The interannual variability of intense western Pacific typhoons during the 1997–1999 El Nino/La Nina cycle

During the 1997 typhoon season, eleven supertyphoons (1-minute mean maximum sustained surface winds of 130 knots or greater) were observed in the northwestern Pacific basin. This represents a large variability from the climatological (1960-1998) annual average of 4.3. There was also a large interannual difference between 1997 (El Nino year after March) when the eleven supertyphoons occurred and 1998 (La Nina year after June) when only three were observed. As the La Nina continued through 1999, only one supertyphoon occurred during the entire year.

Sea-surface temperature data are analyzed for the years 1997, 1998, and 1999 and compared to each other and with climatology to detect patterns and anomalies associated with the large variation in the number of supertyphoons. Results will be presented at the conference