Interannual Changes of Tropical Cyclone Prevailing Tracks in the Western North Pacific

Abstract: While the interannual variations of tropical cyclone (TC) formation location and large-scale steering flow are closely associated with TC tracks, in this study the ENSO influence on the peak-season (July-September) TC prevailing tracks in the western North Pacific (WNP) basin is investigated based on the selected 14 El Niño years and 14 La Niña years during the period 1950-2007 with a statistical model for simulating TC formation and a trajectory model for simulating TC tracks. It is found that the trajectory model can simulate the primary features of TC prevailing tracks on the interannual time scale. In the El Niño years, the significant enhancement of TC activity primarily occurs south of 20ºN, especially east of 130ºE, which is a combined result of changes in both large-scale steering flow and TC formation location. TCs taking the northwestward prevailing track, by which TCs affect East Asia, including Taiwan Island, China mainland, Korea and Japan, tend to move more westward in the El Niño years while taking a more northward track in the La Niña years. Numerical simulations suggest that the change in the prevailing track primarily results from the ENSO-related changes in large-scale steering flows. The study suggests that the ENSO-related changes in large-scale steering flow and TC formation location can have a remarkable influence on TC prevailing tracks.