The supercell that rotated the wrong way

I'm standing in a bean field at dusk and there's a supercell on the horizon, huge and green, but it's spinning the wrong way — counterclockwise in the northern hemisphere, which just doesn't happen. The rain is falling up, and all my instruments are reading calm. I keep thinking, this is the one that breaks the rules, and I'm not scared, I'm just trying to get closer before I wake up.