2010 Chase Season Dénouement

August 14, 2010 by · 1 Comment
Filed under: Summary 

22 Jun 2010
Southeast WY to North Platte NEb

SHORT: Outflow-dominant supercell observed twice — once in SE WY and another in NEb Panhandle. Gorgeous sunset supercell S of Paxton NEb.

LONG: We were hoping for one final photogenic supercell for our chase vacation, and instead got two.

A piping hot lunch at a local cafe in downtown Sidney NEb, featuring a platter of smashed and fried Rocky Mountain oysters, settled down hunger’s restlessness just long enough for us to watch satellite imagery on the mobile phone, seeking first signs of convective initiation on the Laramie Range to our W. This area would experience favorable upslope flow, decent low-level shear and deep-layer winds, along with sustained surface heating in the absence of any appreciable, antecedent cloud cover, but moisture seemed a tad on the scant side. Once the first towers started to fire NW of CYS, we hopped onto I-80 and roared westward.

By the time we got to Pine Bluffs WY, deep towers were visible with glaciation to our NW. We could see the cloud bases easily, so we fueled at a truck stop there as I chugged down a cold, delicious A&W float. I also reserved a room in LBF for the night using a combination of forecast storm motion and positioning needed to go back home the next day, while watching for a storm to congeal and organize from the agitated area. Soon, it did, and we took off W through Burns and then N, retracing in reverse a segment of our chase path from the tornadic Chugwater event two days prior.

True to the lack of more robust moisture, the bases seemed uncomfortably high, and I was troubled further by how fast the cells started moving E off the mountains as we approached. Was the convection already spewing outflow? Yes! We barely beat the storm to the intersection of WY-213 and WY-216 W of Albin, near which I shot this photo looking W. Yes, there were updraft bases all right, but they were being undercut very quickly by wickedly cold currents hurtling SE from the precip cores. We headed E on 216 to Albin, having to make a decision there either to:

    1. Take unpaved back roads and stay closer to an outflow-surfing wind and ice machine, risking its outrunning us for good somewhere not far E of the WY-NEb border, or

    2. Shoot back down to I-90 and bust eastward at higher legal speeds so we could stay abeam and eventually get back ahead of the storm on a north road.

Although I’ve seldom seen such an outflow-dominant storm recover to produce tornadoes, it has happened on one occasion. Furthermore, such storms can produce interesting and sometimes beautiful cloud formations, especially out on the high plains. The decision was easy.

Meanwhile, before zooming down to the Interstate, we watched the storm cross the road to our N, spying a suspicious-looking but very short-lived formation buried in a mesocyclonic notch region (enhanced crop-n-zoom of previous image). That feature quickly vanished, and the whole messy and wild-looking process roared past.

By the time we got just the few miles S to I-80, the storm already had gotten well off to the NE, brilliantly festooning a deep blue sky (wide-angle view from I-90 near the border), with a high and ragged base visible on the trailing flank. That, along with the main updraft base of the storm to our left, were visible as we cruised E to Sidney, then N toward Gurley — in the process retracing a late-day segment of our trek from the previous season’s intercept of the LaGrange WY supercell. For our nearly continuous view of the updraft while driving, and several chasers who were closer at that time and didn’t see any tornado, I had to question the “sheriffnado” reports just E of the border in NEb.

We got directly ahead of the storm again E of Gurley, watching its somewhat-lower base with a small, shallow wall cloud developing to our WNW (wide-angle view) while a deck of low clouds formed overhead. The storm itself was decelerating markedly, and its own outflow boundary appeared to outrun its main reflectivity area (and mesocyclone aloft). I got a dread that the supercell wouldn’t last much longer; and it certainly did not. A zoom view shows the wall cloud that was surrounded by translucent precip. Within minutes, a fuzzy gray bowl of precip appeared right in and under the wall cloud, descending and expanding and obliterating the wall cloud as it reached the ground, and making a splendid example of a tornado look-alike.

Was this a descending reflectivity core (DRC) that came down in a very deleterious place for any low-level mesocyclone’s development and survival? It sure seemed as such. Here’s the view 3 minutes later, when the precip core further expanded and utterly obliterated the cloud base where the wall cloud previously had dangled. Within 11 minutes more, the outflow had gone past, the low clouds cleared away to reveal an astonishingly rapid storm demise!

Thinking that was it for our chase season, we headed E toward LBF, only to see a stunning and spectacular convective eruption to our SE, S of Paxton, beneath a waxing gibbous moon and shortly before sunset. As this storm evolved into a short-lived supercell, we admired the amazing spectacle from a corn field a couple of miles S of the Interstate, until an inverse relationship between amount of sunlight and mosquitoes hastened our resumption of the trip. What a wonderful way to close out the last chase of Spring 2010!

When we settled into our room in LBF, the clerk remembered my call and said we were smart to do what we did many hours before; all the rooms in LBF were booked up solid! After 11 p.m., we noticed a dramatic increase in lightning to our N-W, as storms erupted along the outflow boundary. While cruising S of town in search of a good vantage in that direction, the storms weakened again, precluding any decent lightning photo opportunities, though we did salvage a nice look at lunar crepusculars around an altocumulus deck.

This was a rewarding day, one that left us in ideal geographic position to do something we had wanted for a long time: pick up a stone fencepost from one of the quarries near RSL. It would be right along the way home the following day. Our adventure in doing so was a marvelous glimpse of Americana, chronicled in more detail in this BLOG entry. The d̩nouement had been written on our chase season Рone that was, at times, agonizingly frustrating, and at others, as fulfilling as can be. What adventures await in 2011?

Fun with Small Nebraska Panhandle Supercells

July 14, 2010 by · Comments Off on Fun with Small Nebraska Panhandle Supercells
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Harrison-Gering NE, 19 Jun 10

SHORT: Intercepted 3 nontornadic supercells in Nebraska Panhandle, one after dark near BFF.

LONG: A cold front had swept out of the Dakotas following our last storm intercept day. That stabilized the air mass for awhile and gave a couple of non-chase days for laundry, sightseeing, relaxed travel SW toward an eventual central High Plains target area, and photographing abandoned buildings of various kinds over the Dakotas and western Nebraska: an old schoolhouse, a long-disused, small-town rail station,a barn, the back door of another barn, a mostly intact farmhouse, and a gradually collapsing old house looking in and from without. Elke and I hadn’t been back in the Dakotas for a few years; and while storms beckoned us away, it was great to see the northern Plains again, especially in such a verdant, moist state.

The front’s trailing remnants stalled across the central High Plains beneath favorable mid-upper flow for supercells, while easterly and southeasterly flow to its N would yield decent low-level hodographs. A textbook, multi-day, central Great Plains upslope pattern was setting up, and we had time to participate before the chase season closed out. The main concern on this day was a lack of more robust moisture, but I wasn’t concerned much about whether we would see a storm form, given favorable upslope flow into the higher terrain of eastern Wyoming. We left PIR by mid-morning, targeting the Wyoming/Nebraska border region, with a short venture into the whimsical (but fun) tourist trap of Wall Drug.

As we left Wall Drug, convective towers bubbled over the Black Hills, but struggled amidst the lack of moisture. Moist advection started to solve that problem by the time we got down to around Harrison NE, with a discrete storm erupting to our SW over eastern WY and a short line of some overshooting cells to our NW (closeness exaggerated in the zoom view) across northeast WY, W of the Black Hills. Although both eventually would yield supercells, we went for the cleaner, more moist target to the SW.

We found a one-lane dirt road between Agate Fossil Beds and Mitchell, off NE-29 — no crowds, no traffic, nothing but us, a vast rolling prairie, a storm organizing into a slowly moving LP supercell, and dozens of different bird species joyously singing across the mild breezes.

The chase season to date, and the vacation in particular, had featured lots of driving and moderately- to fast-moving storms. This was a most welcome relief! We stayed there for nearly an hour, just enjoying the peace and solitude, punctuated only with an occasional rumble of thunder from the small, high-based supercell. It didn’t matter at all that this storm likely could never produce a tornado. The soothing salve of the Great Plains in springtime worked its rejuvenating magic on us, and we experienced the most pure, relaxing enjoyment in the face of a storm all season so far. It was a deep-tissue massage for the soul, a reconnection with why we’re out there to begin with.

I also, finally, had a chance to set up our new HD video camera on a tripod, and let it stand there and roll (our first video shooting in several years). [I eventually will construct some time lapses from this footage.] We had received this as a gift shortly before leaving on our trip, and I hadn’t really had a chance to learn how to use it right, amidst all the more active chasing we had done so far. The main intent of this video camera will be to shoot HD time lapses for our own enjoyment and perhaps uploading online; but first priority will be still photography. In this case, our video will feature a chorus of birds in stereo, the breeze, and an approaching storm.

As the first supercell grew more feeble, another small storm erupted very nearby to its S (and our SW), upon which I re-aimed the video and still cameras. This wide-angle shot shows both cumulonimbi at once, and illustrates how neighborly they were. It’s as if one was asking the other, “Would you like to come in and sit a spell? I’ve made some fresh lllllll-lemonade!” (quote [tm] Ryan Jewell). Instead, the northern storm shriveled to vaporous oblivion, leaving the southern one to spin along for a little while NW-N of Mitchell (and by the time of this shot, SSW of us). We finally decided to head S before the storm crossed NE-29, reserving a motel in the BFF suburb of Gering (which wasn’t easy due to all the hail-claim adjusters in town), packing the tripods, and beating the thin hail core across the road. This second supercell soon raised its base and weakened (view looking NE from a few miles E of Mitchell). It was time for some supper in nearby BFF.

As we dined, convection began popping up all around, almost at random, as if a pleasurable rash. Most of it was weak and inconsequential. One storm, however, took good root and became dominant to our WSW. We had some trouble finding the place of lodging we had reserved in Gering (in a neighborhood just W of downtown, but also just a few blocks from the entrance to Scotts Bluff National Monument, as it turned out to our good fortune). After we checked in, we headed over the hill S of the bluff to watch the now-weakening storm move in from the W. Its lightning slowed down dramatically as we set up tripods (of course), but not before one spectacular spark sliced through the twilight sky beneath for sloping base of the forward-flank anvil area. We also enjoyed seeing the apparently dying supercell’s remains float overhead beneath the moonlight, then headed back to our room.

While we were inside, unpacking and unwinding, I noticed lightning activity picking up outside. Another storm? No…after we gave up on it, the supercell rejuvenated and drifted just to our N over BFF, sparking anew from within! Out the door and right back up the hill we went, this time on its E side, to watch the spectacle. Once again, as we got set up, it weakened, but not before producing some nice intracloud flashes around a moonlit main updraft tower that was drying up from below.

I didn’t think to bring the new camcorder back out, and hadn’t yet tried the video functions of the 5DM2 still camera. So, instead, here’s a poor-man’s time lapse I constructed of still photos of the weakening storm moving away from BFF, where it had dumped hail up to baseball size. More work for those hotel-hogging insurance adjusters!