Mesoscale and Synoptic Analysis of the Southern Great Plains 2015 Flash Pluvial

In May and June of 2015, numerous heavy rainfall and flooding events occurred in the United States Southern Great Plains. The immense amount of rainfall over a short time had a tremendous impact on the moisture balance of the region. These events marked the end of a drought in the Southern Great Plains, and quickly transitioned the region into a period of excessive precipitation, called a flash pluvial. Flash pluvials, similar to flash drought, are a short-term period of rapid transition into wetter than average conditions, marked by widespread, heavy rainfall which leads to a regional replenishment of water resources and soil moisture.

This flash pluvial case study identifies characteristics and causes of the excessive precipitation over the Southern Great Plains during May and June of 2015. Data from the North American Regional Reanalysis (NARR) supplemented by Oklahoma Mesonet data will be used to investigate environmental conditions and features that forced the repeated storm initiation such as the low level jet. This study uses composites of NARR data to identify atmospheric features unique to this case and to analyze the individual rainfall events and differing storm modes that contributed to excess precipitation over the region. These include mesoscale convective systems and the passage of Tropical Depression Bill over the region.

Flash pluvials bring significant rainfall repeatedly to the same region, providing drought relief and causing dangerous flooding events. These agricultural, hydrologic, and socioeconomic impacts over such short timescales warrant an improved understanding of the defining atmospheric conditions which precede and accompany flash pluvials. Understanding the cause of these events will improve seasonal to subseasonal forecasting, improve public preparedness, and provide critical information to agricultural stakeholders and water resource managers.