A Tornado Watch Scale to Improve Public Safety

A tornado refuge rubric was revised into a six-level, hierarchical Tornado Watch Scale (TWS) from level 0 to level 5 based on the likelihood of high or low-impact tornadic events. Levels correspond to an estimate of the maximum potential tornado intensity for a given day and include refuge/shelter categories of “Adequate,” “Questionable” or “Inadequate,” which encompass a range of refuge/shelter locations taken from the enhanced Fujita scale. Ratings are based on a conservative estimate of damage indicators in high winds and the safety of a person taking refuge inside buildings of varying structural integrity. Audio recordings similar to those used in current NOAA weather radio communications were developed for each TWS intensity level. Recordings representing an existing tornado watch, existing particularly dangerous situation (PDS) tornado watch, and three proposed levels from the TWS were then used in interviews with Alabama residents to determine how changes to the information contained in the watch statements would affect each participant's tornado safety actions and risk perception. Participants were also questioned about their knowledge and past experience with tornado hazards, and their preference between the existing NWS tornado watches and the TWS. Results indicate a strong preference for the TWS when compared to existing products. The TWS was favored for providing additional information, containing descriptions of expected severity, and being easy to understand. The TWS also elicits more adequate safety decisions and more appropriate risk perception when compared to existing products, and these increases in safety were statistically significant. Although the TWS was initially proposed as a scale with discrete levels, recent research has begun to evaluate comprehension and efficacy of the TWS with confidence intervals or uncertainty ranges that can possibly overlap with the TWS levels.