The backshear is a protrusion of a multicell thunderhead’s anvil “backward” into and against the upper level winds, which were blowing from the left (SW) in this case. The stronger the flow, the more powerful the updraft needed to shove cloud material against that wind. Also, a big “knuckle”—common storm-enthusiast slang for upside-down moist convective towers—can be seen next to the notch, between the backsheared part of the anvil and the main updraft plume. Of all the hundreds and hundreds of supercells and organized multicell storms I’ve seen, some of which presented reasonably good examples of backshearing, I hadn’t bothered to take a good photo from the inflow side, until this one. That’s fine, too, because this was a textbook specimen!
Norman OK (26 Aug 6) Looking NW
35.2377, -97.4618