Wednesday, June 6, 2007 — South Central NE


A painful cap bust in the central Plains, despite an incredibly deep surface low for June.

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The potential for an historic severe weather outbreak was on the table with a broad, progressive trough ejecting onto the Plains, resulting in cyclogenesis in the lee of the Northern Rockies, with a surface low bombing out to under 975 mb as it traversed the Northern Plains. Obviously, that's huge by June standards. The dynamics associated with this potent system were comparable to a powerhouse early spring trough, with a 60 kt LLJ and 80-100 kt flow at 500 mb; and yet the thermodynamics were forecast to be exceptional too - the best of both worlds, it seemed. But, as usual, the setup wasn't without a caveat: a very warm mixed layer was forecast to advect over the Plains from the SW ahead of the trough, making capping a serious concern. If there was one "all or nothing" setup in 2007, this was it. Shame it turned out to be the latter, because the "all" that could've been given widespread initiation may have rivaled some of the best chase days this decade.

The days leading up to showtime were filled with the same enthusiasm and heavy activity in the online community that's been present so many times this year with potentially big setups. With the amount of instability and shear depicted ahead of a sharp dryline emenating from a low deep enough to rival the SLP readings of strong Nor'easters, it became hard for some of us to keep in mind that a bust was even possible. Surely something as petty as the cap couldn't really stop our once-in-years setup from realizing its potential! The only thing worrying me were the logistics involved in making it to a target in NE/SD and back without missing too much work, and the same was true for Bryan and Brandon now that they had started their summer classes. However, we resolved those issues by the day before, though we knew we needed to be back by Thursday morning, which had the potential to yield a marathon overnight drive home depending on how far we went.

While the synoptic setup changed very little on the models leading up to the event (save for the usual slight slowing/deepening trend), surface moisture ever-so-slightly decreased with each run, making the cap bust potential even more dangerous. It eventually seemed that the only "safe" target was near the surface low in SD, where initiation was likely during the afternoon (though strong tornadoes were not all that likely); farther south, prolific instability would be locked underneath an inversion for most of the afternoon, and whether or not it could eventually punch through and take advantage of the equally staggering dynamics would make the difference between a day for the record books and a hot, sunny afternoon.

We decided to target the area from north-central KS to central NE due to our time constraints, a gamble that could pay off in glorious ways if initiation occurred. Not wanting to have to get up early and rush all day Wednesday, we departed Norman at 9:00 PM Tuesday night, arriving in Salina by 1:00 AM and grabbing a room at the Quality Inn (after trying at least five or six other motels that were booked!). The 0600 UTC day 1 outlook extended the pre-existing moderate risk farther south, all the way into far N KS, and placed much of our target area under 15% hatched tornado probabilities. This was greatly encouraging after the disappointing developments of the previous 24 hours on the models.

We lounged around Wednesday morning and didn't depart Salina until about noon, when we decided a drive north towards Grand Island was in order. By this time, the new SPC outlook showed reduced tornado probabilities and cut them off farther north, which was more than a little upsetting. It was plain to see why: concerns some chasers had expressed over moisture return failing to live up to model predictions were validated, as dew points of only 59-61 deg. F were common throughout much of KS and NE, with only marginally better moisture showing up in OK and TX. Clearly, even strong moist advection was not going to boost surface dew points into the 67-72 deg. F range that was being counted on for the mega-outbreak to verify. As if this wasn't bad enough, a fairly solid cirrus deck had already moved overhead by the time we woke up, and extended as far west as the eye could see. Strong cap + poor moisture return + inhibited surface heating = chasing disaster.

We shot straight north on US-81 to Hebron NE before deciding there was no point in getting any farther from home given the latest developments. We grabbed lunch and perused the data for awhile, with the situation looking even more grim, as dew points had not improved at all since we'd left Salina. The day-of model runs, while generally painting a bleak picture with little or no precipitation anywhere on the dryline, hinted that one possible area for miracle initiation was over W to NW KS, so we decided to start heading back and leave open the possibility of flying west after anything that went up. By the time we got back to Salina, I had lost all hope in the day, but Bryan and Brandon decided it was worth heading west so as not to be impossibly far away if that miracle did happen somewhere between Dodge City and Hill City. We took an interesting detour by using a lengthy dirt road to get from I-70 to Carneiro after encountering a major backup on the interstate, then proceeded southwest to Great Bend. We arrived around 6:30-7:00, and finally called off the chase since satellite showed no hope of initiation and solar heating was on the decline. After stopping in Wichita for dinner, we made it back home by 11:30.

This was the longest single chase of the season, and yielded no convection whatsoever; however, it wasn't nearly as painful as Mar 24, when Bryan and I drove to the same area, only to turn straight around after busting, without a break. That said, this was an extremely frustrating way to (probably) end the season, since the parameters were nearly off-the-charts. Most chasers agreed that with moderately better moisture return, this almost certainly would've been something talked about for years to come. A few tornadoes did occur in W SD and E WY, but the main show on the dryline never happened, and so, for those of us who can't afford regular drives to the Dakotas for marginal summer setups, the 2007 chasing season went out with a whimper, despite ending up pretty good overall - for those lucky and skillful enough to score on most of the big days, anyway.