Feeble Central Colorado Storms

August 12, 2008 by · Comments Off on Feeble Central Colorado Storms
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Franktown to Broomfield CO
16 Jun 8

SHORT=LONG: After the adventuresome chase of the 12th, and photographing abandoned buildings with the Doswells on the 13th, the pattern aloft turned to the dreaded Rockies ridge, shutting down even the most marginal chase opportunities for several days and sending us to the DEN area for some R&R at Elke’s mom’s place. Starting on the 16th, enough flow began to sneak through the ridging and enough moisture began to creep back northward in the boundary layer that we again became concerned for supercell potential in the great Plains. One target area was for high-dewpoint HP storm potential in southern OK and north TX, 8-9 hours away. A secondary but far closer threat practically was in the back yard: high-based storms on the Palmer Divide near the mountains, with barely enough shear to consider some storm rotation potential.
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Supercells and Funnels near Emporia

August 12, 2008 by · Comments Off on Supercells and Funnels near Emporia
Filed under: Summary 

Eastern KS, 12 Jun 8

SHORT: Supercells intercepted W and S of Emporia, then pretty sunset shelf in Flint Hills between Eureka and El Dorado. But there’s so much more…

LONG: We started the day in Council Bluffs IA, across the MO River from OMA. A cold front — reinforced by outflow from the line of storms that we had observed the evening before — had moved through the area and was decelerating a few hours’ drive to the S. After a little bit of analysis, it became clear that we would have to head into northern MO or eastern KS to have any decent shot at seeing a supercell on this day. Storms probably would fire earlier, with a very slightly greater chance of a tornado, in northern MO, but in unfriendlier, hilly terrain with hazier sky and lots of small towns to hold up the interceptor’s progress. Had that been the only option, we would have sucked it up and gone there. I’ve lived and chased in northern MO before, so familiarity with the area has helped both when I had to observe storms there, and when I decided not to. Today, we decided not to.

Instead, we targeted the southwestern section of the front, under somewhat weaker winds aloft, between the south-central KS dryline and the MO border, specifically mentioning EMP as the place to go. The fastest — not necessarily shortest — way to get there was to head down toward MKC then SW along I-29, I-435 and I-35. When we reached STJ, we knew these things:

  1. The boundary was nearby to our S and moving at a crawl.
  2. We were hungry for lunch.
  3. There are plenty of chow sources in STJ.
  4. We would have no problem with laptop card reception in a big town like STJ to browse over lunch.
  5. In the unlikely event things changed enough in 2.5 hours that the east-central KS option soured, we simply could adjust to the nearby secondary target of northern MO (with less stern-chasing than if we rounded SWward first then changed our minds).
  6. This mild, moist, overcast air on the N side of the boundary would not heat up the car’s contents (namely our camera equipment) while we ate, unlike if we stopped S of the boundary in MKC, OJC or EMP.

Lunch at Ryan’s “feeding trough” was very good, as usual, and examination of surface and satellite imagery said, “Go SW, young persons.” TCu already were bubbling along the area of maximized convergence, just N of the front-dryline intersection, between ICT-EMP. The EMP target was looking great, which allowed us no guilty conscience or second-guessing over totally blowing off some slowly developing storms not far ENE of MKC. A couple of tornado reports eventually came from those storms when they got to northeast MO, but nothing significant nor well-documented, that I’ve seen so far.

By the time we hit EMP, the TCu had blossomed into several young Cb. Great timing! The nearest was to our N, as seen from near Americus, merging with a line of towers and showing weakly supercellular characteristics such as diffuse midlevel striations, tilted updraft towers, a ragged, weakly rotating (at best) wall cloud. We briefly contemplated keeping up with it, but instead targeted a darker visual area to our WSW that represented a rapidly strengthening storm on radar (still getting good card reception from EMP nearby).

We headed S from Americus to US 50 just W of EMP to intercept the storm’s projected path between Cottonwood Falls and Plymouth. By the time we got past that first rise W of EMP — the one that always gives Elke and me peace and gratitude upon entering the marvelous Flint Hills from the E — the storm loomed directly ahead of us to the W. We had driven this stretch of road several times while staying in the Flint Hills for exploration and landscape photography (not chasing), and the sight of a big, fat supercell looming ahead actually was quite peculiar in such a familiar place. Even though a collective anvil shield lowered contrast, it exhibited classical supercell structure — bell shaped, with striations, NE-leaning inflow tail, and tilted updraft towers on the rear flank. By now, “Three Dudes and a Dog” (DF, Roman, Keith and Thunder) had joined us, after driving the more direct route from OMA-BIE-EMP.

Two areas of cloud-base rotation formed beneath — both visible here as wall clouds, the southern one over the road and the northern one beyond a clump of trees. The northern wall cloud, though more ragged, dominated and persisted, and even developed a stubby, conical and somewhat ragged funnel. The cloud-base mesocyclone broadened while also strengthening. This is counterintuitive to those who employ the infamous ice-skater analogy, but can and does happen sometimes when a storm’s vorticity value increase by other means is greater than the negative effect of loss of stretching. Seeing this rapid development gave us some hope for tornadogenesis, if the circulation in turn could tighten again. Alas, that same rotational invigoration hauled a bunch of rain around the wall cloud and obscured good view of the most interesting area.

By this time, with precip wrapping up the mesocyclone and other storm’s precip areas beginning to impinge upon ours, I thought this one was about finished. Lo and behold, with absolutely astonishing speed (5 minutes!), a brand new wall cloud and very tight low level circulation formed on what had been an invisible occlusion point farther E, and to our NW. At 2308Z, one small, rapidly spinning area under the base tapered into a conical funnel and developed very low toward the ground (24 mm wide angle view about 20 seconds later). This easily could have been a brief tornado, hut we could not see evidence of any debris or dust above the distant tree line — either then or while super-enhancing the photos later — in order to be certain. Its location would have been about 5 NW Plymouth in extreme NE Chase County — stony terrain with grass, shallow soil and few structures, and not a very friendly area for confirming weak tornadoes. If any other observers were closer, they couldn’t confirm it either, based on the lack of tornado reports from this storm in the daily rough log, and I wasn’t about to report it as anything more than a funnel without just a little better evidence. [The next storm to the SW had a couple of reports in the same county later the same hour.]

The wall cloud itself looked even more classical and menacing a couple minutes later without the funnel, rotating broadly but obviously, then developed another very low-hanging area of vigorous spin that looked like it could plant a “fat hose” very quickly; but we couldn’t confirm ground contact before it became diffuse and rain-wrapped. After this, unfortunately, DF, Keith and company separated, with them heading SW on the turnpike to get closer to the next storm sooner.

Though the SW storm was getting intense pretty quickly, this one didn’t appear done yet. I’ve learned not to give up on storms too soon, lest they pull last minute surprises, so we zigzagged NE toward Americus once again to stay with it for a spell. The next occlusion formed quickly but also got bifurcated and undercut fast. I now was losing confidence quickly for any mesocyclonic tornadoes with this storm and was about ready to bail, when a thinly rain-wrapped, nonmesocyclonic funnel — the best defined and longest lasting funnel of the day for us — appeared unexpectedly in the damnedest of places: under the shelf cloud of the rear-flank gust front to our W! We couldn’t confirm ground contact here either, nor could a few other reliable storm observers I know who witnessed it from varying distances. The funnel (shown here at 2335Z) lasted four minutes before narrowing and dissipating.

I spent just enough time messing with the gust-front funnel that the surging, increasingly bow-shaped mesocyclone area to our N cut off the north road option. By now, the SW storm was sitting on I-35 in Chase County, and we didn’t want to risk not being able to turn around on a limited access road with very few exits, and an HP supercell rumbling right up the tollway. So we made the stoplight-infested transect of EMP, then headed S of town to await the arrival of the SW supercell. Of course, it did produce one confirmed, small, rain-wrapped tornado while we were tangled up in town. After some zig-zagging, we found a decent W vantage at the EMP airport – at least, as decent as a late-afternoon, poor-contrast HP can afford. Awaiting us were Chuck and Vickie Doswell, who had been there for a good 20 minutes or more and couldn’t see the tornado from that distance. As the storm moved NE toward the town of Emporia, a big, blocky wall cloud came into view to the W, soon expanding somewhat, then developing a pronounced, persistent, bowl-shaped lowering that extended over halfway to the ground beneath. Once again, we couldn’t detect any evidence of damaging ground circulation.

That storm also rapped in rain (surprise, surprise, eh?). With dusk nigh, we all called off the active part of the chase and decided to head down to El Dorado for dinner and motel rooms. Up we cruised into a less-traveled, somewhat flatter, but still gorgeous stretch of the Flint Hills than the northern part described so deeply by Heat-Moon in PrairyErth. That truly is green carpet country at this time of year. Up there on the elevated, tallgrass prairie, the earth seems to fall away from horizon to horizon. I’ve been through this stretch of US-54 a few times, but never with its skyscape so splendidly bathed in stormy colors and textures. This experience made a wonderful ending to the chase day. Due to darkness, we ignored a supercell to our SW, threading just N of the meat of its forward-flank core.

In El Dorado, we found rooms and ate a rather bizarre dinner at the only place still open (barely!) — a Chinese restaurant that was out of almost everything on the menu by the time someone finally remembered to serve us. The hosts were very apologetic, and gave us whatever was left from the kitchen. The food actually wasn’t bad, and for those who had it, neither was the wine. Before we turned in for the night, Elke and I spend a romantic few minutes together behind the motel, in light rain, quietly watching a nice lightning show off to the SE. It was hard to imagine, there and then, that we had begun the day in western Iowa!

Despite the difficulty of visibility imposed once again by unfriendly HP storm structures, I was satisfied with the chase overall. The forecast target worked great, in that we saw two supercells and three funnels within 10 miles of EMP, and that twilight experience in the Flint Hills can’t be done justice with words alone, or even photos. The storms themselves were rainy messes (what else is new in 2008), but I’ll take this over any of the many seasons in which I saw few storms and/or no tornadoes at all.

The next day, we headed NW with the Doswells to tour and photograph some abandoned farmhouses and schoolhouses near Ellsworth, before parting ways. I also released Black Betty II (our latest pet black widow spider) at an undisclosed location that will provide her with plenty of shelter and isolation from humans, as well as abundant bugs to prey upon. Her new home will be much better for her, and for us, than where we found her (our garage). She accompanied us on our early June chases, devouring assorted insects and spiders we picked up along the way, entertaining Fogelissimo, Chuck, Keith and other curious onlookers at various times, and generally living the good life in her jar. I guess taking a dangerous but beautiful spider along on our chase trips is becoming a tradition of sorts.

It was great to spend some time with the Doswells on the 12th, and of course, with DF, Keith B, Roman and Thunder earlier, while taking in the splendors of stormy skies in KS. All these folks deeply appreciate not just the stormy skyscapes but the landscapes and the many facets of the Plains experience. Elke and I were honored and grateful for their company, before they all had to disperse homeward.

Stair Stepping Several Supercells

August 7, 2008 by · Comments Off on Stair Stepping Several Supercells
Filed under: Summary 

LeMars to Defiance, IA
11 Jun 8

SHORT: Difficult stair-step chase. At least 5 tornado-warned, line-embedded supercells intercepted in NW/W-central IA. Several tight HP mesocyclonic wrap-ups observed including rain wrapped tornado near Pierson.
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