After 5 years of drought, record rains occurred in many areas of California, including Nevada County last winter. The Department of Water Resources says the dramatic swing in conditions highlights the need to develop better long-range forecasting, to cope with the state’s highly variable annual precipitation. Interstate Resources Manager, Janine Johnson, says they’re developing innovative technology to forecast land-falling atmospheric rivers. These are warm systems with heavy amounts of rain that greatly benefit the water supply but can also cause flooding. Johnson says such systems weren’t even known to exist until the 1990’s, thanks to newly-designed radar…

click to listen to Janine Johnson

The DWR director says current short-term forecasting for 7 days out is 70% accurate, while the 14-day forecast is only 7% accurate. And Johnson says seasonal precipitation outlooks are still largely speculative…

click to listen to Janine Johnson

The DWR says more accurate forecasting would help to better manage reservoir levels, to deal with significant inflows, such as what occurred at Oroville Dam in February. Johnson says last winter the west coast had more than 50 atmospheric rivers, but you only actually need 5 to 6 large storms to produce an adequate water supply.