Design and Integration of Probabilities for Hazard Information in Hazard Services to Operationalize FACETs Concepts

Forecasting a Continuum of Environmental Threats (FACETs) is a proposed next-generation severe weather watch and warning framework that is modern, flexible, and designed to communicate clear and simple hazardous weather information to serve the public. One of the underlying aspects of FACETs is rapidly-updating probabilistic hazard grids, known as Probabilistic Hazard Information (PHI). PHI can be used to provide custom user-specific products that can be tailored to adapt to a variety of needs – for example, providing longer lead times, at lower confidence, for more vulnerable populations with a lower tolerance for risk.

The NOAA/National Severe Storms Laboratory (NSSL) has developed a prototype PHI tool which allows forecasters to integrate probabilistic guidance and their own interpretations of the atmosphere to issue PHI for severe convective hazards - hail, wind, and tornadoes. The NOAA/Earth System Research Lab's Global Systems Division has integrated the PHI tool and concept into the NWS Advanced Weather Information Processing System (AWIPS) Hazard Services software to include the capabilities for forecasters to provide PHI at the 0-2 hour “warning” scale. As additional functionality and capabilities of PHI are built into the Hazard Services framework, and as these concepts move closer to becoming operational in the NWS, several challenges have been identified. For example, generating a continuous, probabilistic grid across the Storm Prediction Center (SPC) convective outlook and Weather Forecast Office (WFO) scales becomes difficult. This difficulty stems from considering the meaning of hazard probabilities and what kind of value they represent both from mathematical and end-user/public viewpoints. In addition, the concept of non-conditional versus conditional probabilities must be considered, as well as the potential inclusion of severity thresholds, update frequency and forecaster confidence. To bring context to these concepts and the probabilistic values, the application of reference classes can be used to achieve a working grid and design. As this conceptual groundwork is formulated and fine-tuned by many stakeholders, a framework for legacy VTEC output for the next generation of probabilistic watches and warnings can be developed for Hazard Services. An initial task aimed at achieving this design concept involves the integration of NSSL’s Cloud to Ground (CG) Lightning Probability algorithm. Exploratory concepts for lightning output designs are presented. Moving forward, these output designs could eventually serve as a starting point for other hazards such as severe and tornado.