A Real Stretch

June 1, 2011 by · Comments Off on A Real Stretch
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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…

At Long Last: Birthday Tornadoes

May 31, 2011 by · Comments Off on At Long Last: Birthday Tornadoes
Filed under: Summary 

Hickory and Ada OK
21 May 11


This was my birthday. I never have seen a tornado on this date before this year, despite the seemingly ideal time of year for them.

Hold on! Tornado climatology isn’t always how it may seem. For strange cosmic reasons that shall remain a cryptic mystery, that date (green in the graph below) also is an inexplicable and pronounced low-day for tornadoes in the U.S. during this time of year, as shown by Chuck Doswell in one of his research papers published in the Electronic Journal of Severe Storms Meteorology.

Click to open an enlarged version:

The Intercept:
Elke and I headed S towards the northern rim of vigorous return-flow moisture near the Red River, followed by a unique chase team consisting of David Fogel, his cousins Samara and Ellie, and Ellie’s friend Ella, and of course DF’s equine-sized Leonberger dog, Porthos. [Note: This meant I was chasing with Elke, Ella and Ellie…good times!] Ellie and Ella were first-time chasers this day, giving me hope for some “rookie luck” to overcome my “birthday curse”.

Our target area was southern OK an north TX just E of the dryline, and we settled for the middle: The Red River, heading to GVT to fuel up and await nearby development near the northern nose of the most robust return-flow moisture. On the way down, messy supercells were evident in central TX, well S and Sw of the Metroplex and out of the target area; while a discrete storm rapidly intensified just SW of FTW. A convergence zone was evident in reflectivity imagery extending N from the FTW storm past ADM. This was our hot zone for hot action.

Not wanting to intercept a storm through the Metroplex if we could help it, we held firm at GVT awaiting closer development. That move paid off; as the FTW storm quickly (and rather inexplicably, given the strong buoyancy) perished.

After fueling and getting some technical difficulties fixed with DF’s onboard electronics, we waited a few miles N of town near I-35, admiring wildflowers and convective towers–yes, newly developed moist updrafts to our near WSW and more distant N. The northern towers, even through haze rendered by smoke from Yucatan crop-burning, looked healthier and began glaciating, as viewed across the verdant North Texas savanna. We had a storm to target, brother.

As we pulled onto the I-35 slab and headed N, strong reflectivity echoes started to appear NW of ADM. Those developed quickly into a strong echo, already resembling a supercell by the time we exited the slab and headed E on OK-53. Intense towers rolled up into the back side of the storm with fantastic buoyant force, as seen looking NE from W of Gene Autry.

Zigzagging E and N toward Sulphur, we met the first hilltop base view just in time to view a funnel suspended from an older, occluded mesocyclone to our NW (and W of town). By the time I could pull over safely, the rotation already weakened, the funnel more ragged and not as low, the clear slot cutting well around the cloud-base mesocyclone area.

Focus shifted to a newer area of cloud-base rotation to the E. The storm already was tornado-warned and had been for some time. That appeared justified. This supercell was moving into a very moist, low-LCL air mass with big (and growing) 0-1 km hodographs. This already was the most promising storm I had seen on a birthday, despite some unquestionable jackassery that ensued while viewing the newer mesocyclone area. None of the scuddy, rotating lowerings to our NNE (just E of Sulphur) could tighten up much, and the storm was getting away.

We needed to reposition, despite the lack of great vantages in that hilly and intermittently forested part of the state. Haze clearly was a problem too, and I knew we needed to be close to get better contrast. Before that area of storm-scale rotation could cycle back up, we headed through town. Our bright-eyed, twentysomething supercellular newbies from New Jersey, Ellie and Ella, got serenaded by the stereophonic wail of the Sulphur sirens, offering them an ominously palpable reminder of the menacing side of springtime in Oklahoma.

About halfway E on OK-7 to OK-1, the organization improved, all right. Obligingly, the storm that had been behaving itself during our relocation grew a very broad, extensive updraft base–all of which was rotating, and rather rapidly. Within the tumultuous gyre, every lowering was spinning in its own right, the whole system a seething, cloud-base cauldron of eddies and whirls that defied ready classification. We stopped 3 SSW of Hickory (and 1 W of the OK-1 intersection) to watch its merry-go-round of distinct funnels, shallow and bowl-shaped lowerings, and at least one brief tornado.

Some vortices were more than two miles apart, others adjacent. Where is the cutoff between a broad, multiple-vortex, weakly tornadic circulation, and a multiple-funnel (or multiple-tornado) area of storm-scale rotation? This thoroughly fascinating process unfolding to our NW through N blurred the lines between any such distinctions on the spectrum of atmospheric vortices. Sometimes, it’s just not as simple as categorically declaring tornado or not!

Two of the longer-lasting, lowest-extending condensation funnels (middle and left here, looking NW) initially developed apart at 1924 CDT, within the same mesocyclone. The eastern (right) funnel retrograded almost magnetically toward the western one, intertwining with it as in a seductive love dance. The combined condensation vortex then became more laminar, less scuddy, more wavy, and produced a brief, faint puff of dust beneath (deep crop-n-zoom/enhancement), in an area of very wet ground.

By 1926, the brief tornado was gone, the area of cloud-base rotation (at left in this shot) that had hosted the small, blended tornado vortex weakened. Did you notice anything to the slightly more distant right (NNW) in the last photo? Lo and behold, another area of rotation took shape to its NNE, itself offering a ragged, conical funnel that extended more than halfway down by 1927 CDT. If this was a tornado (couldn’t determine via enhancement or independent eyewitnesses), it was separate from the other, a circulation within a circulation within a circulation. These were far from the only funnels in the storm-scale gyre in just a 10-minute span. What a gloriously complicated mess!

The broader mesocyclone soon began tightening, and we needed to get E and N again to close in for more unambiguous tornado potential. In the process, we crossed a spot of infamy–the very railroad crossing where an agonizingly slow-moving train halted John Hart and I after we saw the distant Hickory tornado of 11 May 1992. That train 19 years ago seemed to go on forever, as the supercell got away, wrapped rain around its SW hook, and produced a multivortex F4 tornado just out of sight. Today, the tracks were clear and such agony didn’t befall us. The same road we couldn’t take way back then was open for business–right here, right now.

We turned NNE on OK-1 and drove almost under the rim of a (by now) very strongly rotating and more classical mesocyclone, stopping at a spot 1.5 SE Hickory when a broad cone funnel appeared about a mile to our NE. At 1934 CDT, a brief filament of whirling condensation rocketed up from the ground beneath the cone as I was exiting the vehicle, and before I could shoot…tornado! The condensation cone soon drew lower. Sinuous, partly translucent vortex filaments materialized beneath and coiled about one another, vaporous marionettes twirled by their tornadic puppet master. By 1927, the cone retreated to a smooth cloud-base bowl, and no vortices or debris could be seen beneath.

The mesocyclone began retreating NE, so we had to zigzag E and N to maintain view as it reorganized, retreated NNE somewhat, cut a deep clear slot, and intensified again. Heading E on unmarked road “E1700” 5 E of Hickory (a variably surfaced path of gravel, dirt and crumbling, antique pavement), we were very fortunate to find another high, relatively unobstructed vantage to our NNW and N.

Just in time, too…the mesocyclone cut a deep clear slot and began twirling funnels beneath with fervor (deeply enhanced crop). For a brief interlude, the spinning cloud mass dipped its southwestern margins into golden beams of sunshine, fluidly swirling together the concepts of atmospheric violence and beauty.

The circulation seemed to plant itself on the earth, chunks of scud forming right down to the ground, ripping across the surface at tornadic speeds, interspersed with intermittent but unmistakable suction vortices–one after another, none lasting more than a few seconds, but collectively, too many to count. This was a very low, humid, multiple-vortex carousel. Sometimes two vortices could be seen interacting while scud and/or suction spots whizzed through other areas of the magnificent maelstrom.

[Some described this tornadic stage as a “wedge”, but the condensation was too ragged, sparse and ephemeral to call it that. Still, if viewed with any blockage by trees or terrain, I can see how such a mistaken description could be made.]

The last evidence of a tornado was at 1953; thereafter the cloud base rotated much more weakly and rose in height. By now, we knew of the larger, newer and stronger supercell W of Ada, but the clearest path to it up US-377 still was blocked by our weakening (yet still potentially hail-bearing) storm.

After letting that supercell pass across the highway, we had a smooth trip to Ada, barely in time to see a conical lowering below the horizon (turned out to be the end stage of its last tornado at 2035 CDT) while still driving. By the time we found a place to stop, a small and ragged funnel remained. No matter, we could marvel at the spectacular storm structure spreading across the western sky. As this storm moved NW of Ada and began weakening, assorted precip shafts cascaded from the cloud base near low-hanging scud chunks, likely yielding any remaining “funnel” or “tornado” reports.

The short but happy drive back to Norman led to a delicious dinner, steak and shrimp for the menfolk, whatever the ladies wanted, kibbles for Porthos out in their vehicle, all in a festive celebration of a fantastic storm-observing day (and for me, the clinching win on the restaurant TVs that sent the Mavericks to the NBA finals). Birthday tornadoes that didn’t hurt anybody, great storm structure, Mavs clinch a playoff series…a great, great day indeed!