8–10-Day Ensemble Forecast Products: An Assessment of User Needs, Preferences, and Impacts on Decision-Making

The Weather Prediction Center (WPC) provides weather forecast information on hydrometeorological conditions in the range from one to seven days. In response to an increase in user demand for longer-range forecasts, as well as the increased accuracy of longer-range model guidance, WPC has begun to explore prototype products to communicate forecasts for precipitation and temperature at the 8-10-day range. These 8-10-day forecasts are guided by ensemble prediction systems and result in probabilistic forecasts that can express a range of probabilities for temperature and precipitation outcomes.

Probabilistic forecast information in this range can be useful for decision-making for a wide range of users and also presents new challenges and questions surrounding the best ways to format and display information for multiple audiences. To better understand the decisions these forecasts may support, and to help inform the testing and creation of the prototypes, a study was undertaken that identified key users of WPC forecast products and the critical decisions they make that could be supported by these prototype forecasts. The findings informed the design of several 8-10-day products to enhance the ability of users to understand and incorporate information into their decision-making. The study sought to answer questions relating to 1) how probabilistic forecasts in the 8-10 day timeframe improve decision-making by core partners, 2) the appropriate manner to communicate potential hazards through the use of probabilistic forecasts, 3) which forecasts improve core partners’ ability to distinguish between low impact and high impact events, and 4) whether there is an optimal mix of visualizations, stories, colors, etc. that best conveys information to improve decision support. Two rounds of focus groups with key users were undertaken, with the first testing WPC prototype products and the second testing revisions to those products based on input from the first round. Feedback from both rounds of focus groups indicates that changes to the design and presentation of the products are needed to facilitate understanding and utility. The revisions that were undertaken following the first round of focus groups addressed concerns about use of language, labeling, ability to select thresholds, and visual presentation of data sets. Recommendations for additional revisions followed the second round. This presentation will highlight the findings related to product revisions as well as the perceived utility of the information conveyed.