Observed and Forecast Changes In United States Tornado Exposure

This research examines how tornado risk and societal exposure interact to create tornado disaster potential in the United States. Fine-scale historical and forecast demographic data are used in a set of region-specific, Monte Carlo tornado simulations to reveal how societal development has shaped, and will continue to shape, tornado disaster frequency and consequences. Results illustrate that, although the U.S. Midwest contains the greatest built-environment exposure and the Central Plains experiences the most significant tornadoes, the Mid-South contains the greatest tornado disaster potential. This finding is attributed to the relatively elevated tornado risk and accelerated growth in developed land area that characterizes the Mid-South region. Disaster potential is forecast to amplify in the United States due to increasing built-environment development and its spatial footprint in at-risk regions. In the four regions examined, both average annual tornado impacts and associated impact variability are projected to be as much as 6 to 36 times greater in 2100 than 1940. Extreme annual tornado impacts for all at-risk regions are also projected to nearly double during the 21st century, signifying the potential for greater tornado disaster potential in the future. The key lesson is that it is the juxtaposition of both risk and societal exposure that drive disaster potential. Mitigation efforts should evaluate changes tornado hazard risk and societal exposure in light of land use planning, building codes, and warning dissemination strategies in order to reduce the effects of tornadoes and other environmental hazards.