Predicting the Climatology of Tornado Occurrences in North America with a Bayesian Hierarchical Modeling Framework
Journal of Climate
Climate change could conceivably shape tornado development of all types. Consideration of regional-specific tornado environment may better characterize the atmospheric condition favourable for tornadoes across different areas across North America. • This modeling tool that can be used to characterize the frequency of tornado occurrence in a particular location in North America, e.g., exceedance probability of more than 1 tornado within a selected period of the year. • The credibility of the
... dibility of the present probabilistic mapping relies on the strength of the association between "...the changes in the moments (central tendency, spread) of the distribution of the environments occurring in the course of a month/season to faithfully capture the changes in the frequency of extreme subdaily environments (tails of the same distribution) associated with tornado occurrence..." Destruction and fatalities from recent tornado outbreaks in North America have raised considerable concerns regarding their climatic and geographic variability. However, regional characterization of tornado activity in relation to large-scale climatic processes remains highly uncertain. Here, we develop a novel Bayesian hierarchical framework for elucidating the spatiotemporal variability of the factors underlying tornado occurrence in North America. We demonstrate that regional variability of tornado activity can be characterized using a hierarchical parameterization of convective available potential energy, storm relative helicity, and vertical wind shear quantities. We show that the spatial variability of tornado occurrence during the warm summer season can be explained by convective available potential energy and storm relative helicity alone, while vertical wind shear is clearly better at capturing the spatial variability of the cool season tornado activity. Our results suggest that the Bayesian hierarchical modeling approach is effective for understanding the regional tornado environment and in forming the basis for establishing tornado prognostic tools in North America.