The messy supercell, that I first intercepted a couple hours before west of Alzada, MT, had raced east-southeastward to Belle Fourche, encountering richer moisture along the way, and was fixing to move into town with hurricane-force gusts and 4-inch-diameter hail. As my late friend Jim Leonard said about another giant-hail-producing supercell he filmed in the mid-1980s, this storm was “serious business now”. Even among Great Plains supercells, it was exceptionally severe and dangerous. Here, only about a mile from where I stopped to shoot another speedy supercell the day before, we can see the wall cloud well. It was rotating fairly strongly, drawing inflow both from unimpeded warm sector and (in back right) from the forward-flank core, but couldn’t quite produce a tornado. That’s good for Belle Fourche, despite all the other destruction this storm wrought. This also was well-sampled by TORUS project mobile radars and mesonets, one of which measured a 91-mph gust in the rear-flank downdraft. Forward (right) and rear (left) flanks filled with intense, flooding rains and hail, leaving this large updraft base and mesocyclone to occupy the inner corner of the inflow a notch in between, shaped in two dimensions much like Pac-Man’s mouth. With this storm chomping right in my direction, I only lingered for a few more shots before escaping again through St. Onge, and down Interstate 90, only to watch another supercell form atop horizontal rolls in the warm sector, then merge with this one.
5 NW St. Onge SD (12 Jun 22) Looking WNW
44.6035, -103.7798