Advancing atmospheric river forecasts into subseasonal‐to‐seasonal time scales

Abstract

Abstract Atmospheric rivers are elongated plumes of intense moisture transport that are capable of producing extreme and impactful weather. Along the West Coast of North America, they occasionally cause considerable mayhem—delivering flooding rains during periods of heightened activity and desiccating droughts during periods of reduced activity. The intrinsic chaos of the atmosphere makes the prediction of atmospheric rivers at subseasonal‐to‐seasonal time scales (3 to 5 weeks) an inherently difficult task. We demonstrate here that the potential exists to advance forecast lead times of atmospheric rivers into subseasonal‐to‐seasonal time scales through knowledge of two of the atmosphere's most prominent oscillations, the Madden‐Julian oscillation (MJO) and the quasi‐biennial oscillation (QBO). Strong MJO and QBO activity modulates the frequency at which atmospheric rivers strike—offering an opportunity to improve subseasonal‐to‐seasonal forecast models and thereby skillfully predict atmospheric river activity up to 5 weeks in advance.