The Fifth-Generation NCAR / Penn State Mesoscale Model (MM5) is a limited-area, nonhydrostatic or hydrostatic, terrain-following sigma-coordinate model designed to simulate or predict mesoscale and regional-scale atmospheric circulation. It has been developed at Penn State and NCAR as a community mesoscale model. Mesoscale Meteorology is the study of weather systems smaller than synoptic scale systems but larger than microscale and storm-scale cumulus systems (horizontal dimensions generally range from around 5 kilometers to several hundred kilometers).