Robert Simpson and Jeff Logsdon
National Weather Service Northern Indiana
On a day characterized by pulse-type thunderstorms, most of which remained below severe limits, one isolated supercell was able to develop during the late afternoon hours as a result of multiple boundary interactions. During the early morning hours of June 19, 2009 a mesoscale convective system (MCS) pushed southeast through the great lakes region ahead of a warm front that extended from the southern tip of lake Michigan through the southeast corner of our county warning area (CWA) in northwest Ohio. The resulting outflow boundary pushed the warm front south into central Indiana and provided an initial cap to any surface-based convection through the morning hours. Elevated convection was able to form around midday near the Indiana/Michigan state line above the surface cold pool. This convection pushed another strong outflow boundary south through northern Indiana. At the same time, the warm front was pushing back northward as afternoon heating overcame the stable low level air. This presentation will examine the interaction of these two boundaries and the subsequent supercell development and also explore possible explanations for tornadogenesis failure with this storm.