Evolution of environmental conditions preceding the development of a nocturnal mesoscale convective complex

The region where the MCC experienced its most intensive growth was initially characterized by dry and hydrostatically stable conditions (associated with the passage of the previous MCC) above the shallow, wedge-shaped cold air mass. In less than 3 h, interaction between the diurnally varying low-level jet and the frontal boundary led to a local increase in convective available potential energy (CAPE) of over 2000 J kg^-1 for air parcels averaged through a 50-mb-deep layer immediately above the frontal surface. The region north of the quasi-stationary surface front became a favored zone for nocturnal MCC development when 1) particularly high CAPE arose due to the transport of moist air northward above the frontal surface; and 2) adiabatic mesoscale ascent, which was particularly strong near the northern terminus of the low-level jet, resulted in significant cooling above the jet axis. -from Authors