Toward a New Warning Method of Threats-in-Motion: Improving Warning Lead and Departure Times with Innovative Hazard Communication and Dissemination Techniques

Currently, National Weather Service (NWS) severe thunderstorm and tornado warnings are issued as polygons that cover a two-dimensional area of expected or known threat, matching severe weather criteria, within a time period from 30 to 60 minutes. If a thunderstorm remains severe, new warnings are issued separately, downstream of previous warnings. These new warnings are usually issued in “stepwise” fashion until the threat has ended or has dropped below severe criteria. This results in inequitable lead times for locations downstream from the threats. Locations at the far end of the initial warning typically receive much more lead time than locations at the near end of subsequent warnings. Departure times, the times at which locations are removed from warnings, are also inequitable and locations on the near end of the initial warning could remain under a warning well after the threat has passed.

Threats-In-Motion (TIM) is a proposed method for future warning processes that provides more equitable lead and departure times for all locations downstream of a hazard. TIM polygons follow hazards and are continuously updated every minute. Locations are automatically removed from warnings once the threats have passed. Significantly increased equitable lead times and reduced departure times have been demonstrated on several notable severe and tornadic events. Additional considerations that must be addressed, such as effective and timely threat communication and partnering emergency alert services, will be explored through this effort.

A workshop, conducted in August 2019, aimed at developing and exploring pathways for potential implementation of TIM in the NWS warning paradigm. Researchers, policymakers, and end-user communities gathered to establish a framework and guidelines for the TIM method, including working within the boundaries of current and potential future dissemination technologies. This workshop was the first step toward the adoption of concepts from within the Forecasting a Continuum of Environmental Threats (FACETs) paradigm. Outcomes of this workshop will be presented.