A Decision Arc Framework to Facilitate Tornado Threat Awareness and Protective Behaviors

There is considerable interest in and progress on development of customizable, user-centric notifications and decision aids to complement existing public warning and alerts systems for weather hazards. If carefully constructed and calibrated, alerts tailored to specific people, locations, and situations can enhance situational awareness and facilitate timely and effective protective behaviors. Such decision-support systems can be helpful for users who require more than usual lead time to monitor trends, begin preparations, and implement a protective plan. This research builds from recent and ongoing research in decision aids for wildfire evacuation and sheltering, as well as meteorological and geographical approaches to modeling and communication of uncertainty for severe convective hazards.

Here, we demonstrate a version of the trigger buffer and decision arc methodology, adapted from wildfire evacuation modeling to the tornado context. As currently conceptualized, the framework complements and facilitates use of the existing National Weather Service watch and warning system by assisting users to set heuristic spatiotemporal thresholds to match the timing needed for various household- or facility-specific preparedness and response behaviors. While the framework can theoretically fit a range of user-defined time horizons, this work focuses on 15-minute intervals between 15 and 60 minutes prior to arrival of a tornado threat. We show preliminary results for how the decision arc framework could operate using tornado case studies from recent high-impact tornadoes that occurred in situations of enhanced vulnerability such as late at night and/or those that moved at faster translational speeds (e.g., Cookeville, TN, 3 Mar 2020, EF4 tornado). These case studies also illuminate useful directions for future work to continue development of the decision arc framework for effective user-centric leverage of NWS convective watch and warning products for timely protective behaviors.