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.

Oklahoma City HP Ice Machine

May 16, 2010 by · Comments Off on Oklahoma City HP Ice Machine
Filed under: Summary 

Oklahoma City to Ada, OK (16 May 10)

SHORT: Observed fast-moving HP supercell from eastern Oklahoma City to between Seminole and Ada, then let storm pass by into southeastern OK.


In the couple of prior days, I had considered some potential for severe storms across the region — mainly between I-40 and I-20 where it appeared the strongest midlevel winds would occur in a belt south of a mid-upper level trough over the central plains. The problems seemed to be lack of coherent initiative foci, rather weak moisture (resulting from the air mass to our S over TX being scoured by huge convective complexes), and weak near-surface winds that would keep hodographs small.

With far more negatives than positives apparent, I (along with many other storm observers) didn’t pay a great deal of attention on the day of the event. In fact, I was eating late lunch in Moore with Elke, Rich Thompson, Jack Beven and Jim Leonard — all experienced chasers of many decades in aggregate — when a supercell materialized out of a clump of convection NW of us near Okarche. The hook echo on the TV display and on our phones definitely got our attention.

Yes, a quick look at the surface map showed weak, mainly SW winds at the surface, though there was a sharply defined, E-W boundary extending N-NW of OKC. Turn the entire setup (including NW-SE storm motion) leftward 30-45 degrees, and you’ve got an east-moving storm with light SE winds. That’s not bad. Surface dew points in the inflow region were on the low side at about 62 degrees F, but the presence of the storm told us that was more than sufficient! Bellies full, we all scattered to our respective domiciles to get camera gear, and ended up separately observing the supercell.

Elke and I headed N from eastern Norman intending to photograph the storm coming over downtown, but its gradually accelerating motion precluded that. Instead, we first got a good look at it to our NW near the junction of I-240 and Sunnylane, with lots of buildings, wires and such contaminating the foreground. It was moving SE at 35 mph and accelerating further, and we had to head E on I-240/40 to stay ahead, if we wanted any hope at a good view without getting demolished by the baseball to softball size hail that was pounding northern and eastern Oklahoma City. We also drove right past the intersection of Choctaw Road and I-40, where a violent tornado had destroyed a truck stop and caused casualties the previous Monday. No time to look…we had to keep going!

Along the way there, we were listening to the radio simulcast of KFOR-TV, where Mike Morgan was saying, “We’re under attack at the KFOR studios! Skylights are breaking, baseball hail falling right here! We are under attack! This storm is taking no prisoners.” Now, Mike is not exactly the dignified, stoic gentleman of 1960s/70s television, seriously delivering the dire news of impending meteorological doom. He is no Harold Taft by any measure, and never could be. That said, while his penchant for over-exuberance and occasional exaggeration is well-known, he wasn’t too far from the truth this time.

Meanwhile, eastward we forged in search of a vantage. In this part of central Oklahoma, the Eastern Crosstimbers arboreal province, it’s very difficult to get a good view of a storm, with the trees, hills, and buildings rampant. We pulled off I-40 several times in futility, but finally and briefly found a very nice look about 2 SSW of Dale, on OK-102. To our NW, the north part of the storm (where the mesocyclone was) sported a beautiful tail (stinger) cloud, with a cream/reddish wall cloud rotating weakly. It was obviously being undercut by outflow and in no danger of a tornado. Given all the tornadic destruction of six days before, this was a good thing; because folks in these parts are hypersensitive to big, mean-looking storms.

I managed to photograph the south part of the supercell (looking W) before the storm closed in. We zigzagged S and E to Seminole, edging the hail core (nothing damaging), and driving past more of the previous week’s tornado destruction along Highway 9. Not wanting to get munched by a hail core in Seminole, we charged S to 12 N of Ada, and let the outflow-dominant storm race across the road right behind us.

All in all, this was an unexpectedly rewarding afternoon for a couple of storm observers who hadn’t counted on seeing much. Unfortunately, Oklahoma City took an epic beating from the hailstorm, the costs of which will run into the tens (maybe hundreds) of millions, not counting the insurance premiums that are sure to skyrocket even more. Since we stayed (mostly) ahead of the storm, I don’t have any hail photos, but the brief episode of photogenic structure near Dale was well worth the effort.