Major Risks, Uncertain Outcomes: Making Ensemble Forecasts Work for Multiple Audiences

Effective communication of weather and hydrologic forecasts is critical to protect life and property during severe events, especially those that result in flooding.  Residents, emergency managers, and community and water resource managers need to make timely decisions about how and when to prepare.  There is increasing recognition in the forecast community that the National Weather Service shares a responsibility to forecast weather, and communicate that information as clearly as possible, including how to prioritize risk and what action is needed given the likelihood of the forecast and forecast confidence. Specifically, understanding uncertainty in a forecast as communicated through ensemble forecast products is necessary, however it is these uncertainty products (such as the Meteorological Model Ensemble River Forecasts or MMEFS) that can often create the most confusion for non-scientists.

Building on previous research, this project investigates the Hydrologic Ensemble Forecast System (HEFS), a national system that provides short and long-range forecasts, ranging from 6 hours to 1 year, and operates similarly to the MMEFS used in the Eastern Region.  To study the utility of the HEFS products, the barriers to proper understanding of the products, and any modifications in product design that could improve the understandability and accessibility for residential, emergency managers, and water resource managers, two rounds of focus groups were planned in the Sterling, VA Weather Forecast Office (WFO) County Warning Area, working with the both the WFO and the Middle Atlantic River Forecast Center.  Using weather scenarios that were developed using a variety of flood forecast products including various HEFS representations, the first round of focus groups was held in the fall of 2016, with the results leading to 1) better understanding of the potential of HEFS as a decision-making tool and 2) product revisions that will be tested in the second round in the spring of 2017.  

HEFS has not yet been publicly released.  It is anticipated that including this research on the front end of product deployment will improve efficiency by providing a new product that is well received and in less need of future revision due to communication barriers.  By testing with actual potential users, the product will have improved familiarity upon release and will help NWS to anticipate what additional instruction may be required for users of the product.  The study is also anticipated to provide the research community and weather enterprise with further insight to the barriers audiences face in understanding uncertainty forecasts.