An empirical assessment of impact based tornado warnings on shelter in place decisions

In the spring of 2012, the United States' National Weather Service implemented new impact based tornado warnings (IBWs) that include information about predicted storm impacts to improve the likelihood of one taking protective action. In addition to including more extreme language, IBWs for especially intense tornadoes include threat tags labeling the impact as “considerable” or “catastrophic.” Research by the author Casteel (2016) [3] showed that, when compared to non-IBWs, IBWs for low intensity tornadoes produced higher intentions of sheltering in place. The research reported here builds upon that earlier work. In four experiments, IBWs for stronger tornadoes are compared to those for weaker tornadoes, to assess whether the severe language used in the higher impact IBWs motivates higher sheltering intentions. Participants adopted the role of a plant manager tasked with keeping employees safe and read IBWs containing differing impact and severity language. At three decision points, the participants stated their likelihood of having employees shelter in place. In three of four experiments, the results show that any warning containing impact language stronger than a low intensity IBW, regardless of the presence of threat tags or extreme language, produced higher sheltering intentions. Additionally, sheltering decisions to “considerable” or “catastrophic” warnings did not differ in two experiments involving adult samples. These results suggest that the heightened risk transmitted by the stronger impact statements does communicate increased risk and that extreme language is not necessary to craft an effective tornado warning.