California receives about half of its annual water supply from a handful of winter storms called atmospheric rivers. Predicting the arrival and intensity of those storms would greatly benefit water managers, reservoir operators, and flood prevention agencies in their work to sustainably manage water supply and protect people and property from flood damage. The trouble is, weather forecasting beyond a week becomes unreliable. At 7 days out, forecasts are about 70 percent accurate, but the 14-day forecast is only 7 percent accurate. “That just isn’t adequate for water management,” said DWR Director Grant Davis.
On Nov. 9, Mr. Davis and DWR Interstate Resources Manager Jeanine Jones joined experts from state, federal, and local governments for a workshop, co-sponsored by DWR and the Association of California Water Agencies, on improving “season-to-season” weather forecasting accuracy. Achieving the goal of accurate long-range precipitation predictions will require continued investments in forecasting technology and infrastructure. New radar stations are being installed at Lake Oroville and near Carquinez Strait to gather information on incoming atmospheric rivers.