Supercell Four Play

December 30, 2012 by · Comments Off on Supercell Four Play
Filed under: Summary 

Northeast South Dakota
17 Jun 12

SHORT: Very enjoyable chase day. Saw 4 supercells, each photogenic in its own way, each with its own distinctive personality.

Two days prior, Matt Crowther had accompanied us for a pleasant storm-photography jaunt across western SD, followed by a wonderful day in the Badlands, and then…this fantastic end to the storm-intercept parts of our vacations. Truly, it was a tale of four supercells.

Prediction and Positioning
Multiple days of large convective volumes over the southern Plains had left the trajectories feeding northern Plains systems rather moisture deprived. This was the first day in many where we would get at least a narrow plume of at least marginally favorable moisture for robust supercells, beneath strong flow aloft that was likely to be aligned nearly orthogonal to the main frontal zone. Strong capping farther south limited the prospective action to a chunk of land covering mainly northeast SD, perhaps creeping slightly into MN before dark.

Targeting that area from a start in PIR, we headed N and E toward a general storm-initiation prediction of ABR. Along the way, we stopped to photograph a pretty cirrus scene above one of the glacial lakes, along with a couple of farmsteads abandoned to cryptically artistic decay as well as to the risen waters of a natural lake.

After fueling in Ipswich, the heading N several miles, we noticed two areas of deepening cumuli and occasional fatter towers:
1. To our SW, generally in an elliptical area corresponding to the slow-moving frontal zone, and
2. To our ESE-S-SSW, along a differential-heating zone rendered by the S edge of a persistent mid-upper level cloud deck.

Both regimes were in the target zone, so we zigzagged back toward the N side of ABR as towers kept deepening. Finally, as we got back under the old differential-heating zone, several storms went up basically at once, in several directions. The “cleanest”, most promising-looking, and least impeded by neighboring activity was a cell to our WSW, W of ABR. It offered tumultuous tidings to that fair city should it turn rightward.

Aberdeen Supercell
The storm aiming for ABR seemed in optimal positioning–near the union of the two initiation regimes, and well-located with respect to potentially rightward-deviant motion directly along the differential-heating boundary (and any vorticity generated thereon). As seen looking W from just N of the WFO (which is on the N side of town), the new storm quickly assumed visual supercellular characteristics, then moved in our general direction. A more newly formed, upstream cell was casting some of its own downshear precip into the flank of the supercell, making it somewhat messy and HP in character.

As the forward-flank and vault regions began looming overhead, we headed S and E out of ABR to avoid dealing with town traffic in heavy rain and hail. E of ABR, we stopped to look back toward the storm, now sporting a well-developed wall cloud that was weakly rotating; meanwhile, large-hail reports became part of radio chatter from the area under the storm.

Pacing the storm eastward on US-12, in stepwise fashion, we noticed that the mesocyclone region experienced a disorganizing phase, then reorganized into a beautifully striated stack. The storm still was plagued by a bit too much precip, and ultimately paid the price by gusting out near Groton. This would have made a fine and worthwhile chase day anyway!

Peever HP Supercell
Keeping ahead of the self-destructive ABR storm, we mulled our options, increasingly confident that we could use US-12 as a vector to outflank a dark, murky storm above the ENE horizon that radar indicated to be a large, HP supercell. Why not? There still was plenty of daylight and an abiding curiosity in what the other side looked like. We’re so glad we did!

By the time we outpaced this supercell near I-29, it storm was tornado-warned, with a major mesocyclone evident in velocity imagery, but a dark and dense-looking wrap-around core apparent visually. We wanted no part of a bear’s-cage penetration of this somewhat fast-moving storm, so we stayed back to observe and photograph its striated, menacingly elegant cloud forms. Here’s the other side looking WNW, as seen from just E of I-29 near Summit, and looking N toward the area near Peever, as seen from between Marvin and Milbank. In the last shot, the curvature of the farm road nearly mirrored that of the supercell, lending a fortuitous and much-appreciated composition.

The storm’s structure became more fuzzy and outflow-dominant after that, while precip from still more storms forming to our SW began to fall. We headed S out of Milbank to clear as much of that precip as possible, concerned for the future of any new storms due to
1. The outflow surge from the big complex gathering to our N, and
2. Impending sunset with related loss of insolation-driven surface diabatic heating.

First Clear Lake Supercell
Storms to our SW didn’t look too impressive on radar, and were hard to see due to intervening precip. At that point, Matt and we agreed to split up, since he had to be back in ATL in another couple days, and we seemed done for the day.

The atmosphere had other plans. Though out of ready range of communication via hand-held portable radios, we independently headed S of Goodwin and W of Clear Lake, staying reasonably close as one of the southwestern storms took on a supercellular appearance, its base getting more circular and striated with each passing minute. The brief wall cloud in the last shot went away, however, and the storm became somewhat higher-based as it moved to our N.

Obviously destined to be nontornadic, the supercell nonetheless put on one final, fantastic show of structure, leaving us thoroughly bedazzled (and once again wishing a specific and exceptionally deep appreciator of such atmospheric beauty–the great Al Moller–could be there to see it!). This storm, beautifully sculpted as it was, always seemed to be sucking too much of its own forward-flank outflow. Finally, it couldn’t take any more low-theta-e abuse, and quickly became elevated and weakened.

Second Clear Lake Supercell
As we watched the first supercell shrivel and wane…lo! What had we here?

Along came another. A somewhat distant and previously unimpressive-looking final storm got organized rather quickly in the sunset light, sporting a variably ragged wall cloud and obvious storm-scale rotation, while merrily ingesting a plume of warm-advection recovery air behind the prior storm.

We felt the inflow get warmer as the final supercell drew nearer, then moved abeam to our N, offering a spectacular scene of a striated storm spraying red rain. Without dense precip to obscure our view of this classic supercell’s base, we remained in place and let the storm move to our NE, its newly reorganized wall-cloud region nearly ground-scraping at times, albeit with only slow rotation of the low-scud. Tufts of color tickled protrusions from the storm’s base as an RFD cut around the near (back) side, and a clear slot matured. This was about as close as the storm ever came to producing a tornado, but even the tightest rotation never was very intense visually.

Zigzagging generally eastward, we dropped to the edge of the Coteau des Prairies escarpment and then let the increasingly disorganized supercell go. The messy storm receded eastward into both MN and the deepening twilight, a fading and cloud-filtered alpenglow from high above casting subtle pastels across the landscape. We appreciated a brief splash of post-sunset color in the northwestern sky, then headed into ATY for the night.

Any one of these splendid storms, on its own merit, would have justified a green stamp of success on this storm-observing day. We were blessed with all four of them–essentially, four chase days in one! This was a good thing, for it turned out to be the last of the trip. A casual, three-day drive south to home (with side excursions for sightseeing) would follow, ending the Edwards’ 2012 Great Plains sojourn. Those would be our last supercells seen until one autumn storm on the way to a Colorado vacation.

Over the Belle Fourche River

December 23, 2012 by · 1 Comment
Filed under: Summary 

Elm Springs SD
15 Jun 12

SHORT: Another rewarding day considering low expectations. High-based but high-contrast and scenic storms over scenic High Plains of western SD.


The prior day, Matt Crowther and we had enjoyed a nonconvective hiking and driving adventure at Devils Tower, staying in Hulett, WY. Highly recommended: the airport/golf-course restaurant at Hulett, which is on a plateau overlooking the town and Devils Tower…great steaks and (according to Matt and Elke anyway) good beer and wine too. On this day, Elke and I did laundry in Belle Fourche while Matt dealt with some car maintenance, then we met at a high spot overlooking Belle Fourche Reservoir to watch for convective initiation.

Moisture was progged to be modest and analyzed to be downright meager. A series of MCSs over the southern High Plains during the previous few days had precluded ample return of rich boundary-layer moisture to these regions, though low-level storm-relative inflow and marginal shear were likely just to the E of a north-south trough near the SD-WY border. Our supercellular expectations duly tempered, we were content to see any sort of photogenic convection on this day, over such a beautiful landscape as the western SD plains.

While manning our convective sentry near the lake, deep towers began to develop over and immediately NE of an apparent source of lift located very near the northeast fringe of the Black Hills. The convergence zone associated with the trough appeared to shift E somewhat and intersect an area where heating of higher terrain was aiding in a sort of chimney effect for turrets tilting downshear. We zigzagged E and S past Nisland and Vale, stopping a couple times along the way to photograph the resulting young Cb that erupted into the deep blue Dakota sky–here with an abandoned shack and Bear Butte in the foreground to our SE, and here a couple minutes later with “just” the wide-open short-grass prairie. We headed S toward Bear Butte, stopping at an abandoned, antique pickup that Elke and I noticed ten years prior. I long had wanted to photograph that truck with an interesting sky in the background, and this was the welcomed result!

Navigating around Bear Butte, we took a winding, generally ENE course along SD-34 and across the Belle Fourche river, into a part of the state nearly devoid of paved road options and scant for river crossings of any roads. Our original storm attempt fizzled away as we drove beneath it near Volunteer, but a new storm developed rapidly in the upshear convective plume. That one, to our SW as seen from 9 NE Hereford, sported a much more robust updraft base and seemed to enjoy a nutritious blend of greater buoyancy and less entrainment (great taste, less filling?).

The storm was turning somewhat rightward with respect to the road, casting the increasingly precip-laden forward flank over the highway. Lots of other deep towers were erupting in all directions as well, including beneath the anvil of the main storm. This all forced a difficult intercept decision:
1. Continue ENE out of all the precip, wait potentially 1.5-2 hours for whatever was left of the storm (could be very messy!) to cross the Cheyenne River and get within good viewing range of a maze of mostly dirt roads on the other side, or
2. Cut S out of Enning toward Elm Springs on a dirt/gravel road whose maps advertised a crossing of the Belle Fourche River, figuring the road had to be at least passable if it connected two towns.

Being in South Dakota, we were wary of any option involving back roads, which quite often are in utterly wretched condition there. Nonetheless, we headed S, figuring the Elm Springs route would afford a decent one-pass opportunity to watch the storm approach us, then cross. It did.
Few other apparent chase vehicles appeared, so we had a reasonably peaceful viewing stops north of Elm Springs, including this pleasant westward view across golden wheat fields. As the storm drew closer, the arrangement of precip cascades in its forward-flank region offered some peculiar visuals.

Not desiring to be in the core, while on an unfamiliar dirt road, we continued S across the now-familiar Belle Fourche River to a spot just NW of Elm Springs, and let it cross to our N. At this time, the leading-edge updraft assumed a somewhat circular shape. A small, very weakly rotating convectively bubbly wall cloud formed, above a ragged scud tail related to the updraft’s inhalation of forward-flank outflow.

Within minutes, a separate area of outflow from an expanding rear-flank core demolished the whole regime. The entire storm then surged east, but not before offering a short yet spectacular CG show (photos looking NNW and then looking N), from what was left of the forward-flank area.

After the storm crossed into the road void of the Cheyenne River valley, it merged with other cells, grew upscale into a mess, and lost definition, leaving us in the unusual situation of “chase over” with plenty of daylight left. The next day would be a down day weatherwise anyway, with palatable supercell potential in better moisture slated for eastern SD day-3. As such, we cruised into Wall for lodging and dinner, anticipating the next day of photography and exploration in the uniquely beautiful Badlands National Park.

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