A mostly-marginal setup today across the Midwest offered a few areas of transient supercell potential. Down in the St. Louis area, an old outflow south of the metro near Waterloo was my initial target, but the storm in that vicinity could not get going. I ended up north of the city at Alton as a storm briefly went supercellular, albeit above its own outflow at the surface. The storm had some nice midlevel inflow banding curving into the updraft. The big show, however, was the lightning. Strong MLCape (3,000) and a puff of barely-20kt midlevel flow during the late afternoon turned this storm into a crazy CG lightning producer over Alton. Bolts struck both the Clark Bridge and the Melvin Price locks and dam. This was one of the few storms that prompted me to get inside the car for shelter while shooting.
I shot reaction-based stills and video during this event. I caught a couple of bolts on stills, but the video was better. The still frames extracted from this video show the nightmare that is CMOS rolling shutter. The many return strokes that most of these bolts exhibited made the video decent enough though.
A couple of stills:
And the video stills. This bolt hit the locks with upward leaders coming up off of the light poles:
Bolt hitting the north tower of the Clark Bridge:
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