(Abbreviated MCS.) A cloud system that occurs in connection with an ensemble of thunderstorms and produces a contiguous precipitation area on the order of 100 km or more in horizontal scale in at least one direction. An MCS exhibits deep, moist convective overturning contiguous with or embedded within a mesoscale vertical circulation that is at least partially driven by the convective overturning.
A Mesoscale Convective System (MCS) is a complex of thunderstorms which becomes organized on a scale larger than the individual thunderstorms, and normally persists for several hours or more. Mesoscale Convective Systems may be round or linear in shape, and include systems such as tropical cyclones, squall lines, and Mesoscale Convective Complexes (among others). Mesoscale Convective Systems often is used to describe a cluster of thunderstorms that does not satisfy the size, shape, or duration criteria of an Mesoscale Convective Complex.