A climatological analysis of antecedent drought and spring tornadic activity

The Intergovernmental Panel on Climate Change (IPCC) has indicated the probability of an increase in extreme events and acceleration of the water cycle due to climate change. Land surface soil moisture is part of the water cycle and has a direct effect on the atmosphere through moisture and energy exchanges. The lack of sufficient antecedent soil moisture has been hypothesized to reduce convective development and tornadoes in the spring (Shepherd et al. 2009), possibly through soil memory and subsequent atmospheric response. The Southeastern United States experienced deadly tornado outbreaks during drought conditions (e.g. the 14 March 2008 Atlanta tornado), and it is the intent of this study to investigate the relationship, if any, between Southeastern tornadoes and drought. We will present preliminary findings on our NASA-funded research to (1) quantify the frequency of occurrence of tornado activity under antecedent (1-month, 2-month, and 6-month) drought conditions, (2) understand how drought affects atmospheric stability in terms of Convective Available Potential Energy (CAPE) and Convective Inhibition (CIN), and (3) determine if occurrences of drought are related to the Bermuda High Index (BHI).