The “HP Drum” Storm
Delhi/Clinton/Greenfield OK, 12 May 10
SHORT: Observed HP supercell from S of Delhi OK to Clinton area, with some lightning after dark near Greenfield.
LONG:
The main surface cyclone was ejecting northeast over Kansas with a slowly progressive cold front southwestward across NW OK and into the TX Panhandle, intersecting the dryline in the extreme eastern Panhandle. I normally don’t like cold frontal setups such as this for tornadic storms, with upper flow nearly parallel to the front and barely rightward of the dryline. Still, with the boundaries intersecting only a couple of hours to the west, dew points in the mid 60s to near 70 F in the moist sector, and 50-60 kt 500 mb winds aloft, in the eastern Panhandle region in mid May, it’s advisable to chase. The basic ingredients of moisture, instability, lift and shear would be there. The biggest question, of course, would be the relative geometry of kinematic fields and boundaries, offering a dominant tendency for linear storm mode.
Ryan and Corey, whom I had chased with the two prior days, had other obligations on this day of more marginal tornado potential; so I hopped in the truck and headed W on I-40 to await the day’s convection. It was easy to ignore a rapidly-moving, leftward-deviant hailer down by LTS, and wait near W edge of a thick cirrus plume for heating back along the dryline.
Towers kept erupting along the cold front and feeding NE into a backbuilding line, which I preferred not to go after. Storms also were forming off the dryline into SW OK, but almost instantly turned linear as well. Instead of going after either right away, I hung out near Leedey for a spell, shooting around an abandoned homestead while waiting for the convective mess to sort itself out better.
Sometimes linear messes do break up into supercells, and that happened here. The activity to my SW began to knot up into inflections and semi-discrete embedded storms, one showing increasing rotation on the N end near Erick. As I headed down that way, it got tornado-warned, apparently producing a brief one early in that cycle. By the time I got there, the storm was nearly featureless and photographically unworthy, a hopelessly huge cascade of cold rain falling into its inflow from yet another intensifying, embedded supercell farther SW.
I dropped S out of Sayre and intercepted this storm with a big, robust velocity couplet near Delhi, not knowing yet that Mike U and Matt C (who had been hanging out in the eastern Panhandle for a few hours) already had abandoned their initial target, dropped SE, and had seen a brief tornado with it down near Vinson. As this drum-shaped, heavy-precip (HP) monster came into view (24 mm wide angle), a tremendous, frightening and dangerous barrage of CG lightning to its NE (and all around me) reminded me how little lightning we had seen with the tornadic storms the previous two days! It also kept me inside the truck, only briefly opening the window to shoot an occasional photo as the storm churned toward me.
There were good east, southeast and northeast escape options, so I could hold this typically more treacherous viewing position for longer than usual, until either the HP mesocyclone got too close or the hail got too big. If this sucker were to produce a tornado again, the most probable way to see it would have been from within its path to the NE. At one point, it seemed willing! Alas, the feature had far more rising motion than rotation, and devolved into a scuddy tail.
When the nasty part of the storm’s core got close, I zigzagged NE toward OK-152 E of Sayre and took that road to Cordell in incremental fashion, occasionally lurching E to get out of vault hail that started beating on the vehicle before the stones got big enough to cause damage. That’s what was going on as I took this wide-angle shot back toward the mesocyclone, looking SW from a point 8 SSE Elk City. The low-hanging, scuddy area was rotating, but not alarmingly fast, with a clear slot drawing around. That was the best that occlusion process could do, however, and I kept going along 152 to stay ahead of the huge hail that surely made life miserable on some farmsteads soon thereafter.
I was repositioning through a remote area NE of Cordell and E of Bessie, at a relatively distant position, when the storm produced the brief spinup along I-40, and couldn’t see it in the dark murk. After dark, and after the storm go N of I-40, it turned somewhat more leftward again, its propagational component and mesocyclone each weakening with time, while persistent nonsupercellular storms formed on its SW flank. The complex yielded several episodes of CGs (photographs 1, 2, 3) after dark between Greenfield and Watonga before I headed home into the last of the 70s dew points for some time to come.
Comments
2 Comments on The “HP Drum” Storm
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Dann Cianca on
Sun, 16th May 2010 2:11 pm
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tornado on
Sun, 16th May 2010 6:22 pm
Beautiful pictures, Roger.
Thanks, Dann. I missed the brief tornadoes, but came home satisfied with salvaging some HP storm structure and lightning from what could have been a messy, linear day.
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