Statistical linkage between coastal El Nino-Southern Oscillation and tropical cyclone formation over the western North Pacific

This study investigates the modulation of tropical cyclone (TC) formation over the western North Pacific (WNP) by coastal El Nino-Southern Oscillation (ENSO). There is a significant inverse relationship between WNP TC frequency during July-October from 1961 to 2019 and simultaneous Nino 1+2 sea surface temperature anomalies. TC formation is significantly suppressed and enhanced over the subtropical and equatorial WNP during coastal El Nino, respectively, while TC formation exhibits opposite-signed anomalies during La Nina. This north-south dipolar pattern during coastal ENSO is distinct from the pattern observed in basin-wide ENSO events. Additional analyses show that coastal ENSO influences WNP TC formation through modulation of the large-scale environment. Changes in mid-level moisture and low-level vorticity appear to be the primary large-scale influences on TC formation during both coastal ENSO phases. These changes can be further linked to the anomalous large-scale circulation over the WNP during coastal ENSO.