NWS released new information on Friday's tornado near El Reno OK, rating it EF5, and showing it to be a record width (2.6 miles). The map above shows the updated path, and the damage track from satellite (inset).
With the death toll now reaching 19 people, it was truly a dark and tragic day. I've been trying to make sense of what happened, and today's information along with a careful analysis of radar data offers some clues. The mesocyclone and tornado appeared to be "arcing" around a pivot point within the larger storm cell, and as it curved northeastward, it accelerated significantly. As some chasers have pointed out online, a simple analysis from conventional radar data of the movement of the storm-relative velocity couplet shows that the tornado, along with getting wider and more intense, increased it's forward speed from 20-25 mph to over 40 mph for a time (see speed annotations on the map above). This unanticipated movement may help explain why so many storm chasers were caught suddenly in the path, including the tragedy of Tim Samaras and his crew (see my prior post).
The map above also shows the location of 3 images that Shawna and I took while approaching the tornado and then moving south out of its way. The first image below shows the tornado in its early stages illuminated by lightning to our west-southwest:
This next image shows how hard it was to see the tornado at times, wrapped in rain curtains and poor contrast when it was about a mile to our west. This was truly frightening, and we high-tailed it to the south well out of its way.
This last image is from 2 miles south-southwest of the tornado when it was around 2 miles wide, looking like a large ghostly wall cloud on the ground:
I hope this tornado case forcibly reminds us that many tornadoes aren't always visible, and that they don't always move and behave the way we expect them to, even for the experts. Friday was a sad, scary day.
When I get time down the line, I'll try to post some more analysis about this case.
- Jon Davies 6/4/13
10 comments:
Hi Jon,
the cursory analysis looks pretty reasonable considering the difficulties involved. After seeing the picture of their vehicle the other day, I was wondering about the EF3 rating initially given, since it looked like EF4-5 would do. There was mention of an unusually strong RFD surge coinsiding with the sudden NErly turn of the vortex...with tragic results.
Dan Chaffee
Thanks for posting this. At the time we really could not understand what the storm was doing. Fortunately we were able to stay ahead of it, although it was close! I'm looking for a complete analysis of the day from you later.
Peggy and Mel
Jon, thanks for the update. I was actually in Adams Park just north and west of downtown El Reno. From our angle we could see it moving right to left of us (the southward arc). That arc easily could have saved my life and the dude I was with. We didn't have the best line of sight aas we were sheltered under a portico, surviving the baseball size hail (Never thought I'd be able to actually say baseball size hail). Then, I think all the cell phone towers got hit and we lost all data connectivity, so we had to sit where we were. I would have broken into the building had we seen it coming for us. I would have dealt with the consequences later.
2.6 mile wide. You just can't put your mind to one that big.
Thank you for this Jon. I am sure it was not easy writing it. -Kenny Allen
After my near-death experience with the rain-wrapped El Reno-Piedmont EF-5 in 2011 I decided to keep an extremely safe distance from last Friday's storm. My vantage point this time prevented me from getting any exciting footage but knowing what I know now about that storm I'm glad I erred on the side of safety and made several calculated retreats. NWS already had the warning out and the helicopters did there thing. I can only imagine what would have happened to spotters and chasers if this had occurred at night or if there had been more hills and trees.
Jon,
Did the increased speed and size at all correlate with what we were seeing on radar when the tornado occluded into the storm at just about that point? Would the occlusion have something to do with the increased speed and size and the RFD surge?
A truly scary and very sad day. I filmed the developing tornado from less than a mile to its south-east before bailing eastwards...the speed of the low clouds from a northerly quadrant behind the wall cloud was extraordinary, and must have been part of the massive RFD surge. I also timelapsed part of the earlier stages of the storm as a shower merged into it from the south...a roll cloud type feature was pushed out by this shower and was ingested into the main updraught...it was visibly rotating about its horizontal axis in a direction which would enhance SREH.
Jon, please do update this analysis and maybe do one on the Moore tornado if you get time...I learn so much from every single post storm analysis that include the skew-t and such, you're the first person that's been able to make it all make sense. I truly appreciate your extensive knowledge, ability, and willingness to teach others.
How's this for an eerie coincidence? Exactly one Gregorian calendar cycle passed between the tornado outbreaks of Friday, May 31, 1985 and Friday, May 31, 2013.
My photos were very similar Jon, dark under the storm, low contrast and poor visibility. Could only make out what must be the tor from heavy editing. See you at Chaser Con 2014. Will be a heavy session no doubt.
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