Update on Threats-In-Motion for Severe Storm Warnings - 2024 Edition

Threats-In-Motion (TIM) is a proposed warning decision and dissemination approach that aims to enable the National Weather Service (NWS) to upgrade severe thunderstorm and tornado warnings from the current static polygon system to continuously updating warning polygons that move with the storm. TIM has the potential to improve average warning lead time and provide more equitable (uniform) lead times for those in the path of long-tracked severe storms.

TIM will contribute to the NWS initiative for community-centric warnings. This involves adding the capability to communicate, at the sub-county/zone level, new areas being impacted by a hazard (receiving a new warning alert), areas still being impacted by a hazard (no additional alerts), and areas no longer being impacted by a hazard (receiving an all-clear alert). Additionally, several techniques have been developed to mitigate the re-warning of locations when a warning polygon’s motion is repeatedly re-adjusted.

This presentation will offer an update on the progress of TIM software development and recent experiments conducted at the NOAA Hazardous Weather Testbed (HWT). If TIM receives approval through the NWS governance process, the transition to operations is expected to occur in two phases. The first phase, known as “Tiny TIM,” would introduce the capability to extend warnings in time and area. This means that long-tracked storms would not need to be re-warned along their path. The second phase, referred to as “Taller TIM,” automatically fills in the periods between warning extensions with one-minute updates. Taller TIM has the potential to provide an even greater improvement in average lead time and lead time equitability.