Inter- and Intra- Seasonal Variability of Summer Thunderstorms determined by the ANOVA

Data developed for a study of convective initiation patterns and behaviors in the northern Mid-Atlantic region were examined with regard to intra- and inter- annual variability through the ANOVA. The intent was to determine if significant differences existed between and/or among the frequencies of “Event” days versus “Contaminate” and “Null” occurrences of thunderstorms during the summer season. These were also compared with the occurrence of “Severe” cases falling on “Event” versus “Contaminate” days. The data were considered with regard to time of the season, year-to-year variability, and how these varied according to both the synoptic flow at 500 mb and the surface synoptic weather pattern. Results indicated clear variations that could be used to diagnose the expected nature, behavior, and general frequencies of thunderstorm activity for a given summer season or month and that would be useful climate indicators for planning purposes and similar applications.