Chugwater Tornadic Supercell

August 10, 2010 by · 6 Comments
Filed under: Summary 

Chugwater WY, 20 Jun 10

SHORT: Observed tornado from second of two supercells E of Chugwater.

LONG: Since Scotts Bluff National Monument was just a few blocks from our motel doorstep, we had time for some late morning through midday hiking, as well as photographing wildflowers and other interesting scenery near the top, before grabbing a quick lunch and heading west to our target area of southeast WY. See, for us, the so-called “storm chase” vacation isn’t just about storms, but about appreciation of as much of the Great plains’ offerings of beauty and wonder, large and small, as possible — storms being the major component, but not the entire experience. And so it was that we strolled atop the bluff o’ tuff, pondering the view up this way from the Oregon Trail’s wagon trains rolling up the North Platte valley below, while also occasionally looking at surface maps and satellite images on our I-Phones, and considering the effect the stable air represented by this stratified overcast would have on the day’s convective potential.

Thin breaks and occasional peeks at the sun indicated some destabilization was occurring, in an area of nicely backed surface winds from there westward, and automated mesoanalyses of CAPE and CINH fields bore that hunch out. As we descended from the hill, as if on cue, the first towers began to erupt over the Laramie Range, where the clouds had been eroded over the highest terrain in the area, allowing maximum heating. We couldn’t see them through the stratus, of course, and I had doubts about how far E convection could make it off the mountains before getting into grunge and weakening There was no doubt we needed to follow Horace Greeley’s old advice and “go west”. As we did so, two storms started to rotate:

    1. A cell in the Wheatland/Dwyer area, headed NE toward Jay Em but also toward some decidedly stable air, and
    2. A storm moving somewhat more slowly and seemingly anchored along the foothills near Chugwater.

We went through Torrington along the way, then SW, catching a brief view of the distant and uninspiring base of the northern storm, before moving SW toward an area of obvious darkness above and beyond the intervening stratus deck. By the time we got to a good vantage W of Yoder and S of veteran WY, the southern storm, which had been a supercell, already was losing definition in its base and soon would turn into a strung-out, most likely elevated plume of convection.

Fortunately, the strong heating continued off the W edge of the stratus deck and the E edge of the mountains, firing additional convection still farther SW. With the boundary layer continuing to get more unstable in that direction, we backed through Yoder and S again past Hawk Springs. Then we then headed up the beautiful bluffs E of Chugwater along one of my favorite drives in the region (WY-313), only to greet an already well-developed and obviously surface-based storm by the time we arose on the high plateau E of I-25. The storm was calving off left splits, one of which can be seen beyond an abandoned farm structure in this shot looking WNW. Turning our attention to the WSW, the large, robust right mover quickly cut a clear slot and formed a broad, rotating, bowl-shaped lowering
behind it (and above the letter “s” ending my name in this wide-angle shot). This was only a few minutes after we had arrived at our location, and then, at 1624 MDT (2224 Z)…


You see, in most years, a tornado is such a rare and amazing event to witness for any storm observer. This year, I had experienced lousy luck with tornado photography in what has been a banner season for some others. In most cases (e.g., Bowdle SD, Faith SD, Campo CO), I wasn’t available to chase on the fantastic day in question. On one (10 May, OK), I (along with some other very talented chasers) got on the one storm that refused to produce anything more than a brief spinup while observable. On another (16 Jun, SD), the storm blocked the only safe road access to it with flooding and hooks filled with both precip and precip-wrapped tornadoes, while also going nuts on the other side.

After all that tornadic frustration, then, it surely felt good to see one that was not low-contrast, rain-wrapped and/or too brief to photograph, even if it was a small and otherwise not very newsworthy hose. The tornado slowly roamed wide-open land and, to our knowledge, hit no structures of consequence — just the way we like it. As seen from about 3-4 miles to its E, the tornado manifest initially as a tapering cone (zoom), with two episodes of visible ground contact. The first is shown in this zoom (see wide angle structure view), followed by a few minutes where neither condensation nor dust was evident under the base of the funnel (wide angle structure view), followed by a few minutes where full condensation planted again.

That vacillation was described by some observers as separating two tornadoes that occurred from the same vortex (by definition, a tornado must have ground contact), while others deemed it as one tornado with a weak interlude. What is a tornado? The ground was soaked out there, minimizing dust, although it did lose full-condensation again before lofting some combination of spray and dust (super wide, with storm structure). The tornado started to wrap deeply back into its occluding mesocyclone, then roped out.

Tornado-wise, that was all the storm could do. We felt fortunate to get there just in time! We also had to bail east, off the high plateau, because hailstones of 2 inches and larger in diameter started falling around us with discomforting splats and thuds right as I was shooting the last rope-out photo. We got out from under the vault with no hail impacts, then headed S and E in a very difficult effort to find a good W-NW view of the weakening supercell that wasn’t overly obstructed by terrain. Some others we know weren’t so lucky with hail. At that vantage, we encountered the Tempest bunch with Chuck, Chad Cowan, and Bill Reid, here shown calling for lodging from behind two giant hail craters patched with duct tape. Not far to our W, as the tornado began to narrow, that part of the vault immediately downshear from the low-level mesocyclone unceremoniously heaved forth gorilla hailstones up to 4 inches in diameter. It’s a good thing nobody was hurt by that hail (a vastly under-appreciated injury hazard in storm observing)!

The supercell moved over progressively more stable low-level air while attempting to backbuild, and eventually just died. That left us with no storm and some daylight, which we used for traveling to our motel in Sidney. On the way down toward I-90, we stopped to photograph an abandoned farm with soft stratocu and baby-blue sky in the background. We then hopped on the Interstate for a very unusual (for late June!) plunge through a late-afternoon regime of cool fog and mist, in the stratified air mass E of where the supercell had been.

Wyoming-Nebraska Tornadic Supercell

June 28, 2009 by · Comments Off on Wyoming-Nebraska Tornadic Supercell
Filed under: Summary, Uncategorized 

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!