The tropical cyclone distribution in the western North Pacific during the El Nino-La Nina swing of 1997–99: Extraordinary interannual changes

During 1997-99, the global climate underwent a dramatic swing from major El Nino (1997) to persistent La Nina conditions (1998-99). Accompanying this large interannual global climate change were extraordinary changes in the distribution of tropical cyclones in the western North Pacific. A dramatic change occurred to the genesis locations of the tropical cyclones: many formed far to the east of normal during 1997; and most formed far to the west of normal during 1998 and 1999. The annual number of tropical cyclones in the western North Pacific was near normal during 1997 and at record low levels during both 1998 and 1999. Also, there were 11 typhoons of extreme intensity in excess of 125 kt (i.e., super typhoons) during 1997 and only two such typhoons during 1998 and one during 1999.