Oklahoma City HP Ice Machine

May 16, 2010 by · Comments Off on Oklahoma City HP Ice Machine
Filed under: Summary 

Oklahoma City to Ada, OK (16 May 10)

SHORT: Observed fast-moving HP supercell from eastern Oklahoma City to between Seminole and Ada, then let storm pass by into southeastern OK.


In the couple of prior days, I had considered some potential for severe storms across the region — mainly between I-40 and I-20 where it appeared the strongest midlevel winds would occur in a belt south of a mid-upper level trough over the central plains. The problems seemed to be lack of coherent initiative foci, rather weak moisture (resulting from the air mass to our S over TX being scoured by huge convective complexes), and weak near-surface winds that would keep hodographs small.

With far more negatives than positives apparent, I (along with many other storm observers) didn’t pay a great deal of attention on the day of the event. In fact, I was eating late lunch in Moore with Elke, Rich Thompson, Jack Beven and Jim Leonard — all experienced chasers of many decades in aggregate — when a supercell materialized out of a clump of convection NW of us near Okarche. The hook echo on the TV display and on our phones definitely got our attention.

Yes, a quick look at the surface map showed weak, mainly SW winds at the surface, though there was a sharply defined, E-W boundary extending N-NW of OKC. Turn the entire setup (including NW-SE storm motion) leftward 30-45 degrees, and you’ve got an east-moving storm with light SE winds. That’s not bad. Surface dew points in the inflow region were on the low side at about 62 degrees F, but the presence of the storm told us that was more than sufficient! Bellies full, we all scattered to our respective domiciles to get camera gear, and ended up separately observing the supercell.

Elke and I headed N from eastern Norman intending to photograph the storm coming over downtown, but its gradually accelerating motion precluded that. Instead, we first got a good look at it to our NW near the junction of I-240 and Sunnylane, with lots of buildings, wires and such contaminating the foreground. It was moving SE at 35 mph and accelerating further, and we had to head E on I-240/40 to stay ahead, if we wanted any hope at a good view without getting demolished by the baseball to softball size hail that was pounding northern and eastern Oklahoma City. We also drove right past the intersection of Choctaw Road and I-40, where a violent tornado had destroyed a truck stop and caused casualties the previous Monday. No time to look…we had to keep going!

Along the way there, we were listening to the radio simulcast of KFOR-TV, where Mike Morgan was saying, “We’re under attack at the KFOR studios! Skylights are breaking, baseball hail falling right here! We are under attack! This storm is taking no prisoners.” Now, Mike is not exactly the dignified, stoic gentleman of 1960s/70s television, seriously delivering the dire news of impending meteorological doom. He is no Harold Taft by any measure, and never could be. That said, while his penchant for over-exuberance and occasional exaggeration is well-known, he wasn’t too far from the truth this time.

Meanwhile, eastward we forged in search of a vantage. In this part of central Oklahoma, the Eastern Crosstimbers arboreal province, it’s very difficult to get a good view of a storm, with the trees, hills, and buildings rampant. We pulled off I-40 several times in futility, but finally and briefly found a very nice look about 2 SSW of Dale, on OK-102. To our NW, the north part of the storm (where the mesocyclone was) sported a beautiful tail (stinger) cloud, with a cream/reddish wall cloud rotating weakly. It was obviously being undercut by outflow and in no danger of a tornado. Given all the tornadic destruction of six days before, this was a good thing; because folks in these parts are hypersensitive to big, mean-looking storms.

I managed to photograph the south part of the supercell (looking W) before the storm closed in. We zigzagged S and E to Seminole, edging the hail core (nothing damaging), and driving past more of the previous week’s tornado destruction along Highway 9. Not wanting to get munched by a hail core in Seminole, we charged S to 12 N of Ada, and let the outflow-dominant storm race across the road right behind us.

All in all, this was an unexpectedly rewarding afternoon for a couple of storm observers who hadn’t counted on seeing much. Unfortunately, Oklahoma City took an epic beating from the hailstorm, the costs of which will run into the tens (maybe hundreds) of millions, not counting the insurance premiums that are sure to skyrocket even more. Since we stayed (mostly) ahead of the storm, I don’t have any hail photos, but the brief episode of photogenic structure near Dale was well worth the effort.

Four Supercells Seen from One Spot

November 7, 2008 by · Comments Off on Four Supercells Seen from One Spot
Filed under: Forecast, Summary 

Who Needs to Chase?
5 November 8

Even though I was committed by shift work to being at NWC through the evening hours, there wasn’t any pressing need to chase today to see supercells anyway. All I had to do was pay some intermittent attention to what was going on outside, watch them race by, and run out for a minute or two a few times to observe.

After several storms formed ahead of the west-central OK dryline, and in a narrow plume of favorably heated and moist boundary layer air, a visual treat ensued, which I was able to document in a few quick breaks from the priority of duty.

The first visible supercell moved past me well to the NW (Piedmont/OKC storm) as I drove in, but the sky was clean, and the base could be seen way off in the distance (sorry, no photos). I did see a ragged, scuddy wall cloud just above the horizon before losing sight of the storm. The next supercell moved NE from the CHK area over the W and NW part of Norman, exhibiting classical (if somewhat messy) structure in a wide-angle view, looking W. A zoom view shows a ragged, partly rain-wrapped wall cloud (strongly enhanced image), which showed (at best) very weak cloud-base turning. Upward motion of scud was rather slow too. Still, this storm was a well-defined supercell, visually and on radar, and and dumped a large amount of severe hail in a swath across the NW side of town. The mesocyclone area below cloud base soon became outflow contaminated, a process becoming evident in this view looking NNW.

A second, weaker supercell formed SSW of town, its forward-flank core heading right for us. A left-split updraft tried to calve off the forward (NW) flank of the storm (view looking SW), but didn’t last too long. The back side of the main storm, which passed over E Norman, caught direct and indirect light from the setting sun, and glowed almost otherworldly in pastel hues, making an uncommonly and delightfully tinted scene above the fall colors of local trees. The view in the last shot looks SE, which means that the light was reflected from the storm, casting unusual shadows and light angles for this time of day. Notice that the brightest light is on the left (NE) side of the trees!

The towers responsible for that reflection loom above a mostly silhouetted structure of “Battlestar Norman” in this view, looking ENE from the adjacent lawn. As the sun angle fell further, the hues warmed for just a few minutes (seen here looking ENE from the N side of the building). Even as the reflected solar glow faded, the hues of twilight kept the scene beautiful (wide angle, looking E). Not bad for November, eh?

That wasn’t all. A short while later, Ryan came in to request photography of a feature that looked a lot like a midlevel funnel, apparently sticking sideways (southward) from a convective deck to our WSW (crop-n-zoom on the feature). It was hard to tell if that really was a sideways, midlevel funnel or just a visual juxtaposition of two separated clouds. You make the call.

A well-defined left split peeled off another supercell (unseen) to our S. The anticyclonic supercell raced by us to the W, in the fading twilight, also leaving a swath of hail from the small but pronounced core on its S side. This is a mirror image of the left split showing classic skeletal structure, albeit high-based.

As for the broader event, as a whole and outside the line of sight from the NWC ground floor, it was resoundingly unproductive for tornadoes. All we had were a few cheesy tornado reports long after dark and outside of the 15%_SigTor (MDT) outlook area. What went wrong? My during-and-after interpretation of eyewitness observation, surface maps, soundings and radar inferences was that a blend of storm-scale and boundary layer thermodynamic failures was at least partly responsible. The storms were somewhat high based and spewing a good deal of cold outflow (as well as hail). Mesocyclonic occlusions and transitions to (cold) rain-wrapped states occurred quickly, resulting in insufficient time for circulations to form and wrap up tightly. Supercellular structures did improve during the sunset/twilight periods; but unlike in more moist events, MLCINH also ramped up quickly with enough surface T-Td spread to foment an unfavorable amount of cooling. Discrete supercells — by then E of I-35 — responded by shriveling away as they headed into the jungles of eastern OK.

What might this event have done had the dew points been 5 deg F higher? John H and I speculated on shift that we would have had a more buoyant and temporally longer lasting surface-based effective inflow layer, the better to take advantage of the enlarged hodographs beneath the early evening strengthening of the LLJ, and perhaps a bonafide multi-tornado event in that case. The citizenry of NW Norman should be glad for those lower dew points. Had that storm been tornadic, while still takin the same path (an unlikely thing, admittedly, given the forcing that differing storm-scale processes can exert on a storm’s motion) the path would have gone through some newly (last 10-15 years) developed parts of town W of I-35 and N of Robinson.

We see one sig-hail report from the Piedmont area storm (Rancho Rascovich being a supercell attractor of the highest order). The NW Norman supercell did dump a lot of hail up to nearly 2 inches diameter on several neighborhoods, busting windows and/or skylights in many homes where accompanied by estimated severe gusts, with glass breakage at the homes of several colleagues and co-workers who live in NW Norman. Elke encountered some falling hail ~1.5 inch diameter near and N of the YMCA (north base area) from a small core after dark, near the cold front.

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