Organized collections of thunderstorms known as mesoscale convective systems have been identified as producers of most of the rainfall in the tropics and in mid-latitudes during the spring, summer and fall. The Principal Investigator will continue his research towards an improved understanding of mesoscale convective systems (MCSs) and the atmospheric boundary layer. Under previously NSF sponsored research the Principal Investigator produced many significant new findings. Among these are the identification of the factors responsible for several distinctive features of MCSs. This line of research will continue with both observational and numerical modeling components. Emphasis will be placed on: 1. The dynamics of a region of low pressure which often trails MCSs, known as "wake lows" 2. The formation mechanisms of mesoscale vortices which form out of MCSs. These stable vortices are believed to be a triggering mechanism for future rounds of severe weather several hours after the original MCS has dissipated. 3. The controlling factors for series of MCSs which are often responsible for severe rain events. If successful, this research can be used to develop better numerical and conceptual models for the forecasting of severe MCS weather events.