Climatic characteristics of summer season severe weather

As part of a study on convective initiation modes in the northern Mid-Atlantic region during the summer, the occurrence and distribution of severe storms was considered according to the type of day and prevailing synoptic patterns. Nine summer seasons of local storm data were gathered (2000-2008) based for the PHI and OKX National Weather Service offices CWA and the immediate surrounding area. The occurrence of severe weather reports was examined with regard to location, frequency, and timing as related to initial convective development on the day severe weather took place. These were then mapped in order to offer a composite image of any preferred points of origin and/or tendencies as a function of 500 mb flow and surface synoptic features and patterns. These were also compared to population and other datasets to determine whether any reporting biases may have been present. Preliminary findings suggested that the majority of severe weather occur in June while August had the least. Severe weather occurred most frequently under a southwest flow aloft but severe weather during northwest and westerly flows was not uncommon. Cold fronts were associated with the majority of severe weather days (and reports). During the period of study the number of severe occurrences increased, with 2008 having the most days (34) of severe weather observed. The most common severe weather type to affect the area was strong and damaging winds. Tornado reports were not common, but when they did occur they were nearly equally associated with cold fronts and stationary fronts.