Indian Ocean Convection Modulates the Early‐Winter Pacific‐North American Response to El Niño

Abstract The El Niño‐Southern Oscillation is a dominant driver of Pacific‐North American (PNA) variability on seasonal‐to‐interannual timescales through its influence on tropical Pacific convection. However, the early‐winter PNA response exhibits pronounced event‐to‐event diversity during El Niño. Here we show that this diversity is closely linked to variations in tropical convection across the Indo‐Pacific. Strong El Niño‐related convection over the tropical Pacific enhances convection over the tropical Indian Ocean via the Walker circulation. This Indian Ocean convection suppresses the early‐winter establishment of the PNA, thereby weakening the extratropical atmospheric response to Pacific forcing. Idealized linear baroclinic model experiments consistently reproduce these opposing influences, supporting a dynamical pathway through which Indo‐Pacific convection modulates early‐winter PNA variability during El Niño.