Collaborative Effort to Predict Hourly Temperatures during the August 21, 2017 Total Solar Eclipse in the Mid-Atlantic and Southeast (356)

Joshua Weiss, , ,



Joshua WeissNOAA/NWS Wilmington, NCJonathan Blaes and Gail HartfieldNOAA/NWS Raleigh, NCMeteorologists recognize that a solar eclipse can have a notable impact on the sensible weather in the regions in which they occur. These impacts can include a decrease in surface temperature, reduction and changes to surface winds, changes in cloud cover and more. Surprisingly, most operational numerical weather prediction systems do not account for the decrease in incoming solar radiation from the sun during an eclipse and the resultant changes in the weather. This is an issue as National Weather Service (NWS) forecasters provide high-spatial and temporal resolution forecasts of temperature, winds, and other fields that can be impacted by an eclipse and not captured by model guidance. NWS meteorologists in the Southeast and Mid-Atlantic worked collaboratively to account for some of these impacts in official NWS forecasts during the eclipse on August 21, 2017.With such a high profile event, consistency and accuracy among WFOs was very important. A Gridded Forecast Editor (GFE) smartTool and Procedure were locally developed and shared across several NWS local Weather Forecast Offices (WFO) to provide a more scientifically sound and consistent process for forecasters to adjust hourly temperatures for during the eclipse. An algorithm was developed to reduce the temperature forecasts based on historical temperature data from the 1970 total and 1984 annular eclipses in the southeastern U.S. by referencing the eclipse-based temperature drop to the average climatological diurnal temperature change. The GFE smartTool and Procedure incorporate several factors including the initial hourly forecast temperature and diurnal range without the eclipse impact, the amount of cloud cover, whether a location is in the total or partial eclipse region, and the algorithm adjustment. We will provide additional information on how the algorithm was developed and details on how it operates. A brief description of the weather pattern and sensible weather conditions during the time of the eclipse across the Southeast and mid-Atlantic will be shown. In addition, examples of the forecasts and verification results will be shared, along with some comments from users and the public on the hourly temperature forecasts during the eclipse. Finally, we will share experiences from the nearly half dozen WFOs in the Southeast and mid-Atlantic that used the tools and provide some recommendations for handling these events in the future, including the 2024 total solar eclipse.