Many of the factors that are critical for understanding and predicting weather that is disruptive to human activity occur on what meteorologists term the mesoscale. Mesoscale phenomena are not well sampled by the operational weather network; therefore, progress is made through episodic field experiments specially designed to study mesoscale processes. The Principal Investigator has two objectives using data sets from already completed episodic field programs. The first is to calculate budgets of water, sensible heat, momentum and potential vorticity and to examine the magnitudes of frontogenetical processes in the context of mesoscale convective systems. This data set is unique in that it allows, for the first time, all terms in the budget equations to be calculated. A numerical model also will be used to help in interpreting the results. The second thrust is a collection of studies aimed at elucidating the structure and dynamics of mesoscale convective systems. These studies include climatologies of radar data over the U.S. and Europe and numerical modeling.