Evaluating the Effectiveness of a Tornado Watch Scale Using Uncertainty

Highly destructive events cause us to reconsider the efficacy of risk communication in the tornado watch and warning process. With numerous fatalities resulting from violent tornadoes in just the last four years (Tuscaloosa 2011, Joplin 2011, Washington, IL 2012, Van Buren, AR 2012, Moore 2013, El Reno 2013) and millions of dollars in property destruction (Hattiesburg 2013), it is time to evaluate the possibility of enhancing the way we alert people about the potential for a tornado outbreak. Much of the current focus and funding in tornado risk communication is on improving warning lead times and the warn-on forecast system. While these projects address important concerns, there could be considerable improvement in risk communication during the 24-hour period prior to a potential tornado outbreak incorporating basic principles of risk levels for tornado outbreaks and creating a platform by which risk is more effectively communicated to consumers prior to tornado warnings. This would permit a reasonable estimate of the threat people potentially face from an impending tornado outbreak and would provide them safety actions based on the potential intensity of tornadoes for a given day. Based on a system of rating tornado shelter/refuge adequacy depending on the potential intensity of the event, the focus of this paper is the evaluation of a tornado watch communication product called the Tornado Watch Scale (TWS) (2015). The TWS was initially created with six levels (0 -5) with discrete categories. Results indicated a strong preference for the TWS when compared to existing products because it provided additional information, contains descriptions of expected severity, and is easy to understand. The TWS also elicits more adequate safety decisions and more appropriate risk perception when compared to existing products. Although the TWS was initially proposed as a scale with discrete categories, the focus of this research is to evaluate comprehension and efficacy of the TWS with confidence intervals or uncertainty ranges that can possibly overlap with the TWS levels. Phase 1 of this study included workshops with NWS and EMA personnel to gather feedback on how the TWS would be used with uncertainty ranges, or other modifications at the requests of EMA and NWS personnel. Phase 2 involved a series of focus groups of the public in Alabama where the TWS was evaluated with new suggestions and modifications from phase 1. The combined results of phase 1 and phase 2 identified gaps in our current understanding of the transfer of scientific knowledge from forecaster to consumer while providing a foundation for future investigation. These results support a continued emphasis on evaluating ways to improve severe weather communication to enhance risk perception.