Convective Initiation in the northern Mid-Atlantic during the Summer Season

Convective initiation may display a variety of modes each day, from day to day, as well as within and between seasons. Both the occurrence and location of initiate cells are important to the ultimate coverage and characteristics of thunderstorm activity across the region. In order to better understand these features, a nine year data set was constructed to examine convective morphology as a function of boundary layer regime and synoptic pattern. Radar data for each of the summer seasons (June-July-August) was collected to identify and map initial convective activity and these were separated into Event, Contaminate, and Null days (all occurring between 1200 and 0000 UTC). Analyses focused on the frequency and distribution of convective type days as well as the variance from month to month, between synoptic types, and from season to season. Composite maps were generated to determine preferred regions for convective initiation according to synoptic patterns and as an aid to operational forecasters. The data were examined with regard to the NCAR re-analysis fields to distinguish key features that led to Event, Contaminate, and Null days as well as to help explain the distribution of the initial convective activity. Results indicated zones/areas of preferred activity, the relevance of terrain and physical features, and the impact of synoptic patterns as they interacted with these and mesoscale circulations.