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Meso-β-scale Characteristics of an Episode of Meso-α-scale Convective Complexes

Ray L. McAnellyColorado State University, Department of Atmospheric Science, Fort Collins, CO 80523

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William R. CottonColorado State University, Department of Atmospheric Science, Fort Collins, CO 80523

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Abstract

A variety of meso-β-scale (20–200 km, <6 h) temporal and spatial characteristics associated with the life-cycle of the meso-α-scale (200–2000 km, >6 h) convective complex (MCC) are described. The analysis is based on a typical episode of MCCs in the central United States. Thunderstorms in the MCC are generally well-organized into meso-β-scale convective features. The larger MCCs are typically preceded by several of these meso-β convective clusters or bands, which tend to be aligned along linear meso-α-scale features such as the eastern slope of the Rockies or thermodynamic discontinuities evident in hourly surface or satellite data. The intense development of these larger systems involves the growth, merger and interaction of those meso-β convective feature located nearest the intersection of the meso-α axes along which they are aligned. Throughout the mature phase of the MCC, multiple meso-β convective components may persist within the more uniform meso-α cloud shield as expanding regions of stratiform anvil precipitation develop. The decay of the system is marked by the weakening and difluent propagation of its meso-β convective components. Hourly precipitation data reveal a characteristic precipitation life-cycle in relation to the MCC's satellite appearance. These typical meso-β-scale characteristics offer potential tools for the short-range forecasting of MCCs and their hydrological consequences.

Abstract

A variety of meso-β-scale (20–200 km, <6 h) temporal and spatial characteristics associated with the life-cycle of the meso-α-scale (200–2000 km, >6 h) convective complex (MCC) are described. The analysis is based on a typical episode of MCCs in the central United States. Thunderstorms in the MCC are generally well-organized into meso-β-scale convective features. The larger MCCs are typically preceded by several of these meso-β convective clusters or bands, which tend to be aligned along linear meso-α-scale features such as the eastern slope of the Rockies or thermodynamic discontinuities evident in hourly surface or satellite data. The intense development of these larger systems involves the growth, merger and interaction of those meso-β convective feature located nearest the intersection of the meso-α axes along which they are aligned. Throughout the mature phase of the MCC, multiple meso-β convective components may persist within the more uniform meso-α cloud shield as expanding regions of stratiform anvil precipitation develop. The decay of the system is marked by the weakening and difluent propagation of its meso-β convective components. Hourly precipitation data reveal a characteristic precipitation life-cycle in relation to the MCC's satellite appearance. These typical meso-β-scale characteristics offer potential tools for the short-range forecasting of MCCs and their hydrological consequences.

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