Sampling the Gust Front

May 18, 2009 by
Filed under: Uncategorized 

South-central KS and north-central OK
15 May 9

SHORT: Early supercellular structures then linear and outflow-driven complex observed.

LONG:
Once again we found ourselves headed generally NNW on a storm day with marginal midlevel winds likely to be dominated by frontal forcing, but with a weaker cap than on the 13th. Cu already were bubbling near the front/dryline intersection in the northeast TX Panhandle, but time spent analyzing the situation was too much to head that way. Too bad too; since a nice, tornadic HP supercell roamed those parts within another couple hours. Instead we decided to head N up I-35 to at least US-412 with the option of going W toward northwest OK or N into south KS, depending on convective trends.

Nothing had formed but the Panhandle storm and some cells well to our NNE in the Flint Hills by the time we got to the border, but it was obvious from visible satellite imagery that discrete linear backbuilding would commence very soon. By the time we rounded the corner westward at ICT, the anchor point for the frontal line was near Kingman, and by the time we got to Kingman, it was still farther WSW.

Still, we found two rotating updraft regions in very close proximity to each other, between Kingman and Harper. Looking NW, the northern member was small and shriveling further, but spitting numerous CGs from the NE fringe of its tilted updraft area. Looking WSW, the southern storm looked bigger and more robust, albeit somewhat high-based, but was about to be rammed unceremoniously by storms just upshear in the line. We dropped S and let that storm pass to our N and NE, whereupon it cleaved itself with an RFD cut and shrank into oblivion.

The rest of the afternoon was spent zig-zagging S and E to stay ahead of the massive outflow pool that had begun to build a long shelf cloud (here seen behind cornflowers just S of Anthony KS, as backdrop for a deployed sticknet unit about 13 W of Medford OK, and sheltering a CG 1 W of the OK-11/I-35 junction). For awhile between Manchester OK and Anthony KS, the anvil shield painted itself with numerous little streaks and puffs of mammatus, as if barnacles on the underbelly of an old oceangoing freighter. Occasionally a mobile mesonet or radar affiliated with V.O.R.T.EX.-2 would be seen, but the various field project vehicles seemed well dispersed.

The shelf cloud overtook us for awhile on I-35, occasionally stretching tubes of dust from distant (and non-tornadic) gustnadoes up toward scuddy fingers protruding from the lip of the shelf cloud. We did briefly stop on the S side of Perry to admire the strikingly sharp and clumpy textures of the shelf’s underbelly, which glowed with a dark and eerie slate-blue hue thanks to the heavy shadowing above, dense and light-absorbing core aft, and southern influx of late-day illumination from beyond the bow.

We got out from beneath that complex N of OKC, and ate a late dinner at the Cracker Barrel in Norman as that complex threatened to merge with a bow echo from the W. The gust fronts did come together over Norman, but with little fanfare save some cool breezes and a little over an inch of rain lasting past midnight. So ended our first (shorter) chase break of 2009, as a terrible western ridge and deep eastern trough pattern set in.

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