hailstones

Mulhall to Stillwater and Ripley OK
14 Apr 13

SHORT: Intercepted marginal/intermittent supercell–pretty storm–between Mulhall and Perkins OK.

LONG: Another day waking up during the late afternoon, after a night shift, offered a conditional opportunity for storm observing. In a year already shaping up to be sparse for such activity, this day offered at least marginally suitable wind and moisture profiles along or near a cold front, somewhere between OKC and southern Kansas.

One major concern was that any storms forming along the front, near and N of the KS border, would be undercut by the frontal air mass; so I played wait-and-see with shallower convection to its south. Finally, a clump of deep towering cumulus became apparent on visible satellite imagery NW of OKC, giving that look I’ve seen many times before of an incipient storm genesis area. Seeing that, I plotted a likely storm-motion vector that would take any resulting activity across I-35 W of SWO, threw the gear into the vehicle, and zigzagged to the Interstate to engage the prospective quarry.

As I passed downtown OKC, I could see deep towers to the NNW-NE glaciate. Radar reflectivities showed growing echoes in the same area, the spawn of the upward-motion zone responsible for those early towers. By the time I got to the high overlook near Mulhall, a series of mostly high-based and small (but deep) towers to my WNW-W were evolving into a more discrete and distinct storm.

From even these early stages, the storm was pretty, but had a pronounced core plummeting through the middle that limited the size of the upshear part of the updraft. This general configuration continued throughout its remaining lifespan, although the updraft did grow appreciably as it approached I-35 and moved into higher-PW boundary-layer air. I headed E to SWO a.k.a. Stillwater a.k.a. Stoolwater, then as the storm assumed marginal supercell characteristics, dropped back S toward Perkins to let it approach. The storm was high-based as expected, outflow-dominant, still with a small updraft, but severe-warned due to hail.

Knowing the tornado potential was next to zero, I let the rear-flank downdraft pass overhead then followed along behind the storm for a potential sunset view. In the Ripley area, still on the back edge of the rear-flank core, I encountered some hail up to about 8/10 inch in size, and reported that via the NSSL-PING app. A garishly painted tour vehicle zoomed east, into the core; but I opted for the colorful side of the storm, spread out beautifully across the eastern sky into which its slowly shrinking form receded. The earlier high-PW air began to be offset by diabatic surface cooling, and the storm spun down from the Perkins area eastward.

Cool, earthy aromas of fresh rain, melted hail and slightly pounded vegetation was welcomed by a chorus of frogs–something very seldom heard in these parts during the past couple of hot, drought-inflamed years. This was the full-sensory experience of storm observing, where even the feel and taste of the air was fresh, clean and wholesome.

After relaxing and enjoying the experience for a spell, I headed back through Perkins for a quick bite of fast food, then S down US-177, I-40, OK-102, and OK-9. It was a fun “backyard” chase that was most welcomed, while still getting me home in time to spend some time with my daughter and beautiful bride (who stayed home) before work.

Yuma CO, 21 Jun 10

SHORT: Observed 3 supercells ultimately merge into one over Yuma CO — damaging hail, beautiful post-storm skies.

LONG:Join us on this fine, toasty day for a tale of three supercells that became one, the hellish hailstorm that resulted, and a storm-observing couple who chased them.

Elke and I began the day in Sidney with a target area of NE Colorado, in the region of relatively backed low-level flow. We were uncertain whether the storm(s) of interest would fire on the Front Range or on a convergence boundary farther E, in somewhat more moist air SW of Sterling. The answer: yes, and yes! From Sterling, we observed the growing anvil from a storm near DEN that was high-based but starting to rotate aloft (based on radar velocity imagery), along with multiple towers bubbling just to our SW, beneath and S of the anvil canopy.

The tower at left, in the last shot, erupted into a pre-supercellular supercell, before anvil shadowing had a chance to mitigate diabatic heating of its immediate inflow layer. We dropped S to stay ahead of both this storm and the more distant and growing beast roaring out of DEN. Even in this early stage, the new storm displayed nice corkscrewing action (the base of the DEN storm becoming visible at distant rear), looking W from the N side of the Colorado Plains Regional Airport (AKO). The storm spun around for a short while, moving slowly closer to us without growing a very large updraft. Meanwhile the DEN storm churned along essentially straight toward us, with a wall cloud and lowering becoming faintly visible in the distance under its southern flank. I sensed this closer storm wasn’t long for the world.

We headed E through Yuma, taking note of potential hail shelters for four reasons:

1. The combination of the big western storm and any merger with a foregoing supercell could spawn some healthy ice bombs,
2. I still had a good windshield and didn’t want to bash the hell out of my new vehicle with gorilla hail this soon,
3. We deemed it wise to plan sheltering options in case we didn’t have time to bail S of Yuma and ahead of any storm acceleration, and
4. The next major town to the E was Wray, its S escape option (US-385) known to be under heavy construction with a surely nerve-wracking and possibly vehicle-destroying situation of one-lane, pilot-car closure for many miles!

Meanwhile, another tower went up in some slightly more strongly heated air several miles farther S (to our SW), also evolving into a skinny supercell rather quickly, and likewise coming under the sprawling and thickening anvil of the onrushing western storm. In the last shot, from just E of Yuma, the outflow-surfing updraft base of the massive western menace is visible at distant left, and its downshear anvil canopy distant right — dwarfing the nearer but much smaller supercellular plume. The older tower (spinning down to its N) eventually merged with the northern part of the newer, closer supercell as the latter expanded. Then it expanded further and assumed some sharply sculpted structure, moving slowly E and expanding its updraft still further.

One thing it did do, before being absorbed by the big bad brute impending, was glow forth an eerie, ghostly layering of light and shadow, interspersed with subtle pastel hues, a weird sight that I’ve seldom seen to this extreme. Back under its SW flank, the near storm developed a circular, slowly rotating, mottled texture to its main updraft region, and even sported a ragged, conical lowering for a short time. What could this storm have done with an extra hour or two before being swallowed by the expanding, ever-intensifying convective Pac-Man stampeding eastward toward us…and it?

The western storm charged onward, turning more deviantly rightward such that its main mesocyclone region — now an HP “stormzilla” with suspicious lowerings in its “notch” area (actual view and deeply enhanced zoom) would go just S of Yuma — while the value or near-forward flank region would absorb our nearby supercell virtually overhead. A short-lived lowering that preceded those photos raised a tight little plume of dust, but due to distance and poor contrast, we’re unsure if it was tornadic.

Though expected, this event still lit a sense of foreboding within, as if billions of icy little swords of Damocles dangled high above. This merging maelstrom of mayhem accelerated too, sure to turn into a destructive tempest of a nastiness and ugliness that we cared not to endure unsheltered. Time to get into town and under that covering!

Surprisingly, we scooted under the canopy of an abandoned drive-in restaurant after only one other car: the county sheriff. Only once the hail began did other vehicles seek room there — most in utter futility. Much as when it was the place to go in Yuma for icy treats of another kind…first-come, first-served! Within ten minutes, hail up to 2 inches in diameter started hammering away on the tin roof, becoming dense in coverage and ear-splitting in loudness. Vehicles that couldn’t fit got a glass-busting, steel-denting beatdown.

Although we had been hailed on while in a vehicle on several occasions, Elke and I hadn’t yet experienced a rip-roaring hailstorm together from under outdoor shelter. It was quality time as a married couple — at least, once I stopped yelling over the deafening din about the camera lens I couldn’t find. We had a blast.

I actually remembered to shoot some video of this with our new HD camcorder (video being something I’m not accustomed to doing after several years without), while also firing off a few hi-res DSLR stills with the lens that turned out to be in my left hand the whole time prior. One of those stills captured the a rare, split-second scene indeed: a hailstone exploding upon striking the pavement. It reminds me of some artist’s conception of an asteroid striking the moon, minus the fireball in the locus of impact.

After the beating was over, we secured a room at a little yellow motel. The lady who ran the motel mentioned that her daughter owned a restaurant and bar in town, Main Event, that was open and serving dinner late. Outstanding…we could avoid the usual storm observer’s conflict between getting dinner before early, small-town closing times and heading out for photography!

We headed a few miles SE of town to examine field hail and photograph the beautiful late-day, post-storm light (looking NE and looking WNW). Here are a few nice examples of that hail, about 45 minutes after it fell (culled from grassy, protected areas):

Variably opaque core, clear outer layer with numerous radial bubbles

Same stone silhouetted against the sky to illustrate its translucence

Different stone, larger opaque core

Two hailstones: Entirely opaque and rounded, the other asymmetric, broken and of mixed opacity

Right before the sun sets, four hailstones on a gravel road [Would this compel Lucinda Williams to re-title one of her best-selling songs accordingly?]

While looking down at the hail, don’t forget to look overhead! Upon doing so, we saw sunset-lit fractocumuli shedding condensation vortices, including this ragged funnel and a separate, fishhook-shaped horseshoe vortex that wandered off to the E, slowly spinning down on its own for many minutes in the warming colors of the late-day rays (zoom). Here’s the western sky at the time.

All manner of fascinating processes were happening. Off to the SE rose a skinny, tilted tower, elevated atop the shallow stable layer from the earlier storms, seemed to be divided into two stepwise manifestations of the same convective plumes — one rooted just above the boundary layer, and a second slanted along some higher surface, with a backshear on the W side of the upper layer. Meanwhile, off to our E, dark wisps of scud passed placidly in front of a gorgeously glowing tower in the back side of the MCS. All of this while immersed in the luxuriantly earthy scent of rain-soaked farmland, while western meadowlarks sang from all sides…

We were getting hungry, though; so we cruised back into town for what turned out to be a very good meal at Main Event. I recommend the place for a late dinner if you end up anywhere near Yuma after a chase.