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?

Ice Machine in Yuma, Colorado

August 13, 2010 by · 1 Comment
Filed under: Summary 

Yuma CO, 21 Jun 10

SHORT: Observed 3 supercells ultimately merge into one over Yuma CO — damaging hail, beautiful post-storm skies.

LONG:Join us on this fine, toasty day for a tale of three supercells that became one, the hellish hailstorm that resulted, and a storm-observing couple who chased them.

Elke and I began the day in Sidney with a target area of NE Colorado, in the region of relatively backed low-level flow. We were uncertain whether the storm(s) of interest would fire on the Front Range or on a convergence boundary farther E, in somewhat more moist air SW of Sterling. The answer: yes, and yes! From Sterling, we observed the growing anvil from a storm near DEN that was high-based but starting to rotate aloft (based on radar velocity imagery), along with multiple towers bubbling just to our SW, beneath and S of the anvil canopy.

The tower at left, in the last shot, erupted into a pre-supercellular supercell, before anvil shadowing had a chance to mitigate diabatic heating of its immediate inflow layer. We dropped S to stay ahead of both this storm and the more distant and growing beast roaring out of DEN. Even in this early stage, the new storm displayed nice corkscrewing action (the base of the DEN storm becoming visible at distant rear), looking W from the N side of the Colorado Plains Regional Airport (AKO). The storm spun around for a short while, moving slowly closer to us without growing a very large updraft. Meanwhile the DEN storm churned along essentially straight toward us, with a wall cloud and lowering becoming faintly visible in the distance under its southern flank. I sensed this closer storm wasn’t long for the world.

We headed E through Yuma, taking note of potential hail shelters for four reasons:

    1. The combination of the big western storm and any merger with a foregoing supercell could spawn some healthy ice bombs,
    2. I still had a good windshield and didn’t want to bash the hell out of my new vehicle with gorilla hail this soon,
    3. We deemed it wise to plan sheltering options in case we didn’t have time to bail S of Yuma and ahead of any storm acceleration, and
    4. The next major town to the E was Wray, its S escape option (US-385) known to be under heavy construction with a surely nerve-wracking and possibly vehicle-destroying situation of one-lane, pilot-car closure for many miles!

Meanwhile, another tower went up in some slightly more strongly heated air several miles farther S (to our SW), also evolving into a skinny supercell rather quickly, and likewise coming under the sprawling and thickening anvil of the onrushing western storm. In the last shot, from just E of Yuma, the outflow-surfing updraft base of the massive western menace is visible at distant left, and its downshear anvil canopy distant right — dwarfing the nearer but much smaller supercellular plume. The older tower (spinning down to its N) eventually merged with the northern part of the newer, closer supercell as the latter expanded. Then it expanded further and assumed some sharply sculpted structure, moving slowly E and expanding its updraft still further.

One thing it did do, before being absorbed by the big bad brute impending, was glow forth an eerie, ghostly layering of light and shadow, interspersed with subtle pastel hues, a weird sight that I’ve seldom seen to this extreme. Back under its SW flank, the near storm developed a circular, slowly rotating, mottled texture to its main updraft region, and even sported a ragged, conical lowering for a short time. What could this storm have done with an extra hour or two before being swallowed by the expanding, ever-intensifying convective Pac-Man stampeding eastward toward us…and it?

The western storm charged onward, turning more deviantly rightward such that its main mesocyclone region — now an HP “stormzilla” with suspicious lowerings in its “notch” area (actual view and deeply enhanced zoom) would go just S of Yuma — while the value or near-forward flank region would absorb our nearby supercell virtually overhead. A short-lived lowering that preceded those photos raised a tight little plume of dust, but due to distance and poor contrast, we’re unsure if it was tornadic.

Though expected, this event still lit a sense of foreboding within, as if billions of icy little swords of Damocles dangled high above. This merging maelstrom of mayhem accelerated too, sure to turn into a destructive tempest of a nastiness and ugliness that we cared not to endure unsheltered. Time to get into town and under that covering!

Surprisingly, we scooted under the canopy of an abandoned drive-in restaurant after only one other car: the county sheriff. Only once the hail began did other vehicles seek room there — most in utter futility. Much as when it was the place to go in Yuma for icy treats of another kind…first-come, first-served! Within ten minutes, hail up to 2 inches in diameter started hammering away on the tin roof, becoming dense in coverage and ear-splitting in loudness. Vehicles that couldn’t fit got a glass-busting, steel-denting beatdown.

Although we had been hailed on while in a vehicle on several occasions, Elke and I hadn’t yet experienced a rip-roaring hailstorm together from under outdoor shelter. It was quality time as a married couple — at least, once I stopped yelling over the deafening din about the camera lens I couldn’t find. We had a blast.

I actually remembered to shoot some video of this with our new HD camcorder (video being something I’m not accustomed to doing after several years without), while also firing off a few hi-res DSLR stills with the lens that turned out to be in my left hand the whole time prior. One of those stills captured the a rare, split-second scene indeed: a hailstone exploding upon striking the pavement. It reminds me of some artist’s conception of an asteroid striking the moon, minus the fireball in the locus of impact.

After the beating was over, we secured a room at a little yellow motel. The lady who ran the motel mentioned that her daughter owned a restaurant and bar in town, Main Event, that was open and serving dinner late. Outstanding…we could avoid the usual storm observer’s conflict between getting dinner before early, small-town closing times and heading out for photography!

We headed a few miles SE of town to examine field hail and photograph the beautiful late-day, post-storm light (looking NE and looking WNW). Here are a few nice examples of that hail, about 45 minutes after it fell (culled from grassy, protected areas):

  1. Variably opaque core, clear outer layer with numerous radial bubbles
  2. Same stone silhouetted against the sky to illustrate its translucence
  3. Different stone, larger opaque core
  4. Two hailstones: Entirely opaque and rounded, the other asymmetric, broken and of mixed opacity
  5. Right before the sun sets, four hailstones on a gravel road [Would this compel Lucinda Williams to re-title one of her best-selling songs accordingly?]

While looking down at the hail, don’t forget to look overhead! Upon doing so, we saw sunset-lit fractocumuli shedding condensation vortices, including this ragged funnel and a separate, fishhook-shaped horseshoe vortex that wandered off to the E, slowly spinning down on its own for many minutes in the warming colors of the late-day rays (zoom). Here’s the western sky at the time.

All manner of fascinating processes were happening. Off to the SE rose a skinny, tilted tower, elevated atop the shallow stable layer from the earlier storms, seemed to be divided into two stepwise manifestations of the same convective plumes — one rooted just above the boundary layer, and a second slanted along some higher surface, with a backshear on the W side of the upper layer. Meanwhile, off to our E, dark wisps of scud passed placidly in front of a gorgeously glowing tower in the back side of the MCS. All of this while immersed in the luxuriantly earthy scent of rain-soaked farmland, while western meadowlarks sang from all sides…

We were getting hungry, though; so we cruised back into town for what turned out to be a very good meal at Main Event. I recommend the place for a late dinner if you end up anywhere near Yuma after a chase.

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.

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