A diagnostic study of mid-latitude mesoscale convective systems

Two case studies of mesoscale convective systems (MCS) over the central plains of the United States were carried out using data from the SESAME experiment. The first case study makes use of high resolution data to examine the structure and evolution of a mesoscale cyclonic vortex within the convectively-produced stratiform region. The second case study containing lower resolution mesoscale data examines the influences of an MCS on the large scale and mesoscale.; Potential vorticity and its diabatically-induced Lagrangian time change is used to study the development of a mesoscale cyclonic system. Condensational heating in an ascending northward flow rapidly generated a region of locally large PV over a three to six hour period. The thermal structure and estimate of the Rossby radius of deformation suggests that a mesoscale vortex at the base of the mesoscale cyclonic system evolved towards a quasi-balanced state.; Apparent sources representing unresolved horizontal and vertical eddy transports are shown to greatly affect the heat and vorticity budgets around the time of maximum convection. Mismatches between temporal and spatial resolutions in the data also affected the heat and vorticity budgets.; Vertically integrated convective available energy (ICAPE) was found more accurate than traditional surface CAPE for identifying locations of initiation and continuation of convection. Low level convergence acting to release convective instability was shown to be strongly tied to convectively-favorable ICAPE changes.