A Spatiotemporal Perspective on the 31 May 2013 Tornado Evacuation in the Oklahoma City Metropolitan Area

Abstract

Abstract On 31 May 2013, an extremely large and violent tornado hit near the town of El Reno, Oklahoma, a small town in the Oklahoma City metropolitan area. The size and intensity of this tornado, coupled with the fact that it was heading toward Oklahoma City, prompted local broadcasters to warn residents to evacuate their homes and head south if they could not shelter belowground. This warning led to a large-scale evacuation of the metropolitan area and massive traffic jams on the interstates and major highways that could have caused casualties in the hundreds if the tornado had not dissipated before reaching Oklahoma City. The focus of this study was to understand the magnitude of the 31 May 2013 evacuation through the evaluation of traffic volume data and to determine how frequently such evacuations occur in Oklahoma City and other metropolitan areas. We found that of the six metropolitan areas tested, only Oklahoma City had mass anomalous traffic reversal (ATR) days (days with a mass evacuation signal) with 31 May 2013 having the largest mass ATR day by far. Despite the rarity of mass ATR days, the potential consequences of a large, violent tornado hitting gridlocked traffic is significant, and we recommend that communicators encourage more local sheltering options. Significance Statement On the evening of 31 May 2013, a large-scale evacuation of the Oklahoma City metropolitan area occurred as a result of a very large and dangerous tornado that had formed near the town of El Reno and was moving east toward Oklahoma City. If the tornado had not dissipated before it reached the city it could have caused hundreds of casualties as it passed over gridlocked roads. We sought to understand the frequency of such mass evacuations and found that no other event in six metropolitan areas studied during 2011–18 could compare. While such evacuations fortunately appear rare, more work should be done to understand why they happen when they do and to connect individuals with better local sheltering options.