Forecasting California Precipitation Using a Cointegrated Relationship with the North Pacific High Sea Level Pressure Anomaly

A cointegrated relationship has been identified between the sea level pressure anomaly at the climatological location of the North Pacific High (NPH) and seasonal precipitation over California (Costa-Cabral et al., J. Clim., 2016). Here we demonstrate how this cointegration can be used for seasonal precipitation forecasting at different California locations including all main runoff-producing basins. We apply the new methodology to a) northern Sierra Nevada stations of the “eight station index” (8SI), b) the central Sierra Nevada stations of the “five-station index” (5SI), c) the southern Sierra Nevada stations “six station index” (6SI), d) at a San Francisco Bay station. We demonstrate that season-to-season precipitation forecasts based on the cointegrated relationship with the NPH have higher measures of skill than those based on regression methods incorporating the NPH anomaly. The new methodology is a powerful approach for forecasting California winter precipitation.