Limited Influence of Pre‐Existing Tropical Cyclones on Subsequent Cyclogenesis in the Western North Pacific

Abstract Previous studies suggest that a tropical cyclone (TC) may contribute to the genesis of another TC to its east or southeast in the western North Pacific (WNP) through Rossby wave dispersion. However, the influence of a pre‐existing TC (PTC) has not been fully clarified in realistic simulations. This study conducted 42 numerical experiments (NPTC) for 1981–2022, in which a PTC was removed by horizontal smoothing from the initial conditions 120 hr before the genesis of a subsequent TC (STC). Compared to control simulations with the PTC (WPTC), the number of STC formations was slightly larger (WPTC: 31, NPTC: 33). The intensities of common STCs are very similar. STCs were typically located to the south or southwest of a subtropical high. The experiments showed wave‐like anomaly patterns in the vorticity field southeast of PTCs and in the geopotential height field northeast of the PTCs. Vertical wind shear (VWS), enhanced by PTC outflows, created an unfavorable environment for STC formation and intensification. Reanalysis data supported strong VWS and a similar wave‐like pattern. A positive sea surface temperature anomaly over the central equatorial Pacific induced westerly wind anomalies in the southeastern WNP. The spatial collocation of PTCs and STCs was frequently observed when the active eastern convection is expected by the indices of Madden–Julian Oscillation, Boreal Summer Intraseasonal Oscillation, and El Niño–Southern Oscillation. These conditions promote TC genesis farther east, suggesting that such collocation does not imply PTC‐induced formation. Thus, impact of PTCs appears less significant than previously assumed.