Large-Scale Patterns Associated with Severe Summertime Thunderstorms over Central Arizona

Abstract

Abstract Severe thunderstorms are relatively rare over Arizona and occur most frequently during the summer monsoon period, that is, July, August, and early September. Forecasting in Arizona during the summertime is quite difficult and skill scores are low for both precipitation and severe thunderstorm watches and warnings. In the past, due to the sparse population of Arizona, severe thunderstorms usually impacted few people and were considered relatively insignificant events. However, over the last 20 years, the population of central Arizona has grown dramatically, and the impact of severe thunderstorm and flash flood occurrences has also increased. Synoptic conditions associated with 27 severe thunderstorm events that occurred in central Arizona during the summer monsoon have been examined systematically and compared to long-term mean July conditions. The period of study covered 1978 to 1990, and cases selected were limited to the high population area of central Arizona. McCollum subjectively identified ...