Report Makes Case for Funding Longer-Range Weather Forecasting by ACWA Staff Feb 10, 2021 Water News Sub-seasonal to seasonal forecasts could someday give western water managers as much as a two-year head start in planning for either a wet or dry winter. The scientific methodology already exists for what is known as S2S precipitation forecasting, but putting it to work requires improving weather and climate models and buying enough super-computer time to run the models to test them. Now, a National Oceanic and Atmospheric Administration (NOAA) report could spur Congress to approve the $15 million annual investment necessary to translate S2S forecasting from concept to implementation through pilot projects in the West. An advocacy effort is underway to fund the NOAA report to Congress and includes the Atmospheric River Coalition, of which ACWA is a member, as well as ACWA member agencies Sonoma Water, Yuba Water Agency and Orange County Water District. The Western States Water Council is also supporting the call for funding. The idea is to make S2S as much a priority as improvements in hurricane forecasting on the East Coast. The Western States Water Council and supporting agencies will work together on a support letter that will be distributed during February, when Congress will start considering funding requests, said Brad Sherwood, ACWA Region 1 Chair and Sonoma Water’s Division Manager for Community and Government Affairs. “It’s a water management tool that will benefit every ACWA member,” Sherwood said, explaining that it will dovetail with the ability to apply Forecast Informed Reservoir Operations, or FIRO, which allows for flexibility in reservoir storage in coordination with weather forecasts. “FIRO is micro water management where as S2S is macro water management,” Sherwood said. Conventional weather forecasts are issued with lead times of out to about two weeks. Their skill degrades rapidly after the first week. S2S forecasts extend beyond the domain of a weather forecast, with lead times of up to six weeks (sub-seasonal) to a year or two (seasonal). Seasonal forecasts do not extend to predicting individual weather events, such as atmospheric rivers, but answer a question frequently asked by water managers – will this winter be wet or dry? When the National Weather Service conducted a drought service assessment in 2014, the more than 100 managers surveyed overwhelmingly identified an accurate seasonal precipitation forecast as the high-priority service that should be provided, according to Jeanine Jones, Interstate Resources Manager for the California Department of Water Resources. Jones, a longtime supporter of improving S2S forecasting, led the formation of a Western States Water Council S2S coalition that advocated for the Weather Research and Forecasting Innovation Act, passed by Congress in 2017. The act required NOAA to draft the report that encapsulates the value of S2S forecasting and why it should be funded. “It’s a pretty big milestone for this effort,” Jones said. “It took a lot of work to get there.”
