Chase Log: March 12th, 2006

Click on any of the SPC products below (Convective Outlooks, Watches, or MCDs) to see the SPC's "Severe Thunderstorm Events" page pertaining to this event.

MAP

Total Distance: 600 miles
Target Area: Independence (KS)
Chase Area: Near Independence to Fort Scott (KS) to Miami (OK)
Maximum SPC Risk category: High
Watches: PDS Tornado Watches 73, 74, and 77, Tornado Watches 75, 78, 79, 80, and 81, Severe Watches 69, 70, 71, 72, and 76
Mesoscale Discussions (MCDs): 253, 255-275

The models had been forecasting one of those once-a-decade type of March synoptically-evident tornado outbreaks for several days prior to this event. Unfortunately, the GFS had forecast similar high-end setups twice within 7-9 days previous to 3/12, neither of which really panned out. So, there was a little skepticism regarding model forecast verification, which required cautious optimism on my part. In addition, NAM and GFS runs the previous couple of days indicated that the dryline would push into Arkansas by afternoon. Since it was spring break, I was thinking about biting even when it looked like that would be the case.

By the time I awoke on the 12th, however, NAM, GFS, and RUC runs all indicated that, instead of the dryline pushing all the way through eastern Oklahoma, the afternoon position of the dryline would actually be quite near I35 (a tad east). Wow, a change for the good! Models were still indicating seasonably-high Tds in the 63-70F range, which pumped CAPE forecasts into the >2500 j/kg range. A 110kt 500mb jet streak was poised to round the base of the upper-level trough to the west and head into the plains by afternoon. The "big-time" action looked to be up along a warm front that stretched from a ~992mb low in nc KS, eastward through northern Missouri and central Illinois. Very strong low-level shear, along with high Tds (for March), certainly justified the High Risk issued on the 6z SWODY1. Aaron Kennedy and I talked about whether to bite on this, but we both opted to leave that high-end target given the very fast storm motions forecast in unfamiliar, chaser-unfriendly terrain (not to mention the 6pm sunset time). I debated a little about heading into northcentral Texas, where surface flow was progged to be a little more backed than areas to the north. However, I had strong worries about initiation, and we the dryline holding farther back than we had anticipated in the days leading up to this event, I figured I could make a run to southeastern Kansas, hoping to end up in western Missouri by 0z (where the 12z NAM was forecasting 1500 CAPE and >300 0-3km SRH).

Phil and I teamed up with Robin and Dan, and we left for the target area about 11:30am. Interestingly enough, an intense supercell trekked through Kansas City a few hours earlier (where Tds were in the 30s and temps were in the 40s). To make a long story short... We weren't able to get on the initial supercells that developed in far eastern KS in the early afternoon, and we ended up waiting around Independence for most of the day. Surface winds veered to the SSW direction across most of the area ahead of the dryline, resulting in relatively weak convergence. In addition, and against model progs, dewpoints in the se KS and eastern OK area slowly dropped into the 58-60F range as the boundary layer deepened with relatively strong mixing. Convection did initiate about 5pm in se KS, but they looked incredibly sheared over and rather unimpressive. As night fell, convection filled in and moved eastward into MO. We dipped south a bit into extreme ne OK, but weren't able to really get onto anything. The storms were hauling to the E and NE, so we called the chase off. I was surprised it took so long to initiate dryline convection in eastern KS and OK... *shrug* ... It was nice to see a storm at least, but it really looked like the storms didn't have enough CAPE to really do much, at least until dark and until they moved into MO... Oh well.

Overall, this was the second most prolific tornado outbreak in March, behind only March 13th, 1990 (which featured an F5). The fast storm motions (>55mph in many cases) did result in some long tornado tracks, and there was one violent F4 tornado. In addition, there was one remarkable supercell that tracked from extreme northern Oklahoma, through southeastern Kansas, central Missouri, central and northeastern Illinois, and northwestern Indiana, before finally dying on it's way into Michigan. This supercell had incredible structure through most of it's very long life. There were other, long-lived supercells that aligned in the "string of pearls" fashion across Missouri and Illinois, however.