The Impact of the Warn-on-Forecast System in the "Watch-to-Warning" Period

The development of probabilistic forecast guidance, which could enable forecasters to communicate high-impact weather information to a broad range of end-users in the “Watch-to-Warning” period, is a scientific and societal challenge that is a current focus of severe weather research. NOAA is exploring new methods to provide probabilistic hazard information, including the use of an experimental storm-scale ensemble known as the Warn-on-Forecast System (WoFS). This ensemble generates rapid updates and probabilistic predictions of individual thunderstorms, which is essential for communicating the most likely path, intensity, and timing of severe weather events such as tornadoes, hail, winds, and flash floods at lead times of minutes to a few hours. The use of WoFS has been shown to impact the language used in nowcasts and public-facing graphics from local NWS offices for different hazards. In the past, this timeframe was characterized by a dearth of probabilistic numerical guidance and limited forecast specificity on the timing and intensity of severe weather. However, local NWS offices demonstrated that WoFS can help them fill this gap, resulting in the delivery of more precise information with greater lead time to decision-makers and NWS core partners. We will explore how WoFS has positively impacted communication strategies during the watch-to-warning period by highlighting real-time, real-world NWS offices' usage. We will showcase how this messaging has led to the creation of more specific information, additional public-facing graphics, and longer lead times provided to various partners, such as emergency managers (EMs) and broadcast meteorologists. Research with end-users has mainly concentrated on local NWS offices and EMs; future research will expand to the broadcast community to explore the impacts probabilistic information may have on their communication strategies.