May 31, 2013 El Reno Tornado

Apr 10, 2008
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Tulsa, OK
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I am working on some research for the 2013 El Reno tornado and have come across some interesting tidbits of data surrounding some of the specifics with regards to Twistex's fateful impact with the sub-vortex.

Several years ago while going through countless videos on YouTube I came across Jim Bishop's footage shot from I-40 where you see the headlights of Dan Robinson and Twistex as the powerful sub-vortex bears down on them. Their (Bishop's) view is cut off by the Radio Road overpass and once they re-establish their view of the tornado east of Radio Road, the tornado has morphed into a maxi wedge and neither Robinson's or Twistex's headlights are seen again.

Here is a link to the video:

I spent some time looking at the location on Google Earth and even visited the location on two separate occasions and can confirm that you can see vehicle headlights on Reuter Road from I-40 where the video was shot.

There was some speculation that perhaps the headlights were not of Robinson and Samaras, but were of Piotrowski and Marshall who were on Jensen. however, after reviewing both of their videos, the angles don't match up with the Bishop video.

More recently I found a Reddit thread where someone had done a few calculations from the Bishop video and came up with the same results:
https://www.reddit.com/r/tornado/comments/p2ck1p
Something I find interesting is most research papers and the general consensus is that Twistex was overtaken by the sub-vortex at roughly 23:23-23:24z (6:23-6:24pm) while the Jim Bishop video when compared to synced video found at: El Reno TED suggests Twistex was overtaken by the sub-vortex between 23:21:30-23:22:00z (6:21:30-6;22pm), or a full 1 to 2 minutes before what has been suggested in various research papers and official statements. I am curious if anyone has any thoughts on this.

Something else I found of interest is the evolution of the wall cloud/SVC (streamwise vorticity current) during the life cycle of the El Reno tornado. Initially, the El Reno tornado formed under a distinct wall cloud with a tail cloud/SVC extending to the north. During the first half of the tornado (west of HWY81), the tornado shifted southeast, away from the SVC, as the hook "uncoiled". A large precip core develop around the north side of the tornado and appeared to separate the tornado from the SVC as it approached HWY 81. Check out this incredible footage from Brenden Lindsey as he raced south to stay ahead of the tornado as it approached 81. He had a perfect view of this exact evolution.

Is it possible that the density current from this precip core, as it rotated cyclonically around the north, then west side of the tornado, shoved it east across HWY 81 causing it to accelerate?

East of HWY 81 the main sub-vortex began to turn left to the northeast and merged back into the wall cloud/SVC. The hook recoiled to the north. Perhaps the intense low-level updraft with the SVC acted like a giant vacuum and pulled the sub-vortex into it in a prolate cycloid looping motion. Twistex was under the SVC which is why they weren't experiencing any rain, and could be why Tim commented that they were in a bad spot.

Anyway, these are a few observations I have made from researching this tornado. Please share your thoughts and questions. I would love to get more discussion going about this tornado, especially with the 10 year anniversary coming up next year.
 
Aug 9, 2012
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Macomb, IL
stormoptics.smugmug.com
At around 3:43 in Brendon's video, I noticed what appeared to be a satellite tornado which got absorbed into the main circulation as it maxed out. Curious question, at one point do we consider it a "satellite tornado" versus being a sub-vortex of the entire tornado cyclone itself here (not at all questioning the science, I'm genuinely curious as these particular vortices looked very large compared to typical sub-vortices).

I don't have anything to base this off of, but I feel like some of the sub-vortexes on the El Reno, OK 31 May 2013 event could be considered satellite tornadoes of their own (similar to what occurred with the 04 May 2007 Greensburg, KS event)....versus a subvortex of the parent wedge tornado.

I ask this because I have seen other storms, where tornadoes have formed in the SVC or around the backside and then get absorbed into the main tornado...and this process continue to repeat itself. What makes this interesting to me is that dense precipitation curtain obscuring the view of the main circulation. Other storms that have shown this behavior (Pilger '14, DDC '16, Albert Lea '10, Dupree SD '10) have all been pretty visible or rain free.

I did not chase this particular event in OK but instead IL/MO near STL where I observe a wedge tornado, so I can't offer any personal insight into the situation itself in Central OK that day, except for the video I've seen on YT or here.

I don't know if he is on here, but Gene Moore has some excellent stills from the same area as Jim Bishop and Simon Brewer off the interstate where it maxed out to its full width. He has discussed his thoughts on Facebook about the tornado itself and has similar beliefs that some were actual satellite tornadoes versus sub-vortices. I will leave it at that though to avoid speaking for him more. However again, this is really just all hearsay as we can't say for 100% certainty. The atmosphere really knows no bounds and our human definitions of certain scientific events can be quite ambiguous and leave gray cracks for certain things.
 

Drew Terril

Staff member
It's not uncommon for tornadoes to accelerate as occlusion occurs, so that in and of itself isn't particularly noteworthy. Had it been a mile wide or an otherwise more "normal" size for a wedge, I'm not sure we would consider it all that out of the ordinary. Granted, that's my opinion, and I'm sure others will think differently, but that's my thinking as someone who's been chasing since the mid 2000s, and was following weather for a good decade before that.

To Ethan's question about sub-vortex vs satellite tornado, I really think it boils down to whether it's within, or outside, of the boundaries of what we're deeming the parent tornado to be. As far as the HP nature of the storm vs others showing a similar behavior, I think that really boils down to moisture aloft (or lack thereof) and the discrete nature of days like Pilger, vs El Reno looking more like a tail end charlie. It's been long enough since I've looked at upper air maps that I don't remember what the upper levels looked like on those days, but I suspect Pilger had stronger flow in the 500-700 range to facilitate venting. I doubt that DDC had dews nearly as high as El Reno or Pilger, but without looking at the data, I'm guessing both DDC and Pilger had at least some dry air aloft as well. Pilger almost certainly as it was a very discrete storm. From what I recall about El Reno (I did not chase that day as I was on duty with my Reserve unit), there was very little capping and a ton of forcing due to the surface low, whereas (if memory serves) DDC and Pilger utilized boundaries from morning convection as their forcing mechanism, which was much more subtle than the surface low that El Reno had to work with.
 
Aug 9, 2012
548
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Macomb, IL
stormoptics.smugmug.com
I found another video that might help illuminate this situation a bit, one that I had not viewed before. From 9:12 onward it gets pretty interesting. You can see how fast the tornado goes from multiple vortex to wedge and then breaks down again into multiple vortices before a huge dense curtain of precipitation obscures most of the tornado cyclone. Around 11:55 mark, you can see the tornado re-emerge again from that dense precipitation core as a large wedge with rotating vortices around it. It then appears to get cloaked in heavy precipitation again and then is visualized again toward the end as the giant wedge with subvortices similar to Skip Talbot's video. The vortices on the outer edge are interesting to me. I'm just assuming it is because as noted above by Drew, that it could be the high RH value of the inflow parcels to the storm making every wisp of vorticity visible to the naked eye. I seem to remember observations that day running with temps in the mid-upper 80s and dews in the upper 70s in that localized area W of OKC with high CAPE/shear leading to a maxed out STP.

Another added note: It appears the storm chaser here is positioned in the RFD portion of the storm just to the W of the tornado. This would typically be a risky manuevur, but looking at the track of this particular tornado, it actually may have been a safer position than in clear air to the S or E of the storm given its dramatic shift in track. Just an observation though. I don't think one should take this as gospel though as other storms anchored on boundaries with high CAPE/shear combinations have swung back west or moved slowly that they retrograded westward (Bennington '13, Coleridge '14 examples).

Here is the video:
 
Apr 10, 2008
509
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Tulsa, OK
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Each of the sub-vorticies of the El Reno were exactly that, sub-vorticies and not satellite tornadoes. Only one satellite tornado occurred, and that was an anti-cyclonic tornado southeast of the main tornado. Each one of the sub-vorticies of the El Reno tornado formed within the MVMC (multi-vortex mesocyclone) and were just part of the SVC process. In this case, the extreme environmental conditions created an exceptionally large MVMC that was very efficient at creating intermittent "parades of vorticies" that exhibited abnormally large sub-vorticies.

I can see how it would be confusing, even when watching the video. The sub-vortex which impacted the Twistex team was particularly exceptional in size and duration. I argue that the behavior/evolution of the El Reno tornado was more erratic and unpredictable than most tornadoes, although not unprecedented by any means.