During May and June of 2015, the Southern Great Plains (SGP) of the United States experienced numerous heavy rainfall and flooding events. The immense amount of rainfall (in excess of 80 cm) over a short period had tremendous impacts on the water resources of the region, marked the end of prolonged drought, and culminated into a flash pluvial. Flash pluvials, similar to flash drought, are a short-term period of rapid transition into wetter than average conditions. Flash pluvials are marked by widespread, heavy rainfall within a region. This rainfall can lead to a regional replenishment of water resources and soil moisture, particularly in the case of 2015. The investigation of this case seeks to determine the causation of this anomalous precipitation event.

The goal of this study was to examine the traits and causes of the excessive precipitation over the SGP in May and June of 2015 including synoptic characteristics, the role of moisture transport, and the impact of Tropical Depression Bill. This was accomplished by statistically analyzing the daily precipitation with the most significant precipitation events of the flash pluvial selected for additional analysis. These cases were composited to quantify atmospheric patterns and moisture transport via Atmospheric River (AR) analysis and integrated vapor transport (IVT) to diagnose the source of moisture that led to the extreme precipitation events.

The key results included seeing an above normal number of synoptic wave events, with strong upper level low pressure systems present for the significant precipitation events. This increased wave activity combined with enhanced moisture transport from the Gulf of Mexico was a defining feature of the flash pluvial event. The interaction of the features observed in this analysis are what led to this event being highly significant. Additional features that led to the flash pluvial experiencing extreme precipitation include frequently linear storm mode and high precipitation efficiency, leading to record-breaking precipitation across the SGP. The interaction of these features at varying time scales contributed to the SGP experiencing extreme precipitation, and by examining these features we can better understand the causation of flash pluvials and other extreme precipitation events.