Emerging dynamical storylines can constrain near-term projections of the Southern Hemisphere Eddy Driven Jet

The Eddy Driven Jet (EDJ) in the Southern Hemisphere guides synoptic systems, thereby shaping regional weather. Uncertainties in climate models in projecting large-scale drivers of the EDJ including tropical warming, stratospheric polar vortex, strengthening, and asymmetric tropical Pacific warming—hinder informative predictions of EDJ trends and associated regional outcomes such as extreme precipitation. Here we develop a causal framework that combines observations, reanalysis datasets, and dynamical storylines estimated from the Coupled Model Intercomparison Project (CMIP) projections to attribute past EDJ changes in summer and predict plausible future trajectories. Our findings indicate that tropical warming has evolved along the low end of plausible trajectories, while the stratospheric polar vortex shows robust strengthening, strongly influencing observed EDJ trends. Our results suggest that 50% of the observed EDJ latitude shift is attributable to global mean warming, and the remaining 50% to remote drivers. Importantly, climate models appear to underestimate EDJ strengthening during austral summer, while the proposed dynamical storylines are able to capture the observed trend. By integrating causal inference with climate storylines, our approach narrows the divide between attribution and prediction, offering a physically grounded method to estimate plausible pathways of future climate change.