Toward Understanding Future Changes in the Tornado and Severe Hail Landscapes of Eastern Colorado

Eastern Colorado is a unique area over which to explore future changes in severe weather phenomena. Not only is this region a hot spot for tornadoes, it also boasts one of the fastest-growing metropolitan areas in the country. Undoubtedly, impacts on tornado frequency and intensity due to both climate change and population dynamics will play a role in determining how many people may be at risk from this hazard in the future, defined in this study as the year 2100. From a meteorological perspective, future environments are expected to be more conducive to severe weather, owing in part to increased low-level moisture, increased CAPE, and increased CIN leading to the potential for more explosive convection. However, more favorable environments would only imply more severe weather if those environments can be realized. To determine a realistic change in future tornado events across eastern Colorado (i.e., east of 105.3°W), this study computes average tornado environments using the Storm Prediction Center’s Storm Mode data base, and projects future changes using high-resolution convection-allowing downscaled simulations of tornado events under a control and pseudo-global warming (PGW) scenario. In addition, synthetic tornado reports are computed for a current and future climate across the domain using thresholds of various severe weather parameters, such as updraft helicity and upward vertical velocity, again derived from dynamically-downscaled high-resolution simulations. Future population trends can be computed in a variety of ways, based on a plethora of population dynamics factors. In this study, realistic population projections across eastern Colorado for the year 2100 are made using data from both the Integrated Climate Land-Use Scenarios (ICLUS) version 1 and a data set developed at NCAR. These two sets of projections use different methodologies, with the former using the Special Report on Emissions Scenarios (SRES) and the latter utilizing the more recent Shared Socio-economic Pathways (SSPs), both of which contain multiple scenarios forced by differences in how population dynamics factors are expected to change. Thus, comparison between these two data sets is made to ascertain the differences they produce in risk from tornadoes. With these projected changes in both meteorology and population, this study aims to find their relative contributions to the future human risk from tornadoes using the Tornado Monte Carlo (TorMC) model developed and described in Strader et al. (2016). The resulting outlooks of future tornado risk across eastern Colorado can be of great worth to professional sectors such as insurance, local and state government, city planning, emergency management, and meteorology, as resource allocation, insurance policies, and capital building projects could all be modified based on the projected future risk. In addition, increasing public awareness of the changing risk landscape is important to guide decision making and mitigate negative impacts from tornadoes.