Interdecadal variation of tropical cyclone genesis longitudes over the western North Pacific

Statistical change-point analysis was used to examine a significant change in the average longitude locations of tropical cyclone (TC) genesis from June to October between 1979 and 2020. It was observed that since 1998, the TC genesis location has shifted westward. This study investigates the causes of this interdecadal shift in the western North Pacific (WNP). During the recent period (1998–2020), a westward shift was noted in precipitation, outgoing longwave radiation, precipitable water, and total cloud cover. The primary driver for this shift is the negative phase of the Pacific Decadal Oscillation during the second period. A positive sea surface temperature (SST) anomaly enhances convection over the South China Sea and adjacent waters west of 140° E, which retreats the monsoon trough toward the west. Furthermore, the Rossby wave response to a negative SST anomaly over the central and eastern Pacific causes the WNP subtropical high in the lower troposphere to move further west, pushing the monsoon trough in the same direction. The westward shifts in convection and circulation are maintained by a strengthened Walker circulation.