Southeast U.S. Flash Drought: Important research previously reviewed by Climate Impact Company and issued last May by Auburn University and ESRL/Boulder, Colo. identifies the presence of deep layer (10-200 CM) soil moisture deficit caused by the long-term climate accelerating a drought condition at surface level if dry conditions should emerge in the shallow layer (0-10 CM). This scenario developed mid-to-late summer in the Southeast U.S. and caused harsh drought to develop very quickly. The drought is rapidly becoming more intense and expanding to the far south/southeast Ohio Valley and Mid-Atlantic region. Rainfall deficits in this region is extreme generally near 10 in. to as much as 20 in. Rainfall is becoming desperately needed in these areas to slow the progression of drought.
As to the cause of this drought, research has yet to officially identify the catalyst. However, a likely contributor is the tendency for dry and warm-to-hot subtropical high pressure across vast areas of middle latitude warmer-than-normal oceans in recent years to cause deep layer soil moisture deficits while shallow surface moisture conditions may vary. Once dry conditions in the upper 10 CM soil depth emerges a flash drought emerges. The incidence of flash drought is increasing in North America and Europe likely related to the condition described. This condition also exists in the southern hemisphere middle latitudes and may be contributing to rapidly developing drought in Australia (which is ongoing) and at times parts of South America.