Spring Westerly Winds Shape Early Precursors of El Niño Diversity Across the Spring Predictability Barrier

Abstract Predicting El Niño diversity, specifically the distinction between Eastern Pacific (EP) and Central Pacific (CP) events, remains challenging due to the boreal spring predictability barrier (SPB) and the inconsistent detection inherent in discrete wind‐burst metrics. Here, we present a five‐phase precursor scheme that tracks the monthly evolution of equatorial westerly wind anomalies over 12 months, using wind intensity and spatial centroid metrics from the 1980–2024 reanalysis data. EP and CP precursors diverge as early as boreal spring, when EP‐type wind intensity significantly surpasses CP‐type intensity, whereas CP‐type winds shift anomalously eastward. Spatial composites further reveal an intensity‐position trade‐off governing Kelvin wave excitation, in which stronger wind intensity in EP events compensates for their less favorable, more westward locations. Conversely, meridional centroid tracking fails to discriminate event types until boreal winter. These findings provide a physically interpretable precursor signal for anticipating El Niño within the SPB.