Seasonal Dependent Relationship of Tropical Cyclone Decadal Variation Between Western North Pacific and North Atlantic

Abstract Tropical cyclone (TC) activity over the western North Pacific (WNP) and North Atlantic (NA) shows pronounced decadal variability linked to the AMO and PDO. We reveal a strong seasonal dependence in their inter‐basin relationship. A robust antiphase appears in autumn (SON), but no significant relationship exists in summer (JJA). The AMO–PDO teleconnection remains active in both seasons, ruling out sea surface temperature (SST) forcing as the cause. Instead, the weak summer linkage arises from substantially reduced decadal coherence of NA TC genesis in JJA, whereas WNP TC variability remains seasonally consistent. The reduced NA TC coherence in JJA coincides with anomalously strong vertical wind shear (VWS), which results from alignment of anomalous winds with the climatological background and suppressed convection due to cooler SST. Hence, the intensified summer shear acts as an environmental filter decoupling the inter‐basin relationship, while weaker autumn shear permits a robust WNP–NA linkage.