The scientific focus of the Mesoscale and Microscale Meteorology Division is divided into two themes or programs. CaSPP (cloud and surface processes and parameterizations) strives to quantify the large-scale effects of mesoscale and microscale processes, and to develop physically based methods to account for these effects in large-scale models. PPWS (prediction of precipitating weather systems) strives to advance the understanding and prediction of significant precipitation events in order to substantially reduce forecast errors toward the limits of predictability. Many projects involve aspects of both "themes."