SPATIAL, SYNOPTIC, AND SEASONAL PATTERNS OF HEAVY RAINFALL IN THE SOUTHEASTERN UNITED-STATES

This paper examines the synoptic climatology and seasonality of heavy rainfall across the southeastern United States. Frontal systems (parti cularly cold fronts) were found to be the dominant mechanism that indu ces heavy rainfall across the study area, but tropical disturbances an d air-mass storms also contribute, especially at the more coastal loca tions. Annual regimes were found to vary dramatically from one site to another, and seven of the eight sites investigated exhibited statisti cally significant seasonality. Generally, peaks in heavy rainfall are bimodal in the western portion of the region, occurring in the transit ional seasons. The central portion of the region peaks in late winter and spring, whereas the area east of the Appalachians (including Flori da) has summer peaks. This spatial pattern is likely related to patter ns of mid-tropospheric air flow and positions of the Bermuda High in s ummer, and the seasonality of cyclogenesis in North America.