Rapid 500-mb cyclogenesis and anticyclogenesis

The process of intensification of 500-mb cyclones and anticyclones as represented in NMC's 500-mb analyses is investigated, using a sample of records for 500-mb cyclones and anticyclones drawn from the cool season of September 1983 through May 1984 to determine the statistically large intensification rates and thus to establish criteria for rapid intensification. From the catalog of all rapidly intensifying 500-mb cyclones and anticyclones defined by these criteria, seasonal and geographical frequency distributions of cyclogenesis and anticyclogenesis is constructed. It is shown that, for the data sample used in this analysis, the operational forecast models tend to underpredict rapid developments of 500-mb cyclones and anticyclones.