Divergent Influences of Oceanic Western Boundary Currents on Weak and Strong Tropical Cyclones

Abstract Tropical cyclones (TCs) in the Northern Hemisphere often cross oceanic western boundary currents (WBCs), yet how these warm currents modulate TC intensity remains unclear. We analyze TCs traversing the Kuroshio and Gulf Stream during 1993–2025 and find that weak TCs respond more favorably than strong TCs. Weak TCs crossing WBCs before their lifetime maximum intensity (LMI) strengthen by 30.9% and intensify faster than in the preceding stage, whereas those crossing after LMI weaken by only 13.2%, exhibiting slower decay. In contrast, strong TCs generally weaken over WBCs. These contrasting responses arise from differences in latent heat flux modulated by TC‐induced SST cooling. Over the past three decades, WBC modulation has strengthened for weak TCs but weakened for strong TCs. These trends are linked to WBC upper‐ocean warming and rising strong‐TC intensity at WBC entry, respectively. Our findings highlight the growing role of WBC thermal conditions for coastal TC intensity prediction.