Some Images of the Nocturnal “Casino Tornado”

On the evening of 21 Oct 2017, a short-lived and weak (EF1-rated) tornado struck the Riverwind Casino across the Canadian River from Norman, then crossed the wooded river bottoms before losing damaging ground circulation south of Highway 9 in southern Norman, between the river and a segment of Highway 9 that arches northwestward toward the Interstate. A low-slung funnel without damaging ground circulation (by definition, not a tornado anymore) persisted for a few minutes afterward, based on one link below and several other cellular-telephone images posted on social media. Please see the Public Information Statement from NWS Norman for more path details.

The tornado developed from a small storm-scale circulation that formed just behind the surface gust front of a quasi-linear convective system (QLCS), a.k.a. squall line. The parent circulation wrapped a hook echo of precipitation eastward while tightening a radar velocity couplet for a couple of volume scans. Squall-line tornadoes mostly are weak, small and short-lived, and this fit the mold.

Capturing this event on camera, even with mind-numbing mediocrity, was at least as much luck as skill. Before the circulation ever developed, I had driven a short distance to a hilltop near Highway 9 and 48th Avenue and set up my DSLR on a tripod facing west and northwest, simply with the intent of photographing the shelf cloud, hopefully accompanied by lightning. Those shelf photos turned out to be nothing too outstanding, and lightning was sparse and buried deep in cloud. Here is one shelf-cloud shot regardless, looking NW.

After hearing my phone buzz with the tornado warning, I readily spotted a small mesocyclone to the west with an embedded, pronounced, blocky cloud lowering, tucked behind the leading edge of the shelf cloud. Outdoor sirens quickly began wailing — remarkably fast response time on the city of Norman’s part, unlike 9 June 2012!

I adjusted some focal, f-stop, aperture, and ISO settings (I shoot all manual, all the time), and began firing away with 3-6-second “bulb” exposures. Though I didn’t recognize a for-sure tornado visually at that point, and somehow missed seeing the power flashes, I knew that sometimes the camera can bring out features with which the eye has more difficulty. Sure enough…

As it turns out, this was the tornado. It’s nothing that will win a juried Biennale competition or Pulitzer, nor even make a worthy piece of wallpaper, but it does document the event. Here is an annotated, contrast-enhanced version:

Given the positioning, this was a minute or two, at most, after it had hit the casino. My EXIF times turned out a few minutes too fast, due to clock drift since the last time I had adjusted my DSLR time in the spring. Adjusting for that drift places image time barely inside the known tornadic lifespan.

By coincidental good fortune for me, storm observer Brett Wright had set up shop on the OU campus, just northeast of the Gaylord journalism building (the domed structure in the shot below). He took a shot of the same cloud feature from a couple miles closer, looking SW, as its fuzzy tornadic vortex below produced one of the power flashes I didn’t see (probably due to camera setup seconds before). Here it Brett’s view at that time, used with permission.

Triangulating Brett’s position and viewing angle with mine matches the tornado track precisely. A minute and a half after my photo above, and on the front side of the remnant cloud-base feature, a tapered lowering appeared. This is much more obviously a condensation funnel than my skeptical eyes registered at the time, in the darkness.

Keep in mind this is a 4-5-second exposure, so the funnel is somewhat blurred. This contrast-enhanced version may help to reveal its shape better.

Some rain wrapped around the vortex from my perspective, temporarily blurring and obscuring the feature while others to its north got those fuzzy social-media photos of a fat cone funnel (such as this one from Classen Urgent Care near Classen and Highway 9, still 3 miles to my west). Whatever was left of the vortex died fast after that, as the gust front surged my direction, and cold outflow air undercut the entire process.

Skepticism: you see, I’m not like most storm observers. Instead of taking a “notches in the gun” approach and counting every maybe-nado, my attitude is closer to, “I used to live in Missouri, so you’ve got to show me!” Even after seeing video from the casino (which showed blowing debris but not a definitively closed circulation), I wasn’t certain I had been looking at a tornado until seeing posts about damage later, images of the funnel from others, and a zoomed view of my viewfinder at home. But there it was: the first QLCS tornado I’ve photographed at night (albeit poorly).

Unfortunately I did not think to screen-capture the radar display on my phone as it was happening, as I was merely glancing at it for situational awareness’ sake while concentrating on staring into the mess and shooting camera stills. Maybe I’ll post some radar shots here as an addendum eventually, after I get the chance to grab and process some archived Level-2 data.

Although this was “only” a weak tornado, it hit Riverwind Casino during a Beach Boys concert, highlighting a very difficult aspect of an issue about which I have been concerned for a very long time: large-venue preparedness for severe storms. Here is a 15-year-old conference paper on the topic, and much great work has been done since by professional large-venue and event societies to help facility managers and event organizers to prepare better.

When a tornado is non-supercellular (thereby giving little or no radar notice of its impending formation), and either develops on top of the venue or within a stone’s throw of it, warning lead time is practically impossible. Yet the area was in a tornado watch for over 5-1/2 hours, and smack in the middle of the greatest tornado probabilities in the severe-weather outlook issued at 1 a.m. the night before.

The idea is well-known in the weather-preparedness community that large venues and events should not wait for NWS warnings to act, due to the short (and sometimes zero) lead times — especially for quick-hit squall-line spinups like this. Fortunately this was weak as tornadoes go, and nobody was hurt or killed.


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