Skillful Prediction of the Summer North Atlantic Oscillation: Opportunities From Circumglobal Waveguide Dynamics

Abstract The Summer North Atlantic Oscillation (SNAO) is the dominant climate pattern that affects heatwaves and droughts across Europe and downstream over Asia. However, its seasonal prediction remains challenging. While recent studies have identified stratospheric pathways for improving SNAO prediction, the role of tropospheric wave dynamics remains unclear. Using a latest‐generation large‐ensemble seasonal forecasting system, we find that the model exhibits limited SNAO prediction skill and underestimates downstream climate impacts. These limitations are associated with deficiencies in circumglobal waveguide dynamics. Subsampling ensemble members that best capture circulation anomalies near circumglobal teleconnection centers or tropical/monsoon rainfall that forces the teleconnection is accompanied by significantly improved SNAO prediction. Furthermore, deficiencies in the model circumglobal waveguide, particularly over the Mediterranean and North Atlantic with underestimated background zonal winds and erroneous curvature, may disrupt wave propagation. Refining these dynamical features could improve teleconnection representation and SNAO prediction, aiding summer climate risk mitigation.