A Tale of Two Supercells and a Firehose

September 4, 2007 by
Filed under: Summary 

Oberlin and Ulysses-Hugoton, KS
19 Jun 7

SHORT: Separate tornado-warned Kansas supercells intercepted from inception NW of HLC and SW of GCK. Lightning, rain, wind, hail encountered day and night. Hard but rewarding finale to chase vacation.

LONG: We left LBF around midday with NW KS as the target area, near a triple point along the W edge of a warm front. On the way to MCK, we saw towers with fuzzy bases and obviously elevated inflow layers firing N of the warm front, an encouraging sign for the rest of the chase day. I had been worried about capping, but that was soothed some by the convection already happening on the “cool” side. What I didn’t expect to happen so early in the day was a solitary supercell to fire along the warm front.

Northern Supercell

While we were eating lunch at the MCK Runza, Rocky called to let me know about the explosive, singular storm firing near HLC. This was within reach, but I was somewhat leery of 1 p.m. development on a warm front. By the time I saw some data across the street at a motel, the storm already showed strongly supercellular characteristics on radar, and could be seen through fractocu and haze to our SE. Indeed, by the time we crossed the KS border it already had been TOR-warned.

We drove down US-83 toward Oberlin, on course to intercept what promised to be a slow-moving but HP-evolving storm, in marginal upper level winds. I was hoping some of the more clearly surface based towers on that segment of the warm front closer to us would erupt, and they did — fast. As if on request, a dense conglomeration of congestus developed with accommodating alacrity, forming an elongated Cb with a dense but small core and (at times) several updraft bases. We were vacillating between whether to wait for this complex to sort out a supercell in an environment similar to what spawned the HLC storm, or leave it and go after the initial supercell. It’s a good thing we stayed near Oberlin, because we would have missed the reported tornado W of HLC by a short time anyway, and also missed the development of a pretty supercell S of Oberlin.

Our storm built a broad updraft base with several short-lived, early wall clouds (looking WNW and later looking NW). It developed a banded, tired structure and “cold” appearance of the base (looking NW), leading me to believe it was a little to far on the wrong side of the warm front, but then GLD tor-warned the storm and another wall cloud developed (with slow, recognizable cyclonic turning, but never any fast rotation). From S of Oberlin, we let the storm churn toward us until it accelerated, apparently hitchhiking on some cold air that had begun a southward plunge. Still, intermittent small wall clouds with weak rotation sprouted before wrapping in rain.

That storm got “cut off” by new development immediately to its SSW near Selden — a storm which, in turn, quickly became shelf-like and somewhat turquoise in appearance as the cold air from the NNE plunged underneath.

We wanted to get ahead of the original supercell — by now an obvious HP mess, but still a somewhat discrete storm. However, its backbuilding cut off our S option on KS-23 between Hoxie and Grainfield, forcing us to go way W then S through Oakley and beyond to have any shot at getting ahead. As we blew S of Oakley, a large outflow pool blew past us, signaling messy things for whatever was left of the HLC storm by the time we could round the corner on it again. Its southward discrete propagation — far faster than the ambient mean flow — cut off our E intercept option out of Scott City, so we plunged all the way down to GCK. This is when the chase got fun again.

Southern Supercell

By now well ahead of the outflow, we noticed explosive new development W of GCK, near the dryline. It seems so simple to find a place to watch a storm on the supposedly flat, open high plains of SW KS, but in practice it isn’t. We drove for many miles S of GCK on 83, blocked by trees, hills, wires, buildings…you name it, at every attempted stop. As a result, I missed a short opportunity to photograph some nice silhouetting of the new storm against the translucent white anvil of the original complex, the latter by now charging relentlessly toward DDC and looking like a giant, murky dungeon of slate-gray in the northeastern sky.

Our storm still was by itself and youthful, and began to take a hard right (S) turn after calving off a split or two. We charted an intercept course W on 160 toward Ulysses, storm abeam to starboard. We stopped occasionally to watch a classically beautiful show of mammatus above the golden wheat, as well as distant, low-contrast views of wall clouds and other lowerings (super-enhanced zoom) under the increasingly broad and well organized updraft region. [Ultra-enhancement of images of the above lowering and those of several others revealed some low scuddy protuberances and/or dense precip shafts within precip areas, but nothing certifiably tornadic.]

The convection above the base was solid and very prominently rotating visually, in the midlevels. Meanwhile, just as we were deciding to let it get closer to us, anvil CGs started flying way ahead of the area of interest, cutting down on outdoor viewing opportunities for two people.

As we stopped in Ulysses for a bathroom break, the supercell churned equatorward but at a rate still considerably slower than the movement of its CG barrage. Anvil strikes started slamming all around us, making me glad to be in town with a lot of higher objects around. We finally booked it out of there, somewhat regretfully since the storm was by now tornado-warned and I wanted to see into the murk better. But the nasty barrage of CGs in its path continued unabated.

Spooked a little by all the high, tall CGs flying out ahead of the storm, we stayed about 15 miles to its S between Ulysses and Hugoton. Still, there were enough CGs also in the more immediate vicinity of the updraft, as well as the core to its NE-E, that I could get quite a few visual snapshots of the low level mesocyclone region.

Meanwhile we shot loads of wide-angle images of the storm, its low level striations, and some peculiar, curved midlevel cloud bands that would arc in uncanny concentricity around the storm’s south periphery, as if rings orbiting a giant gas planet. Then above the low level bands boiled a convective cauldron fully worthy of 70s dew points on 3500-foot high plains elevation! It was amazing to witness the hardness and motion of its convection, still quite visibly rotating, coiling helically upward with a speed I’ve seen only in much stronger shear situations and big tornado outbreaks.

Eventually the low and midlevel clouds got thick and began to hide more and more of the structure, while a long inflow tail to our E-N evolved into more of a shelf cloud because of outflow surging in from the Hill City/Dodge City complex.

Our Version of Jonah and the Whale

Atmospheric puzzle pieces were starting to come together in my head with a clarity that was at once illuminating and very disturbing, for the sake of our safety over the next few hours. To the distant SSE, we spied the sunset-lit cloud shield from the AMA-CVS area line, which was expanding. To our NE, the HLC-DDC complex that dogged us all day was backbuilding into our Ulysses/Hugoton supercell, which itself had begun to backbuild to its W and NW and look ever more outflow-controlled. To our ESE, the NW Oklahoma MCS was eating westward into the moist air as if it were a giant, fast-growing convective tumor, and obviously would merge with the KS complex somewhere over the NE Texas Panhandle. Meanwhile the AMA MCS looked like it could expand NE or E and eventually merge with the combined KS/OK complex. There we were, in the inner locus of a giant shark mouth that was snapping shut in slow motion. I realized the race was on to stay out of merging and expanding MCSs for as long as possible.

With such an uncommonly steamy air mass available, I figured there was nothing to stop just such a process, and that if we had any hope of escaping these impending mesoscale jaws of doom, it was to fly SSE on US 83 through Canadian to Shamrock and beat the raging monster to relative commuting safety at I-40.

It was a great plan! Too bad it wasn’t an even greater one, because didn’t [i]quite[/i] work. By the time we made a necessary gas and pit stop at Perryton, outflow winds were slamming the area so hard that standing up was difficult, and the station’s canopy overhead rocked to and fro with a rhythmic, rusty squeal. Still, I thought we had a shot to barely beat the converging mass of purple reflectivities and shoot the closing gap through Canadian. We did come within no more than 5-10 miles of doing just that, but ultimately those few miles just weren’t available to us.

We managed to make it as far as just NW of Canadian before we couldn’t outrun the zipper effect anymore, and the wind began to include progressively more rain and lightning. Then..SLAM! Over a hill and around a small curve awaited an unseen 20 foot long tree branch covering most of the road, which I ran directly over at a nearly unbraked 60 mph. All sorts of racket erupted under the lurching car as the branch crumpled under us. This wasn’t the place to disembowel a vehicle or even suffer a slow breakdown from a tire leak! Fortunately we didn’t take any damage, probably because the branch was very wet and green and flexible, being from a notoriously soft-wooded tree (cottonwood).

The next hour and a half was spent driving in a storm observer’s most challenging conditions: Dark, mainly two-lane road, very heavy rain, frequent/close/blinding CGs…dodging tree limbs, downed signs and other road debris across much of three counties, and in two different construction zones just to add to the fun. At one point I couldn’t help but run over a crumpled black heap of metal something-or-other on the north side of Wheeler, compelling me to stop, get out, and check the best I could for tire leaks or other damage amidst the rain and lightning.

Then came a tense and slow drive through mainly zero visibility to Shamrock as the three complexes came together directly overhead, a giant firehose unloading right down onto us, CGs popping all around and intermittent hail peppering the car. Still dodging downed branches almost everywhere that trees line the E side of US-83, I had no idea if one or more tires already was slow-leaking or an oil pan was cracked open, under the distinct possibility we would become disabled and stranded out there at any given minute. Let’s say I didn’t feel like joyfully humming Hosannas through fields of periwinkles at that stage of the trip.

It was a big relief to get to Shamrock, and even more so to check the tire pressures there and at Sayre to find no leaks or other damage. Same for the undercarriage, which amazed me considering I ran over some large stuff along the way. We got lucky, along with having a damn tough vehicle. However much longer this car lives — and it’s got over 194K on the odometer now — I’ll be grateful that it lasted this long considering the terrible beatings I’ve caused to be administered to it off and on for years, and for its steadfast service in this and other situations up to this point.

Our mood buoyed by the reassurance of vehicular integrity, we rode home on I-40 appreciating the occasional whole-sky eruption of crawlers, often punctuated by towering CGs, the wet green countryside briefly alight with the brightness of a cloudy day upon each such grand display. Our chase vacation ended in majestic, difficult and sometimes treacherous fashion, and we didn’t arrive home ’til nearly 4 a.m.


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