May 22 - July 28
The Public’s Prioritization of Probability and Intensity in Tornado Risks
Jada Lamar, Joesph T. Ripberger, and Harold E. Brooks
What is already known:
- The SPC convective outlook includes a combination of categorical and probabilistic forecast information but currently prioritizes probability information.
- The SPC is considering adding more explicit intensity information to the outlook to evaluate how it will affect user comprehension.
What this study adds:
- Most people consider probability and intensity information to be equal in importance.
- The majority of the public uses probability and intensity information interchangeably or synergistically when thinking about a tornado risk.
- Probability information is used more frequently by the public when interpreting categorical risk words.
Abstract:
Historically, the Storm Prediction Center (SPC) has utilized both categorical risk and probabilistic information in their convective outlooks. The categorical risk information is based almost exclusively on the probability of storms with little or no attention to their intensity. The SPC has considered adding more explicit intensity information to their outlooks but there is limited research on how people define a risk using probability and intensity information. Our goal is to help the SPC determine if the addition of intensity information would improve the effectiveness of the convective outlook. In this study, we use survey data derived from the 2017 and 2019 Severe Weather and Society Surveys (WX17 and WX19) to evaluate how members of the public weigh probability and intensity information during severe weather events. Results from this study indicate that most members of the public use both types of information equally, even collaboratively, to make decisions. Our findings suggest that adding more explicit intensity information to the convective outlook may improve public assessment of tornado risk.