Impact-Based Tornado Warnings: An Experimental Investigation of Shelter in Place Intentions

The NWS recently implemented nation-wide enhanced tornado warnings known as Impact-Based Warnings (IBWs). The overarching goal of these IBWs is to improve the threat warning process and motivate appropriate and effective responses to reduce risk. IBWs include enhanced language about a tornado’s potential impact and severity, including potential consequences. Research recently published by the author in Weather, Climate, and Societycompared behavioral intentions to shelter in place made to IBWs vs. the older, non-IBWs. In that research, undergraduates adopted the role of a plant manager and read both IBW and non-IBW warnings. At three different decision points, participants made decisions about having the plant shut down and having employees shelter in place. The results showed that the IBW warnings produced higher likelihood ratings of sheltering in place, but only after the additional IBW information was presented, supporting the effectiveness of the IBW approach.

The current research presented here expands upon that previous work in a number of ways. First, participants made shelter in place decisions to tornadoes of potentially greater magnitude (EF3-EF4). These IBWs also included either the “CONSIDERABLE” or “CATASTROPHIC” threat tag (threat tags were not included in the earlier research). Second, the participants were much more diverse with respect to a variety of demographic variables having been recruited through a nationwide pool. Third, a new control condition was included such that some warnings matched the IBWs in terms of word length, but these longer warnings did not include the use of “scary” language. These longer control warnings were used in order to rule out simple increased warning length as a factor contributing to the higher shelter in place decisions made to the IBWs. With these changes in place, the experiment’s methodology was identical to that used previously – participants read the tornado warnings and at three different decision points, using a 0-100 likelihood scale, made decisions about having the manufacturing plant shut down and employees shelter in place. Results will be compared to those obtained previously and discussed within the context of NWS best practices.