The Evolution of the Mesoscale Environment of Severe Local Storms: Preliminary Modeling Results

Richard A. Anthes National Center for Atmospheric Research, Boulder, CO 80307

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Ying-Hwa Kuo The Pennsylvania State University, University Park 16802

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Stanley G. Benjamin The Pennsylvania State University, University Park 16802

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Yu-Fang Li Department of Geography, Hang-zhou University, People's Republic of China

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Abstract

The development of mesoscale features in numerical model forecasts of the environment of severe local storms is examined for two of the SESAME-1979 cases. The results show that a 10-layer model with a horizontal resolution of about 100 km, simple physics and initialized with essentially synoptic-scale data, is capable of generating and maintaining mesoscale phenomena in the 0–24 h time period. These results indicate that some mesoscale phenomena are predictable for periods of time longer than the lifetime of the mesoscale feature itself. Mesoscale features produced in the forecasts of the 10–11 April and 25–26 April cases include low-level jets, mesoscale convective complexes, upper-level jet streaks, cold and warm frontogenesis, drylines, mountain waves and capping inversions (lids). The development and structure of these phenomena in the model forecast are examined in detail and the interactions among the phenomena are emphasized. The results strongly confirm the conclusions from earlier studies that improved forecasts of mesoscale weather systems are possible through the use of fine-mesh models. Improved results can be expected with the incorporation of better surface and boundary-layer physics and with the use of mesoscale observations in the initial conditions.

Abstract

The development of mesoscale features in numerical model forecasts of the environment of severe local storms is examined for two of the SESAME-1979 cases. The results show that a 10-layer model with a horizontal resolution of about 100 km, simple physics and initialized with essentially synoptic-scale data, is capable of generating and maintaining mesoscale phenomena in the 0–24 h time period. These results indicate that some mesoscale phenomena are predictable for periods of time longer than the lifetime of the mesoscale feature itself. Mesoscale features produced in the forecasts of the 10–11 April and 25–26 April cases include low-level jets, mesoscale convective complexes, upper-level jet streaks, cold and warm frontogenesis, drylines, mountain waves and capping inversions (lids). The development and structure of these phenomena in the model forecast are examined in detail and the interactions among the phenomena are emphasized. The results strongly confirm the conclusions from earlier studies that improved forecasts of mesoscale weather systems are possible through the use of fine-mesh models. Improved results can be expected with the incorporation of better surface and boundary-layer physics and with the use of mesoscale observations in the initial conditions.

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