Jeff, it's interesting that you guys noted the vortex was to the south, but you guys chose to go south. ...
Your situation may have been slightly different. You mention a known primary area of circulation to the north so going north far might not have been good. Seems that also implies that you guys were generally under / near the inflow flank / extended rainfree base. You wonder where the tornado came from, but often such flanks develop secondary areas of rotation even though more minor than primary and often these don't show on radar much at first, but you also mention you didn't have radar at the time.
The ground circulation was E of a N-S road that we figured we might be able to use to stay to the west of it. The tornado appears to have moved NNW towards the area where the unintentional storm chasing convoy was located. We knew the main meso was to the north near Jewell, where significant structural damage was being reported. Again, we figured that, with any eastward movement to the tornado path, we could safely get by to the west of it by driving southward. At the time we first saw it to our S, it reminded me a bit of some of the brief spin-ups that folks drove by on Hwy 160 between Attica and Harper, KS, on 5-12-2004. Of course, this was associated with a fatter elephant trunk funnel aloft. I'll try to pull a vid cap of the funnel when I have a chance later this evening. We would have preferred to have blasted eastward (which is what we were planning on doing), but muddy roads quickly precluded that. We did have escape options to the N, E, and S, though. Unfortunately, E was impassable for us (thick mud), and N was getting closer to the primary meso, which we didn't want to mess with since we didn't know what was in the precip. So, we aimed for the south option.
From a storm structure stand-point, I'm not sure where this tornado came from. The RFD gust front was considerably east of our longitude, and it looked like the primary hook echo and associated cyclonic meso was more than several miles to our north. We talked about the possibility that this was an anticyclonic tornado to the S of the cyclonic meso to our N, but the winds experienced match a cyclonic vortex and don't match the flow pattern of an anticyclonic tornado. This odd storm structure seemed to catch all of us off-guard (assuming Tim Samaras and the mobile mesonet crew wouldn't intentionally position themselves to be hit by a tornado).
Interestingly, if we hadn't seen the funnel, we probably would have continued to make our way south back to Hwy 14 with little consequence, and we may well have attributed the windy conditions to being, well, behind the RFD gust front in a supercell. Instead, when we spotted it to our S, we cautiously waited and crept slowly eastward and southward so as to stay out of its path.
If nothing else, this goes to show that, in the presence of a strong tornadic supercell, always be aware of "side-show tornadoes" or areas of rotation may may occur well removed from the primary meso (even in the south of the primary meso behind the RFD gust front, apparently)! If we had been stupid and were only trying to get up-close video, I'd feel much worse about this. Then again, this thing only side-swiped us (I think we escaped to the west of it). As it was, this run-in seemed less dangerous than some of the close-up wedge video from last week (not to downplay the damage and minor injuries inflicted on Doug and his chase partners!!), though anytime one gets caught off-guard by a tornado in close proximity it is seldom a good thing.
I'm still worried that, eventually, someone will get tagged by a drill press or wedge after getting stuck in mud in the path of the tornado (or having a car breakdown that precludes them from driving out of the path). With as wet and muddy as some of the roads in NE and KS have been recently, the threat of getting stuck on a muddy road and nailed by (a) massive hail or (b) a significant tornado is enhanced quite a bit.
