When National Weather Service (NWS) forecasters wrestle with decisions about convective warnings, the pivotal moment often comes when radar and/or satellite imagery indicate that a threat, e.g. a tornado, large hail, strong winds, is imminent or already occurring. Prior to that moment, the available data may not instill enough confidence for the forecaster to pull the trigger on a warning. The Warn-on-Forecast System (WoFS) is designed to provide ensemble-based, probabilistic numerical guidance to increase forecaster confidence, and do so earlier in the decision-making process, so that warnings can be issued sooner.
WoFS is a revolutionary on-demand analysis and forecast system that may very well become the first UFS application to run operationally on cloud HPC. Although it is currently not part of the UFS, WoFS version 2 will work toward UFS integration by including the Model for Prediction Across Scales (MPAS) dycore and other UFS components, as well as adopting the Joint Effort for Data assimilation Integration (JEDI) framework. In the meantime, the NWS Office of Science and Technology Integration (OSTI) is leading a two-year WoFS demonstration project to explore the full value of this unique system for severe weather and beyond, and the option space for different implementation pathways.
WoFS has been under development at the NOAA National Severe Storms Lab (NSSL) since 2009, evaluated by NWS forecasters since 2017, and successfully demonstrated in a research environment as an on-demand, cloud-based prediction system since 2022. These real-time demonstrations have shown that WoFS can be particularly valuable in providing probabilistic guidance for individual thunderstorms, especially in the temporal gap between convective watches and warnings, as exemplified in this NSSL featured story. But it also shows promise in providing unique and useful guidance for local impacts from any rapidly evolving weather system.
Development efforts will continue at NSSL, in parallel with the new demonstration initiative spearheaded by OSTI. The broad goals of these joint efforts are to 1) build the knowledge and capability to support and leverage WoFS in the NWS, 2) strengthen relationships with the user community, 3) enhance utility of WoFS probabilistic guidance for a variety of rapidly evolving weather systems, 4) develop the concept of operations, and 5) build a next-generation, UFS-based WoFS system that is sufficiently robust for NWS operations.
For more information, please visit the NWS WoFS Demonstration Project and NSSL Warn-on-Forecast web pages, or contact the OSTI Modeling Program via their website.
