Evaluation of Skillful All-Season S2S Prediction of U.S. Precipitation using the MJO and QBO

Although useful at short and medium-ranges, current dynamical models provide little additional skill for precipitation forecasts beyond Week 2 (14 days). Here, we apply an empirical model that uses the Madden-Julian oscillation (MJO) and quasi-biennial oscillation (QBO) as predictors to forecast anomalous (i.e., categorical above- or below-normal) weekly precipitation at Weeks 3 through 6 (15-42 days) across the contiguous U.S. and Alaska during all seasons. In almost all regions and seasons, the model provides “skillful forecasts of opportunity" for 20-50% of all forecasts valid Weeks 3 through 6. We also show that the addition of the QBO as a predictor increases the frequency of skillful forecasts of opportunity in over 90% of the contiguous U.S. and Alaska during winter, spring, and summer (75% during fall).