Was in Napa Valley last week (California) for work. On the way back from lunch, and just as we approached the office, a dust devil spun up among the grape vines right before our eyes. Looked very nice as it picked up some soil. It then crossed the road, over the manicured lawns, and in the process picked up a bunch of leaves and other assorted stuff which nicely revealed the still intense vortex, and then it then moved right over the building unbeknownst to those inside - a definite F0 ! Temps were high 30s and very hot soil, so super-adiabatic lapse rates in play.
If you have your own dustdevil pics / encounters, throw them up here!