Although May is the peak of tornado season in Oklahoma and the surrounding southern Great Plains states, we often go for many days in a row without storms as the troughs and ridges march by in slow motion. Things were looking good on Wednesday, May 11th – so much so that I banked up hours to take the afternoon off and go chasing. A negatively-tilted trough, ample deep-layer shear, surface dewpoints approaching 70 F got everyone excited, and SPC issued a moderate risk for the central portion of Oklahoma in their Day2 convective outlook.
Alas, it was not to be. Overnight, a shortwave trough ejected out ahead of the larger, negatively-tilted trough, and the resultant forcing for upward motion set off widespread convection. That morning, I woke up to find that most of western Oklahoma covered by a grungy precipitation shield, and that the SPC had dropped the moderate risk back down to slight. The rain was a good thing for the residents of western Oklahoma, who are experiencing levels of drought not seen since 1988. The net effect of the morning convection was widespread cooling and stabilization of the boundary layer. We decided to call our chase plans off and remain at work. We did have a little fun in Norman that afternoon when a portion of the line strengthened after interaction with an outflow boundary (rain-cooled air pushing outward) from an earlier round of storms, bringing us heavy rain driven by 30 mph wind gusts (at the Norman Mesonet station). A lot of folks at the NWC just stood by the windows and watched.