Abstract Kuroshio‐Oyashio extension sea surface temperature (SST KOE ) anomalies modulate local marine ecosystems and nearby climate extremes. Recent studies have preliminarily revealed that the SST KOE anomalies reverse in early and late autumn, but its precursor drivers are still unclear. This study demonstrates that the transition of the Eastern Pacific El Niño–Southern Oscillation (EP‐ENSO) from March to July plays a pivotal role in driving the SST KOE reversal. As EP‐ENSO transitions, autumn convective activity over the Maritime Continent strengthens due to an enhanced Walker circulation. In early autumn, localized convection near the Java Sea excites the Rossby wave train propagating from the Mariana Islands to the northern Hawaiian Islands and reaching the Gulf of Alaska. In late autumn, widespread convection across the Maritime Continent triggers the West Pacific‐like teleconnection pattern. These distinct atmospheric Rossby wave trains—and the resulting opposite‐phase local atmospheric circulation over the mid‐latitude Northwest Pacific—are supported by tropical Pacific pacemaker simulations and linear baroclinic model experiments. Changes in shortwave radiation and turbulent heat flux, driven by shifts in local atmospheric circulation, are the dominant drivers of the SST KOE reversal. This research provides new insights into tropical–mid‐latitude interactions, emphasizing that seasonally averaged diagnostics may obscure key thermodynamic and dynamic processes at sub‐seasonal timescales, potentially introducing biases in climate prediction.
Ma et al. (Mon,) studied this question.