We tracked this supercell from Nebraska to South Dakota, over a distance of 800 miles, in June 2008. We were driving 95 miles an hour to avoid getting swallowed by this thing, and then we'd stop for just a few seconds to snap photos. The idea is to stay in the sweet spot, away from the storm's precipitation, and follow it while it develops. Warm, moist air fuels the cloud until it can't hold any more, and then it blasts out gusts of cold air and rain. This was taken right before the storm dropped golf-ball-size hail on us.