6/22/2013 - NIU Undular Bore

The lapse below is from the NIU Meteorology Webcam System, which caught a spectacular undular bore followed by a few whelps. The bore and train was caused by a decaying mesoscale convective system (MCS). Note the radar image in the hyperlink is a couple hours before the passage of the bore; the bore and train itself was not associated with precipitation in DeKalb.  MCSs often produce arcus such as shelf and roll clouds, but this was a rather unique arcus type that was well removed from the parent -- dead! -- MCS. The continuation of the gravity wave was likely induced by an earlier training MCS in the region that may have, in concert with diurnal morning cooling, stabilized the boundary layer promoting an energy ducting mechanism.