What Makes a Tornado Deadly? An Updated Look Into the Factors Affecting Tornado Risk and Their Changes Over Time

Tornado risk extends beyond the simple probability of a tornado striking a location; it encompasses the likelihood that such an event will result in casualties and damage. There are three components to tornado risk: hazard, exposure, and vulnerability. The hazard is defined as the total track length of tornadoes, rather than just their touchdown points. Exposure is defined as the population within a certain distance from the tornado's track, which accounts for the stochastic nature of tornado paths. Vulnerability is characterized by the socioeconomic attributes of the population and physical landscape features, which can amplify tornado risk. In this study, we combine tornado track data with high-resolution population data and socioeconomic variables from the 2020 Census to assess the components of tornado risk across the eastern two-thirds of the United States from 1973 to 2022. We investigate how various factors, such as population density, poverty, race, age, and the prevalence of mobile homes, contribute to the likelihood of a tornado becoming deadly. We also explore the influence of tree density and building structures, as these elements can become lethal projectiles during a tornado. Lastly, changes in tornado risk over time are assessed by breaking the study period into two halves (1973-1997 and 1998-2022), which marks a period of significant improvements in tornado reporting and classification following the modernization of the National Weather Service. This temporal division allows us to explore how changes in data quality and reporting practices, as well as changes in population attributes, have influenced tornado risk and the lethality of tornadoes over the past half-century.