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

Jeff Duda

Resident meteorological expert
Staff member
Oct 7, 2008
2,954
1,431
21
Westminster, CO
www.meteor.iastate.edu
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.
BTW, I'm going to start tooting the shit out of my own horn here, because I feel reasonably vindicated with just about every post I made in this thread. But the one quoted above is most prominent to me, and it's one I want everyone to pay attention to.

I know most of you here are not degreed meteorologists and are not researchers and thus are not totally informed as to all the tools out there. Thus it makes sense that so many of you seem to live and die by the HRRR, since it is arguably the most prominent CAM (and, in fairness, it does tend to provide a lot of helpful information and value for forecasting over non-convection-allowing models). However, it is not the only CAM out there, and is not even the only operational CAM. Those of you not already familiar with the HREF need to become familiar with it. Start here: SPC HREF viewer site

The 3 km NAM is a member, as is the HRRR. The HREF gave a lot of clues that this event may not turn into a massive tornado outbreak all the way from when the first members had this event in range.

While non-operational, the NCAR ensemble is running for the next few weeks as part of the HWT spring forecasting experiment in Norman. This happens every year. NCAR Realtime Ensemble Forecasts

Also, the HRRR has an ensemble component: HRRRE viewer site

Familiarize yourself with these other CAMs and CAM ensembles, because many of them will stick around, and one of them is bound to eventually supersede the HREF as it currently exists.

It would be unwise to cherry pick the HRRR or wishcast off of it. The most sensible thing you can do as a forecaster/chaser is to collect all the information you can and make a decision based off of the consensus of that information, not just the sexiest voice.
 
Mar 30, 2010
32
6
11
BTW, I'm going to start tooting the shit out of my own horn here, because I feel reasonably vindicated with just about every post I made in this thread. But the one quoted above is most prominent to me, and it's one I want everyone to pay attention to.

I know most of you here are not degreed meteorologists and are not researchers and thus are not totally informed as to all the tools out there. Thus it makes sense that so many of you seem to live and die by the HRRR, since it is arguably the most prominent CAM (and, in fairness, it does tend to provide a lot of helpful information and value for forecasting over non-convection-allowing models). However, it is not the only CAM out there, and is not even the only operational CAM. Those of you not already familiar with the HREF need to become familiar with it. Start here: SPC HREF viewer site

The 3 km NAM is a member, as is the HRRR. The HREF gave a lot of clues that this event may not turn into a massive tornado outbreak all the way from when the first members had this event in range.

While non-operational, the NCAR ensemble is running for the next few weeks as part of the HWT spring forecasting experiment in Norman. This happens every year. NCAR Realtime Ensemble Forecasts

Also, the HRRR has an ensemble component: HRRRE viewer site

Familiarize yourself with these other CAMs and CAM ensembles, because many of them will stick around, and one of them is bound to eventually supersede the HREF as it currently exists.

It would be unwise to cherry pick the HRRR or wishcast off of it. The most sensible thing you can do as a forecaster/chaser is to collect all the information you can and make a decision based off of the consensus of that information, not just the sexiest voice.

Toot away, Jeff, toot away. I stand corrected. I was one of the guilty parties. Always you can learn something from events like these.
 
  • Like
Reactions: Shane Young
Apr 10, 2008
59
16
11
28
Lexington, MA
isaac.zpato.net
3) Very deep nearly-saturated inflow layer. I was involved in a lengthy Twitter discussion with another PhD meteorologist and severe weather expert:

I really appreciate your posts. I thought that the 21Z OUN looked pretty odd with the moist layer extending up to almost 600mb! This theory regarding why that may have been an issue makes a lot of sense to me.
 
May 6, 2005
231
91
11
Moore, OK
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).
Jeff this lines up with the satellite presentation on the storm from El Reno toward Crescent. Even though that storm did produce a tornado, while lookin at it on satellite it never had that explosive look. The anvil never really spread out which told me it was struggling somehow. The 1-min and 30-sec meso sector yesterday was a great tool to look at. The storm did have a decent radar presentation while producing a tornado, but it never had that explosive satellite look.
 
  • Love
Reactions: Shane Young
May 1, 2005
58
6
11
36
Orlando, FL
Up along the warm front by evening, Sunday night's HRRR actually didn't end up seeming to be too far off in terms of having some exciting strings of structure eventually... it's just that the outflow was 10 miles out of ahead of just about all the mature storms by that point. [Don't suppose anyone knows any sites that hold HRRR graphics longer than a day, other than the work needed to translate the GRIB at http://home.chpc.utah.edu/~u0553130/Brian_Blaylock/hrrr_FAQ so a better side by side reflectivity comparison can be shown for that time rather than the broad time frame of the run-max plot I happened to have?]

Some of the forecasted supercell structure within the line for the late evening period certainly caught my eye in the Sunday evening HRRR run (perhaps because I'm outside the region for the event and so not focusing on chase targets... I didn't check whether they were surface based by then?) And seemed those elevated storms did at least do reasonable at verifying their anticipated structure once they got the extra oomph/focus of the boundary... so perhaps Jeff/SRHelicity's option #3 (also echoed by Jeff Snyder on FB/Twitter) of the saturated low level parcel proves most notable indeed? Certainly going in the memory banks, and would be interested to see if studies show it as a major trend that needs to be included in severe weather parameters?

18225


(The HRRR did also actually seem to do relatively well [from what I can remember] in the Sunday evening run with the positioning of the warm front compared to the 3km NAM, which instead brought it up further on into southeast Kansas for a little while during the afternoon [the NAM seemed more an outlier in that regard]. Plus perhaps was pretty good with the potential in eastern Oklahoma and SW Missouri, if the MUH plot may be suggesting that?)
 
Last edited:
  • Like
Reactions: Eddie Natenberg
Jul 5, 2009
808
471
21
Newtown, Pennsylvania
BTW, I'm going to start tooting the shit out of my own horn here, because I feel reasonably vindicated with just about every post I made in this thread. But the one quoted above is most prominent to me, and it's one I want everyone to pay attention to.

I know most of you here are not degreed meteorologists and are not researchers and thus are not totally informed as to all the tools out there. Thus it makes sense that so many of you seem to live and die by the HRRR, since it is arguably the most prominent CAM (and, in fairness, it does tend to provide a lot of helpful information and value for forecasting over non-convection-allowing models). However, it is not the only CAM out there, and is not even the only operational CAM. Those of you not already familiar with the HREF need to become familiar with it.....
Jeff, not to speak for everyone but I’ll venture a guess that we all appreciate not just your technical knowledge/contributions but also your measured conservatism that helps us keep our hopes and expectations in check!

Also your comment about us non-mets not being informed on all the tools is dead-on. This is something that often frustrates me. I have a hard enough time keeping up on developments in my own field of finance and accounting, not to mention developments in the industry I happen to work in (home healthcare), so how the hell can I also keep up on all the modeling changes, biases, etc.? I don’t even have the background in math, physics or meteorology to understand enough about them even if they weren’t changing so rapidly every year. The suggestions and links you provided are a big help, and it would be great to get a separate thread going on the state of the current tools and their biases. I am sure this exists somewhere, but I’m talking in layman’s/chaser’s terms.

Anyway, I’m glad I didn’t drive myself nuts about missing yesterday or trying to fly out there just for that. There is always more downside than upside in events like this. If some of the storms went to town as they did, even with the limiting factors mentioned above, that goes to show how incredible the dynamics really were. It could have been much worse, so we should be happy for the folks that live in the area. Although from a chaser’s perspective the outbreak was somewhat disappointing, it also shows that you don’t need an outbreak to have a great chase day. You can generally only chase one supercell at a time anyway, so as long as you’re on one, who cares how many other ones are happening??
 
Granted I didn't spend much time studying this event since I knew I could not chase (my whole season is non-existent thanks to my new career as 'starving artist') but I'm a bit puzzled by all the pooh-pooing of the forecast yesterday. A good percentage of high risk days never produce photogenic EF-4s. If you look at the report map, it certainly looks like it could qualify as a regional outbreak. I'm sure the chase sucked for most but honestly looking at radar signatures the morning HRRR forecasts seemed pretty spot on to me...they captured the mess in OK and the discrete cells in TX, and the forecast in general was pretty good in delineating the aerial threat. It's easy to get excited and wish-casty about any day with big parameters--its just as easy to afterwards say 'i knew it' that the atmosphere doesn't always obey your wishes.
18229
 

Jeff Duda

Resident meteorological expert
Staff member
Oct 7, 2008
2,954
1,431
21
Westminster, CO
www.meteor.iastate.edu
BTW, the way convective outlooks get verified is by something called Practically Perfect (Hindcast/forecast), or PPF. A few websites out there mimic this behavior, but because they differ on specifics of the equation, you get somewhat different results. Here are the results for the tornado aspect of yesterday's forecast:

This one appears on Victor Gensini's website: SPC Practically Perfect Hindcast (with an archive that goes back a fair ways)
tornado_current.png

This one is available on the St. Louis University's CIPS website (CIPS Real-Time SPC Practically Perfect Forecasts)
201905211200_ppfTorn.png

This other one is not available to the public, but is an example of what goes on at the spring forecasting experiment at the Hazardous Weather Testbed in Norman:
Screen Shot 2019-05-21 at 12.49.29 PM.png

Note that the above will not include any hatching for significant reports due to EF-scale ratings not known at the time of image creation.

You can see clearly here that, even in the most friendly scenario, only a moderate risk would have verified for tornadoes. In more conservative cases, barely and enhanced risk would have verified.

It is possible that some tornadoes occurred for which LSRs (on which these PPFs are based) have not been issued yet, so technically this could change in the future, but it will take months before Storm Data's official count for this event is released, so for the time being, this should be considered very close.
 
Jun 16, 2015
407
867
21
32
Oklahoma City, OK
quincyvagell.com
Last edited:

chrisbray

EF4
Apr 24, 2012
471
125
11
Bourbonnais, Illinois
BTW, I'm going to start tooting the shit out of my own horn here, because I feel reasonably vindicated with just about every post I made in this thread. But the one quoted above is most prominent to me, and it's one I want everyone to pay attention to.

I know most of you here are not degreed meteorologists and are not researchers and thus are not totally informed as to all the tools out there. Thus it makes sense that so many of you seem to live and die by the HRRR, since it is arguably the most prominent CAM (and, in fairness, it does tend to provide a lot of helpful information and value for forecasting over non-convection-allowing models). However, it is not the only CAM out there, and is not even the only operational CAM. Those of you not already familiar with the HREF need to become familiar with it. Start here: SPC HREF viewer site

The 3 km NAM is a member, as is the HRRR. The HREF gave a lot of clues that this event may not turn into a massive tornado outbreak all the way from when the first members had this event in range.

While non-operational, the NCAR ensemble is running for the next few weeks as part of the HWT spring forecasting experiment in Norman. This happens every year. NCAR Realtime Ensemble Forecasts

Also, the HRRR has an ensemble component: HRRRE viewer site

Familiarize yourself with these other CAMs and CAM ensembles, because many of them will stick around, and one of them is bound to eventually supersede the HREF as it currently exists.

It would be unwise to cherry pick the HRRR or wishcast off of it. The most sensible thing you can do as a forecaster/chaser is to collect all the information you can and make a decision based off of the consensus of that information, not just the sexiest voice.
Hi Jeff,
I always appreciate the knowledge you bring. I saw on the discord that the 4/27/11 BMX sounding had a nearly identical thermal profile as OUN yesterday. Why would deep saturation hurt yesterday while not hurting 4/27/11?
 
May 6, 2005
231
91
11
Moore, OK
Hi Jeff,
I always appreciate the knowledge you bring. I saw on the discord that the 4/27/11 BMX sounding had a nearly identical thermal profile as OUN yesterday. Why would deep saturation hurt yesterday while not hurting 4/27/11?
Same thing Jeff on the 00z Lamont sounding for the 4/14/12 outbreak. The 4/14 storms all formed along the dryline so they had a forcing mechanism to get them going. And once tapped into the deep surface theta-e air they were able to be fully maximized. Not too sure on the BMX sounding. I would like to see what the 00z sounding looked like. SO here it is:



Notice the warm temps/cap at 700 hPa has dissapated by 00z. Also, the moisture depth doesn't go all the way up to 700 hPa like it did on the 18z. So I think comparing 18z BMX and 00z OUN isn't fair.

Here is the 18z BMX sounding:

 

Jeff Duda

Resident meteorological expert
Staff member
Oct 7, 2008
2,954
1,431
21
Westminster, CO
www.meteor.iastate.edu
Hi Jeff,
I always appreciate the knowledge you bring. I saw on the discord that the 4/27/11 BMX sounding had a nearly identical thermal profile as OUN yesterday. Why would deep saturation hurt yesterday while not hurting 4/27/11?
I don't honestly know these answers. This is a lot of science-based speculation that has yet to be tested or verified with obs or even models.

Other things to consider are that storms never even really got going in S/C OK, yet they were prevalent on 4/27/11. Differences in wave timing, cloud cover (similar cloud cover seemed evident on 4/27/11, but it's hard to quantify this in a detailed sense) could have also helped. There also wasn't much in the way of synoptic scale convergence in the surface flow yesterday.

When it comes down to it, deep moist convection is very sensitive to thermodynamic changes. It could possibly be that temps were a mere few tenths of a degree too cool at the surface or too warm somewhere aloft that was just enough to keep a plume from going nuts. It's pretty hard to say without more extensive testing.
 
  • Like
Reactions: Shane Young