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.

Southwest Oklahoma Classic-HP Supercell

May 16, 2012 by · Comments Off on Southwest Oklahoma Classic-HP Supercell
Filed under: Summary 

Hollis to Apache, OK
13 Apr 12

SHORT: Chase route GCK-LBL-HHF-LTS-OUN. Intercepted occasionally photogenic supercell from inception near Hollis to N of Duke, then as it got absorbed into what became an HP “Stormzilla” NE of LTS that crossed Wichita Mountains. Activity forming SW of that merged/absorbed it after dark N of Apache.

The day before turned into a storm-free “bustola” on the western Kansas dryline, with only distant convection to the north near sunset. Elke and I salvaged something from the 12th by heading to Monument Rocks for the late-afternoon light, then bunked down in GCK.

Today’s most straightforward storm intercept target was over the NW TX, SW OK and SE Panhandle region near CDS. We left GCK for a long but simple jaunt SSE down US-81, with lunch in Perryton. While there, storms already started firing over central and SW OK. Early initiation stinks, especially when the observer still is over 150 miles away!

A distant line of building convection hovered just above the SE horizon as we headed out of Perryton. Now we targeted the area of its prospective backbuilding into the slowly retreating late-afternoon dryline. The pre-dryline baroclinic zone upon which the storms were forming was supposed to retreat N also, after 21Z. My thinking was that the future western storms would represent the latest, highest-CAPE development, farthest removed from the threat of interference by upshear convection.

Given our distance and target area, we obviously missed the Norman tornado, not that we would have targeted specifically that needle-in-haystack HP supercell event anyway. As we reached Wellington, big towers began to backbuild on the pre-dryline boundary toward the Hollis-CDS area; so we turned E on US-63 into SW OK to get into position. We fueled up at Hollis as a young storm began rotating ESE of town, and newer convection with cores formed to our S-SW near Vernon and CDS.

Using phone radar, I noticed a nasty-looking hook had developed on the W side of Norman, with an HP supercell attached to a larger cluster of storms extending westward. It was a mess, but a mess with a meso. I called my daughter, who told me she just had experienced a tornado at the high school and had been safe in a windowless room, under a desk. The first concern, and relief, was that she was fine. My son was elsewhere, well SE of the path. Both were OK, so I could shake my head and marvel at the truth that, once again, a tornado had occurred in Norman with me observing other storms far away.

We cruised E out of Hollis, preliminarily targeting the storm to our ESE, but with a contingency to stop and let the newer development to our SW (then the tail-end conceptual target) come toward us if it started looking good. That’s exactly what happened. CGs from the newly organizing, tail-end convection slammed all around us between Hollis and Duke. We turned N out of Duke, found a good vantage 3 N of Duke, let the disorganizing eastern storm move away to our NE, and watched the newer storm approach and strengthen.

Alas, still more convection formed upshear, but the storm began looking distinctively supercellular as it crossed the section road to our W. This would become the Altus-Apache supercell, but not before producing a nice wall cloud, one with strong rising motion but only modest cyclonic turning. Another lowered area, likely from an older occlusion visible in the last windmill shot, loomed in the background.

Neither got any better organized; indeed, the entire storm started looking somewhat strung-out. We considered breaking off and heading toward the newer activity W of Hollis and W of CDS, as some others already were. However, we needed a pit stop in nearby LTS, while the supercell began turning into a dark, menacing, precip-filled mass to our N. We decided to stay with it for awhile, watching what by now was an HP “Stormzilla” over the western nubs of the Wichita Mountains.

Our supercell developed a nasty-looking HP hook on radar with a deep, intense mesocyclone; but we couldn’t see anything in the dark murk from LTS regarding the tornado report near Blair. Even without the bathroom break, I’m not sure we would have been able to get in position to see much.

By the time we reached Snyder, it was to late to do much with the western convection before dark. We also knew that the storm would head into an awkwardly configured road void in the Wichitas, cutting us off. [I had circumnavigated the void successfully last November 7, but from a different angle. That day, I beat the storm. This day, the storm would beat me.]

Driving several miles N out of Snyder, we hoped to see whatever the storm had to offer before it got into that road void. Here was its S side, along the rear-flank gust front looking W. Here was the E side, looking NNW toward a small but slowly rotating cloud protrusion with a clear slot. That looked interesting for a few minutes, until being undercut by a massive surge of the heavy precip-loaded RFD.

The photogenic HP storm moved off into the road void to our NE, and we knew it would be dark by the time we could get through Lawton and go N toward Apache to see the storm again. The storm produced a rainy twilight tornado during that interval when we were repositioning, fittingly enough.

By the time we reached Apache to see what was left, we found a storm still supercellular but again messy. Our viewing timing with respect to the best-organized stages simply wasn’t working out. At least, for a short time, the downshear anvil region sparked mightily and beautifully overhead. Our last decent wide-angle view of the storm, from a hill just E of town, featured the lights of the wind farm and Apache to our W, what was left of the wall cloud and main updraft region near center (NW), the vault area to the right (NNW), and of course, cows.

Before the storm could cut off itinerary options again, we headed NE toward Chickasha and home. The storm merged with convection to its W, evolving into a small bow, then moving over Chickasha and toward the Purcell/Pauls Valley area a weakening blob of rain and occasional hail. By then, we were home, tired from the two-day, thousand-mile trek, but eagerly anticipating the big severe-weather day of the 14th.

A Real Stretch

June 1, 2011 by · Comments Off on A Real Stretch
Filed under: Summary 

Okeene and Karns, OK
23 May 11

SHORT: Observed small tornado W of Okeene OK and nontornadic supercell E of Greenfield OK.


This “day before the day” heralded the beginning of the long-advertised “undercutting Pacific jet”, and impingement of a strong, broadly cyclonically curved upper wind max over the southwestern CONUS as a 500-mb cyclone closed over the Pacific NW. I much prefer patterns like this for observable supercells than closed, stationary to retreating northern-Plains lows like we had just seen.

A strongly difluent upper height pattern spread over the southern High Plains late in the afternoon with subtle height falls occurring across much of the region. The presence of a dryline that was
1. Beneath those height falls and
2. Bounding the west rim of a rich moist sector (at least over the TX portion)
…was a high-confidence scenario, the specifics being maxima in low-level lift versus strength of capping into evening.

Accordingly, Jack Beven and I, in caravan with DF’s “Dude, Three Chicks and a Dog” chase team, headed W on I-40 to await storm initiation along the dryline in a strongly heated and increasingly moist air mass.

Along with Howie Bluestein, Dan Dawson, Jeff Snyder and other scientists and students accompanying OU mobile radars, we waited and shopped at the Cherokee tribal store on I-40 near Calumet, until echoes appeared to our SW, W and NW. We parted with the OU crews, briefly stopped to watch some high-based junk SW of Watonga, then targeted the much more healthy Fairview/Okeene storm.

In fact, the storms SW of Watonga were everything but photogenic; and we still were in transit northward Okeene when we caught a view of a suspicious lowering under the emerging base W of Okeene. In a rare event for me, my first photos on this day therefore were of a tornado!

By 1618 CDT, when we pulled over along a section road 3 S Okeene, the lowering had become a well-defined funnel cloud about 5 NW of us or ~4 W Okeene. It was tilted nearly horizontally (wide-angle with foreground storm structure), and already tornadic based in dust-whirl reports by closer observers. Time was 1618 CDT. The newer updraft base almost overhead seemed to be the next candidate for a mesocyclone formation/occlusion process; but it actually moved N and got absorbed into the forward flank, vanishing in the process.

Meanwhile, we witnessed, photographed and reported the 6-minute tornado from the same vantage as a debris cloud became more and more apparent (unenhanced and super-enhanced photo). Shortly before the tornado dissipated, the debris cloud got displaced astonishingly far S of where the condensation funnel met the cloud base. Clearly the stretching term of the vorticity equation was at play here.

We stayed with the storm for about 45 more minutes just E of Okeene as another small thunderstorm formed to its S, moved over us with frog-strangling rain and closely slamming CGs, then merged into the main updraft region. This pathetic state of affairs left the supercell demolished as a discrete entity. What was left merged into a massive multicellular morass extending some 70 miles E-W across the area. Now what?

Onboard radar feeds tempted us intensely with displays of a solitary supercell about 75 miles to our S near Gotebo, and there was plenty of daylight to head down there and spend some quality time with that storm before dark. Off we went, photographing a smaller cell to our SSW over Watonga. (which would become the supercell E of Greenfield) and later a distant presentation of the convective mass we had left.

That Watonga storm looked rather innocuous as we passed under its early updraft base in and S of town. However, by the time we reached Greenfield and around to the S side, the convection grew explosively into a full-blown young supercell with bright, hard-looking updraft towers boiling up the back side. The upward eruption of the convection easily was visible in real-time via our eyeballs, as was the onset of helical turning in the midlevels, white turrets and cauliflower tops rocketing skyward and veering rightward like daddy likes to see.

We didn’t intercept this storm; it intercepted us. The supercell blossomed right besides us on the way S, in an environment not seeming too different from more mature supercell to which we had been aimed; so we diverted from plan, maneuvering the backroads NE of Karns into the near-inflow region of the Greenfield storm instead. Its first mesocyclonic occlusion attempt happened just to our NNW with a well-defined, if elongated, wall cloud that rotated only slowly. Rotation tightened considerably after the mesocyclone became deeply occluded, slotted and nearly cut-off from the rest of the storm, having been kicked way back out the NW side of the storm. Alas, loss of buoyancy overcame stretching; and the circulation perished.

After that, several areas of weak-moderate rotation materialized along an increasingly elongated cyclonic-shear and convergence zone; but the supercell itself was getting weaker and more strung out. We left it and headed S on US-81 through El Reno, once again headed for the initially intended supercell still a little over an hour S of us; but that storm died before we got past Tuttle. Little did Jack and I realize we were crossing the path that a certifiably violent and deadly wedge tornado would take the following day.

We enjoyed seeing Jim Leonard in the field as well as the aforementioned OU folks, and had a fine dinner in Norman with Matt Crowther, Betsy Abrams, Greg Stumpf, and my beautiful bride Elke, who couldn’t chase on this day. It was a fine and fitting end of the “day before the day” setup. What a wild, frightening, intense, and historic day the “day after the day before the day” would turn out to be…

Next Page »