Influence of Low‐Frequency PNA Variability on MJO Teleconnections to North American Atmospheric River Activity

The Madden-Julian oscillation (MJO) modulates atmospheric river (AR) activity along the West Coast of North America. forecast skill ARs based solely on MJO phase is limited, motivating identification other predictive factors. Here we show that low-frequency variability Pacific/North American (PNA) pattern mostly independent MJO, and monthly PNA influences MJO-AR relationship much more robustly than large-scale patterns such as El Niño Southern Oscillation quasi-biennial oscillation. During PNA+ conditions, when Pacific jet exit region located further east average, baroclinic wave packets extend downstream toward clear contrast in packets' zonal scale results partitioning active inactive AR phases. influence most significant over Northwest America, where landfall frequent, with implied forecasting beyond 20 days.