Wyoming-Nebraska Tornadic Supercell

June 28, 2009 by · Comments Off on Wyoming-Nebraska Tornadic Supercell
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5 Jun 9, Bushnell to Gurley NEb

SHORT: Intercepted mature supercell with tornado in progress in SErn Goshen County WY, looking NW from N of Bushnell NE. Spectacular rope-out followed by several structure photography stops over the course of a few hours, before landing in OGA for the night.

LONG: We began the day in HYS after driving up from Norman the day before, when I had no sleep all night the 3rd or all day the 4th. We slept in at HYS as a result…maybe a little too long. The target area was fairly well focused — the CYS Ridge region and any convection that might erupt off the southern LAR range. Unfortunately for us, the farthest possible zone within the target area was where it erupted, but we managed to salvage the day anyway.

Flat “pancakus” Cu hovered over the CYS ridge to our N as we approached Wray CO, with dense cirrus overhead limiting heating. Meanwhile some small echoes began to appear near the LAR range NW of CYS. After a quick service stop in Holyoke, one of those echoes (the eventual La Grange WY storm) was starting to get a compact and intense core, with no apparent sources of convective interference to its S,either in VIS or reflectivity imagery. Off we torn. By now the storm was starting to look supercellular on radar, and we had to haul west on I-80.

Once we got past SNY, a darkened, elongated smudge appeared under the cirrus deck to our WNW, and tornado warnings began. Keith had called DF to let him know that the storm was about to produce, and we made good time along the Interstate toward the WY border. We turned N through Bushnell onto a road that DeLorme indicated was paved…but it became gravel and hard-packed dirt.

About 2-3 N of Bushnell and barely E of the WY border, we began to see the tornado on the SW edge of a broad wall cloud — a nearly vertical stovepipe with some precip and/or dust around the condensation funnel. By the time we found a good vantage a few minutes later — a hillside ~5 N of Bushnell, the tornado began to narrow into a tapered, curved cone. By the time I pulled over, got out, ran to the other side of the road and hoisted the camera, it already was in transition through elephant-trunk (wide-angle and with zoom lens) to rope stage, at the S edge of a gigantic, ragged wall cloud.

This was Emily’s very first tornado, which earned her a vigorous high-5 from me. It also was Elke’s third birthday tornado, a most fitting atmospheric present for her. Finally, this was the second time that Elke, DF and I had seen a tornado in one state from a different state (the other being in Montana but seen from North Dakota on 6 Jun 5, the infamous “Ekalaka Smacka Backa” chase). We admired and photographed the narrowing then roping tube from a distance, watching the sinewy condensation funnel rope out in a spectacular arc, then finally split into segments and die quickly. We had seen a little under half of its lifetime, based on others’ accounts. After the long and pounding haul from HYS, we felt very fortunate to see even the last 7-8 minutes of its lifetime.

We then headed E on some unmarked, mainly gravel roads, eventually meeting up with some folks including Hodo, MattC, Rocky, Charles, Alnado, and a few others who had the privelege of witnessing the tornado from closer and/or longer time. We also had the pleasure of talking with Dave Hoadley, who saw the last few minutes of the tornado from even farther away, N of Kimball. Gotta love that long High Plains visibility!

After it paid the tornado troll’s toll for entry into Nebraska, the supercell as a whole became somewhat ragged, but still well-defined and visually pleasing. A couple of occlusions along the way E yielded moderately rotating wall clouds — one extruding a conical cloud lowering that spun slowly, as if trying to tighten into a funnel. Another lowering later, NNW of Kimball, briefly stretched into a ragged but definitely rotating funnel with no apparent debris beneath, way back in an old occlusion to the NNW (looking N under newer wall cloud).

We then got road-screwed and had to drop S to I-80, whereupon we bid farewell to DF and Emily (who had to fly out of ICT early the next morning), then headed back N out of SNY to watch the storm some more.

By the time we got back on it, near and E of Gurley, the supercell had acquired a messy underbelly with a ground-scraping wall cloud, beneath a highly tilted convective plume, and fronted by a skirt of striated cloud material. The storm cast a long, sharp shadow to the ESE while spinning over the beautifully verdant wheat fields of southwest Nebraska, and later, posing before a deployed sticknet.

Soon it was getting dark, so we went SE to OGA for the night, whereupon we got fast-food dinner and a motel room, then began hearing reports of nighttime tornadoes from “our storm”, headed right for OGA! We bailed S of town a few miles to spot. A new, tornado-warned supercell to our E took over and sent a raging pool of outflow toward us, killing the long-lived LaGrange-Gurley supercell at last.

We worked hard for everything we saw on this first chase day of the vacation, and slept well that night, bathed in gratitude and satisfaction for a pretty tornado and some grand displays of supercell formations along the way. What a fantastic way to start a grand June 2009 storm-observing odyssey across the Great Plains!