Frequencies of Cyclones and Cyclogenesis for North America, 1951–1970

Abstract

The mean frequency of cyclonic events for North America is determined for five months based on the 20-year period, 1951?1970. Monthly maps are used to present the data and display the distribution of cyclonic frequencies. The frequencies of cyclogenesis are also determined and used to construct mean cyclone tracks. A subjective comparison between these data and cyclone frequencies from earlier studies reveals differences which do not appear to form a consistent pattern. Although some differences can be attributed to differences in the methods of analysis, others suggest significant variation between these years and the early 1900's.