in terms of the environment.
 

Jeff Duda

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There's definitely something "off" about how this first round of storms is behaving. They're not acting like storms in "maxed-out" environment. We're definitely seeing rapid tendency for some level of storm rotation, but contracted low-level rotation doesn't seem to be materializing. Doppler velocities on the TX storms suggest the RFDs may be pushing through kinda hard, which may be limiting tornado performance at this time. Only the southernmost storm seems to be able to produce tornadoes right now.

As I Tweeted, I still think it's possible that storm competition can limit this event from reaching top-end performance levels. If there are just too many updrafts trying to pull in a finite amount of warm, moist air, and other storms are disrupting that, then there will be fewer tornadoes.

Things could also change as the afternoon wears on. While no area has cleared significantly, the environment in pretty much all of S OK remains undisturbed.
 

Patrick K

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May 2, 2019
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Jeff, I totally agree. There seems to be a storm mode issue given the deep shear vectors parallel to the dryline and pressure gradient, especially west near the greater forcing close to the dryline, as one would expect. But note the isolated cell in Kingfisher County that has gone bonkers, as should be expected given the environment. The unexpected capping inversion sampled at DFW seems to be a harbinger of more such cells later this afternoon. The HRRR has been more bullish on breaking out such cells, while NAM and WRF have been consistent for a while in a relatively undisturbed central OK getting blasted by messy storm mode around 00z.
 
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Jeff, I totally agree. There seems to be a storm mode issue given the deep shear vectors parallel to the dryline and pressure gradient, especially west near the greater forcing close to the dryline, as one would expect. But note the isolated cell in Kingfisher County that has gone bonkers, as should be expected given the environment. The unexpected capping inversion sampled at DFW seems to be a harbinger of more such cells later this afternoon. The HRRR has been more bullish on breaking out such cells, while NAM and WRF have been consistent for a while in a relatively undisturbed central OK getting blasted by messy storm mode around 00z.
 

Jeff Duda

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Not much in the way of new development east of the DL and south of the WF lately. Not exactly sure why (maybe just too much cloud cover), but given the next wave has popped down by Lubbock and storms now filling in from there up through NC OK, I'm starting to think the evolution upscale into a big line has already commenced.
 
Apr 23, 2005
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Not much in the way of new development east of the DL and south of the WF lately. Not exactly sure why (maybe just too much cloud cover), but given the next wave has popped down by Lubbock and storms now filling in from there up through NC OK, I'm starting to think the evolution upscale into a big line has already commenced.
NAM this morning was indicating some slight warming in the mid-levels through 00z, with 700 temps in the 10-12C range over SW OK, which appears to be verifying according to the SPC mesoanalysis page (and possibly also implied with the mid-day FWD sounding). Been wondering for awhile if this is the reason.
 
Jul 5, 2009
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...As I Tweeted, I still think it's possible that storm competition can limit this event from reaching top-end performance levels. If there are just too many updrafts trying to pull in a finite amount of warm, moist air, and other storms are disrupting that, then there will be fewer tornadoes...
MSD #710 (covering SW TX up through SE TX PH) bears this out:

“...So far, tornadic activity has been limited by the number of storms ongoing in relative close proximity...”

Impressive event so far, but fewer tornado reports and even warnings than I would have expected given the setup. But it’s still early, still a dangerous night ahead for residents.
 
May 6, 2005
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This could also be the classic case of "1 CIN in the 00Z OUN sounding is good enough to restrict CI because there is no other lift". We see that many times in C OK.
You may very well be correct. Seeing the 21z sounding had me worried, but it just diidn't materialize.


UPDATE:

And now we can compare to the 00z sounding. It was all there except that bit around 700 mb. Storms just couldn't push through. And no other forcing mechanism. The greatest outbreak that could have been.

 
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Jesse Risley

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Those lapse rates are scantily clad on that 0z sounding data, and I can't help but wonder how the ongoing cirrus impacted that, which I believe was a huge factor with the short-range models being overly magnanimous on the amount of uninhibited solar insolation that the warm sector was progged to experience. It does look like the main jet streak was a bit tardy so that, when coupled with the increased CIN (met on social media was noting that 700 mb temps increased by 8 degrees between 3 and 6 p.m. today per the afternoon balloon launch), kept much of the warm sector largely unmolested by storm activity through the daytime. The 0-6 km shear vectors were parallel to the surface boundary, and the baroclinicity along the NE-SW oriented boundary across NC OK was nothing short of a prodigious fly in the ointment.
 
Jun 16, 2015
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Lots of failure modes today, but a few rogue storms went to town and West Texas lit up, pretty close to what was expected down there. Forcing in the warm sector was weak to non-existent. There was a large area of extreme instability/favorable shear, from North Texas into southern/central Oklahoma. I wonder if the HRRR has a bias of overconvecting when there's marginal/minimal forcing involved. I know I've seen it a few times this year, most notably in southwestern Kansas. On the other hand, on the dryline day, it struggled to convect. Leitman mentioned how there was a bit of a 700mb thermal ridge over Oklahoma. I vaguely recall seeing this on mesoanalysis, but just assumed that it would advect east as the trough impinged on the High Plains. Too little, too late. Convective modes were messy. Outflow across Oklahoma started overtaking storms by mid-afternoon. What else?

There was also a case with some really funky hodographs. FDR was junky looking early on, especially in the mid-levels. 700mb winds were backing a bit over Oklahoma and although it did improve with time, it wasn't an ideal enough wind profile to support long-tracking tornadoes into southwestern Oklahoma. The MAF hodograph was awful looking in the afternoon too. Low-level shear in southern West Texas was marginal for most of the event, but with time, it did become more favorable toward and after 00z.

It's rare that you have an outbreak where the dryline, warm front AND warm sector all light up. We had two of those three go and then that random tornado northwest of Oklahoma City. As mentioned, the timing of the jet streak did slow down a bit. West Texas (northern part) could have lit up sooner, but the initiating boundary was just about parallel to the deep shear vectors.

All around, it was a complex setup. It was a case where the HRRR really did not perform very well at face value, but you have to wonder if it was just a small change/error in its initialized conditions that were enough to throw the warm sector into supercell-chaos. The parameter space was there, but high shear/high cape does not automatically imply a tornado outbreak, especially if there's little to no meaningful forcing.

A lot to learn and reflect on, but I'm glad that this event failed to meet expectations. The main reason being the large population center that was at risk, but also because of the extreme chaser convergence. It could have gotten really ugly, but thankfully it did not.

Personally, I think this event is leading me to try to be more objective and reasonably skeptical in the future. I almost always lean on the HRRR (not 100%, but a heavy lean), but now I may be a bit more skeptical. Also, even though I didn't practice what I often preach, an extreme parameter space does not automatically result in a supercell tornado outbreak.

End of rant.
 

Jeff Duda

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And now we can compare to the 00z sounding. It was all there except that bit around 700 mb. Storms just couldn't push through. And no other forcing mechanism. The greatest outbreak that could have been.
I saw at least one person tweet an OUN obs sounding today claiming [sic] "I have never seen such a tornado-supportive sounding".

Meh.

Certainly some impressive parameters, but consider a few things:
1) next to no shear between 2 and 4 km (actually, 0-4 km SRH < 0-3 km SRH due to slight backing between 3 and 4 km); if everything else went right, this would probably not be enough to restrict sig tors from forming, but...
2) likely subsidence inversion just above 700 mb; not only a CAPE robber (hurting vertical accelerations), but also suggestive of downward moving air in that layer, further restricting explosive development;

and perhaps most intriguing and subtle...

3) Very deep nearly-saturated inflow layer. I was involved in a lengthy Twitter discussion with another PhD meteorologist and severe weather expert:


...discussing the potential impacts of a deep layer with approximately d(theta-e)/dz = 0. It seems quite plausible that the effect of this feature was to allow for inflow parcels to originate at just about any level between sfc and the bottom of the inversion. Well, if parcels enter higher up then, 1) they aren't surface based anymore, and 2) those parcels pass through a much different shear profile on their way up with much less propensity to generate vorticity from tilting. Both of these factors, but especially #2, can complicate storm structure and behavior.

Again, details matter. You cannot claim "massive tornado outbreak" from just synoptic scale pattern + mesoscale situation (i.e., CAPE, shear, composite parameters maxing out).