With the anniversary of the Joplin tornado less than a month away, I thought I would look again at what weather systems were in place that contributed to the event. It hit me today, after looking at the archived synoptic 21Z (4:00 PM) weather map from May 22, 2011, that Joplin was in the vicinity of what’s known as the “Triple Point.” According to NOAA, the Triple Point is defined as “the intersection point between two boundaries (dry line, outflow boundary, cold front, etc.), which is often a focus for thunderstorm development. A triple point also may refer to a point on the gust front of a supercell, where the warm moist inflow, the rain-cooled outflow from the forward flank downdraft, and the rear flank downdraft all intersect; this point is a favored location for tornado development (or redevelopment).” I knew there was a cold front out to the west, but I did not realize (or I forgot) that there was also a low pressure system and a dryline moving through SE KS/NE OK. (I should note that SPC had much of the area out ahead of the front in a categorical Moderate Risk by Sunday morning.) The Triple Point during severe weather season often has the greatest instability, highest wind shear, and lift. Often you’ll hear of storm chasers choosing to target the Triple Point. I know all about these dynamics by now, but prior to the Joplin tornado, I knew less about the Triple Point. So after all these years, it makes more sense to me why the Joplin area was so susceptible on that day.
