2013-05-31 EVENT: KS, OK, MO, IL

[Karen Politte]

What confused many of us there at the time was that the entire large rain curtain zone *was* the tornado. That was only evident when that entire zone became the wedge after crossing 81. Everyone was focused on what was condensed, which was a major contributing factor to what happened.

It seems clear to me from the data that most of us who thought we were in inflow were in the tornado itself, if just the outer edge. I'm anxious to see the RaxPol data with timestamps which will prove or disprove this.

Dan posts what I think is one of the most astute observations on this tornado. I think I saw this most evidently from watching Jeff Piotrowski's video of the event (I believe he documented it from I-40 - regardless he was always north of the circulation). After the multivortex stage, when the tornado and parent circulation begin to "change" modes, and wrap the wet RFD around, you can see the violent motions in the wet RFD/atomized rain that the condensed part of the circulation is wrapping. It's like a fragmented debris-fan of cloud/precip around the tornado. I've never seen motion and structure like that in a tornado before - it was as if the condensed tornado funnel was just the "core" of the larger tornadic circulation it was embedded in - but the lack of condensation visible in the wider area of tornadic winds really seemed to be what caught a lot of folks off-guard.

In the end, what Dan mentioned about the difficulty in delineating between inflow/wet RFD and actual tornado is the crux of the matter. To do so on a tornado of this magnitude and varying size/shape is even more difficult, even without the insanely fast expansion and turning/acceleration of the circulation. What a horrible, horrible storm.

KP

 

[David Williams]

This continues a discussion I started in another thread. I'll copy and paste my question:

"I, like many others, was caught at El Reno rd and highway 81 when the tornado began to expand and turn north. I have been trying to piece together my experience, and I was hoping to get some input from the more experienced chasers and from anyone that had a better view of the storm than I did from right under it. After waiting my turn to go south from El Reno rd onto 81 I was only able to drive for 10 or 15 seconds before I noticed through the rain a large vortex moving ne toward me from only a few hundred feet away. I, and the other drivers/chasers around me, quickly put on the brakes and went in reverse to let the vortex pass in front of us (I'm not sure if this is the same vortex that hit the Tornado Hunter vehicle but I did notice the next day when I drove through the damage path that he was very close to my position at that time.) Many of the other vehicles stopped after the vortex passed in front of us on the road. However, recognizing the transparent rain bands/condensing tornadic circulation and debris in the air I knew we weren't done with the tornado yet. So, I drove south as fast as I could. I passed a parked police car and what looked like a Dominator; however, I couldn't look too closely because a power line was down in front of me and I had to drive into the median to get under it. With the highway clear, I blasted south. Unfortunately, I also got blasted by some intense wind from the west. In a matter of moments debris was flying across the road and my windows were blown out. Fortunately, I made it out of the RFD after about a 1/2 mile with only a scratch on my cheek.

So, my question is where did the tornadic circulation end and the RFD begin? I understand that this question may not be accurately answered because of the nature of this rare beast. But, I am trying to wrap my head around what happened. I clearly got caught inside the tornado at El Reno and 81 because this is the exact time when the tornado expanded and made its northern turn. Also, I had to reverse (move north into the larger tornado) in order to avoid getting hit by a large vortex. The wind was strong during that time; however, it wasn't until I passed the cop car and downed power line that the wind started really moving (granted I was able to accelerate faster but the force was a noticeable increase from the west) and this is when the debris very much like Brandon and Brett drove through started flying across 81. Anyone that drove 81 that day or the next would have noticed the mile or more of debris caught in the fence and rail guard along the road.I have watched many of the videos in the reports section, and many videos show what looks to be a clear slot far south of the tornadic circulation. Anyone with any feedback, ideas, or stories please chip in."

 

[Jeff Snyder]

What confused many of us there at the time was that the entire large rain curtain zone *was* the tornado. That was only evident when that entire zone became the wedge after crossing 81. Everyone was focused on what was condensed, which was a major contributing factor to what happened.

It seems clear to me from the data that most of us who thought we were in inflow were in the tornado itself, if just the outer edge. I'm anxious to see the RaxPol data with timestamps which will prove or disprove this.

So, my question is where did the tornadic circulation end and the RFD begin?

Dan and David -- It's very difficult to determine where the tornado "ends" and the RFD "begins" in our data. The only logical "zone" where one can confidently say that one is outside the tornadic flow and into RFD is 3.5+ km south of the center of the tornado when we were collecting data at Banner Rd and I40 in the 6:24-6:25 period. The actual debris field is quite a bit smaller, but we know that the debris signature evident in Zdr and Rho_hv isn't necessarily where the tornado "is" since many weak tornadoes have little or nothing in the way of a debris signature (and it stands to reason that weaker winds beyond the radius of maximum winds may not be strong enough to loft debris that leads to the polarimetric debris signature). The circulation was massive by the time the center crossed 10th St / Reuter with >60 m/s winds extending several km southeast of the center of the tornado. Unfortunately, as a result of the very strong inflow that we experienced in the notch of the hook as we were driving E on I40, we weren't able to collect data between ~6:18 and ~6:24 pm. The circulation wasn't particularly large before that data gap, and it was massive by the time we were up and scanning again.

I don't know where you were when you experienced the extremely strong winds that resulted in your own injury/injuries, but it may have been within the periphery of the tornadic circulation (even though the condensation funnel/funnels was/were to your northwest).

 

[JamesCaruso]

What confused many of us there at the time was that the entire large rain curtain zone *was* the tornado. That was only evident when that entire zone became the wedge after crossing 81. Everyone was focused on what was condensed, which was a major contributing factor to what happened.

Dan, this is interesting to contemplate and to try to understand... Is this just a function of the meso being so close to the ground - i.e., these wrapping rain curtains were created by the same mechanism we normally see forming the "hook", except that the meso was just lower? When you say the "entire zone became the wedge" - since in your view this zone was already the tornado, I assume here you are talking about condensation into the visible wedge? But how would rain curtains turn into a condensation area, isn't that moving "backwards" in terms of the continuum of condensation/saturation?

Jim

 

[Dan Robinson]

Jim, the best visual of this event that I've seen is Jeff Piotrowski's video here: http://www.youtube.com/watch?v=KX8o2loAMhY

At 3:32 in the video (which is looking south/southwest), you can see the condensed barrel vortex on the west side of the tornado. The tornado is in the vicinity of crossing Highway 81 at this time (or has just crossed). The eastern side appears as a large area of rain curtains.

Then look at the tornado at 4:01. The rain curtain zone (the eastern 2/3rds that was visible at 3:32) is now entirely condensed into a wedge. At 4:01 in Jeff's video, the tornado is in the vicinity of crossing NW 10th/Reuter Road. There is obviously a minute or two gap in between what you see at 3:32 and 4:01 due to the clip being edited, but the transition between those two states took roughly two minutes or less.

 

[Dan Robinson]

Deleted for now. I found more errors in the data that will need time to be corrected and verified.

 

[Jeff Snyder]

Dan -- Are the times you presented corrected for the clock error(s) you mentioned? The tornado was still a ways W of US81 at 6:13 pm. When we're just getting onto the eastbound I40 entrance ramp from US81 around 6:18 pm, the center of the tornado was still just W of 81 or maybe right at 81, with the northernmost edge of precip in the hook echo still S of Reuter/10th.

 

[Dan Robinson]

Jeff, I just discovered (of course, after posting this) that my cameras are not keeping consistent time when they are turned off. The time in between the above events is correct, but will need to be shifted once I can get a good reference point for at least one point.

 

[Dan Robinson]

My GPS log shows times 8:28 later than these. I had originally written that off as a problem with the converter software glitch, but it now appears the discrepancy is with the cameras, and the GPS log is correct.

 

[Dan Robinson]

Deleted for now. I found more errors in the data that will need time to be corrected and verified. I will have to tackle this on another night.

 

[Jeff Wright]

Reminds me of the Tuscaloosa tornado as it moved just north of Birmingham http://www.youtube.com/watch?v=NOgO94QFKvo

 

[Juston Drake]

Now that the death ridge is setting in, I have some time to share something that Simon and I noticed while looking at radar data on our way back from our last chase. I was rather intrigued by the fact there was an EF2 anticyclonic tornado occurring, while the mega wedge was ongoing, so I looked back at Level II data to see if I could find the anticyclonic couplet with the preliminary times the NWS provided for the tornado. What I found was rather amazing and something I haven’t seen this prominently on radar before.

At 23:10Z: The supercell has a pronounced hook at the 0.9 tilt (the upper left hand image) and a noticeable hook and bounded inflow notch at the 4.0 tilt (the lower left hand image). Note the strength/size of the RFD, which would be the inbound velocities in the SRV image on the upper right hand image at the 0.9 tilt.

At 23:15Z: The RFD in the SRV image has gotten stronger and started to become much larger in size. On the base reflectivity image at the 4.1 tilt, there is still a distinct inflow notch and a pair of hooks is becoming more evident.

At 23:20Z: On base reflectivity at 4.1 tilt, the supercell has a pretzel shape, with a very distinct cyclonic and anticyclonic spiral pair evident in the precip field. In the SRV image, the RFD is reaching it max in strength and size and is hardcore punching in.

A zoomed out and larger view of the pretzel shape of the El Reno supercell at 23:20Z from 4.1 tilt.

At 23:29Z: On SRV at 0.9 tilt, the cyclonic and anticyclonic couplets are visible, which is when the NWS has the anticyclonic EF2 tornado SE of El Reno starting. Also of note, the RFD by this point has gotten a lot more concentrated and is being funneled between the cyclonic and anticyclonic couplets. The base reflectivity image at 4.0 tilt show a weak echo region where the strong RFD punch has occurred between the pair of couplets. The echo tops image (lower right hand corner) show there are two different updrafts, one associated with the cyclonic meso and the other associated with the anticyclonic meso.

Being able to see the "RFD punch" cut into the meso and split it up into a cyclonic and anticyclonic pair this easily on radar is amazing to me! I have seen this process visually, while chasing, occur many times during the occlusion process, but I don’t remember ever seeing it this well on radar. I can only imagine what radar data the RaXpol radar was able to get if I can see processes like this that well on the 88D radar. The storm scale dynamics that were occurring within this storm were off the charts, as well as the environment it formed in, which is why I find this particular supercell so fascinating. After doing some rough calculations of the effective EHI values in the immediate area, taking into account the CAPE values from forecast soundings and playing around with the hodograph in BUFKIT by changing the surface winds to what they were on a surface map and using the 0z OUN sounding, the effective EHIs were between 18 – 24....historic values…..and possibly the highest we have ever seen! With these type of conditions and the supercell taking full advantage of that kind of environment, it is not surprising that it produced such a violent and record breaking large tornado.

 

[Dan Robinson]

Juston, that's very interesting - that anticyclonic couplet is at the exact time and place that my rear window was blown out (and I was slightly injured) in the RFD on Reuter road. My video cameras show winds out of the west-southwest that suddenly turn westerly at the time the window blows out. I can't see any evidence of a ground circulation in either my side or front cameras, just continuous westerly/west-southwesterly winds with intermittent strong (80 to 100mph) gusts, but I will have to look at it in more detail when I have time.

EDIT: Here is the raw video from the side camera, pointing due north on Reuter Road about 1/3 mile east of S Evans Road: http://www.youtube.com/watch?v=58D8CmhhM1E

EDIT 2: The end of this video shows the window blow-out event from both front and rear cameras. Front camera faces due east, rear camera is due west: http://www.youtube.com/watch?v=em6Rlz5gL1Q

 

[Robert Edmonds]

Little gif animation I put together, combination of images from different people with me.

I think it gives a good sense of how it was obscured partially from our our location on 81, but if you watched closely you knew it was there.

 

[Mike Szentes]

Second chase i've done was the El Reno 5/31, link below of our footage, and it was remarkable. Sobering in knowledge of deaths and destruction. Next year out, i want to render assistance if possible. Anyone else do that regularly after a chase?

In the footage, i open and close with a lightning strike that shows the El Reno in it's F1-2 stage.

https://vimeo.com/68411998