Classification of cold and warm episode seasons based on the pattern and magnitude of SST anomalies in the tropical Pacific. Seasons are December-February(DJF), January-March(JFM), February-April(FMA), March-May(MAM), April-June(AMJ), May-July(MJJ), June-August(JJA), July-September(JAS),August-October(ASO), September-November(SON), October-December(OND) and November-January(NDJ). W-, W, W+, C-, C, C+, N represent weak, moderate, strong warm/cold and neutral conditions,respectively. Year DJF JFM FMA MAM AMJ MJJ JJA JAS ASO SON OND NDJ 1950 C C+ C+ C C C C C C C C C 1951 C C C- C- N N W- W- W- W- W- W- 1952 N N N N N N N N N N N N 1953 W- W- W- W- W- W- W- W- W- N N N 1954 N N N N N C- C- C C C C C 1955 C C C C C C C C C C+ C+ C+ 1956 C C C C- C- C- C C C C- C- C- 1957 N N N W- W- W- W W W W W W 1958 W+ W+ W+ W W W W- W- W- W- W- W- 1959 W- W- W- N N N N N N N N N 1960 N N N N N N N N N N N N 1961 N N N N N N N N N N N N 1962 N N N N N N N N N N N N 1963 N N N N N N W- W- W- W W W- 1964 W- N N C- C- C- C- C- C- C C C 1965 C- C- N N W- W- W W W W W W 1966 W W W W- W- W- W- W- W- N N N 1967 N N N N N N N N N N N N 1968 N N N N N N N N W- W W W 1969 W W W W W W W- W- W- W W W 1970 W- W- W- N N N C- C- C- C C C 1971 C C C C- C- C- C- C- C- C- C- C- 1972 N N N W- W W W+ W+ W+ W+ W+ W+ 1973 W W W- W- N C- C- C C C+ C+ C+ 1974 C+ C+ C+ C C C C- C- C- C- C- C- 1975 C- C- C- C- C- C- C C C C+ C+ C+ 1976 C C C- C- N N W- W- W- W- W- W- 1977 W- W- W- N N N N N N W- W- W- 1978 W- W- W- N N N N N N N N N 1979 N N N N N N N N N W- W- W- 1980 W- W- W- W- W- W- N N N N N N 1981 N N N N N N N N N N N N 1982 N N N W- W- W- W W W W+ W+ W+ 1983 W+ W+ W+ W+ W+ W+ W W- N N C- C- 1984 C- C- C- C- C- C- N N N C- C- C- 1985 C- C- C- C- C- C- N N N N N N 1986 N N N N N N W- W- W- W W W 1987 W W W W W W W W W W W W 1988 W- W- N N C- C- C- C- C- C C+ C+ 1989 C+ C+ C+ C C C- C- N N N N N 1990 N N N W- W- W- W- W- W- W- W- W- 1991 W- W- W- W- W- W- W W W W W W 1992 W+ W+ W+ W+ W+ W W W- W- W- W- W- 1993 W- W- W- W W W W- W- W- W- W- W- 1994 N N N N N N W- W- W- W W W 1995 W- W- W- N N N N N N C- C- C- 1996 C- C- C- N N N N N N N N N 1997 N N W- W- W W W+ W+ W+ W+ W+ W+ 1998 W+ W+ W+ W W W- N C- C- C C C 1999 C C+ C+ C+ C C C- C- C- C C C+ 2000 C+ C+ C+ C C C- C- N N C- C- C Prior to 1950 it is difficult to determine the season-by-season characteristics of the tropical Pacific. For years prior to 1950 we use data found in scientific papers. The strength (+, , ) of the epsiodes is inferred from the SOI (whenever possible) Warm (ENSO) Episodes (sources: Rasmusson and Carpenter 1983, Monthly Weather Review; Ropelewski and Halpert 1987, Monthly Weather Review) 1877/78+, 1880?, 1888-89, 1896/97+, 1899 , 1902/03 , 1905/06+, 1911/12+, 1913/14, 1918/19+, 1923, 1925/26+, 1932, 1939/41 (1939/40, 1940/41+), 1946/47 Cold Episodes (sources Roplewski and Halpert 1989, Journal of Climate; Climate Daignostics Bulletin) 1886, 1889/90+, 1892?, 1903/4+, 1906-1908+, 1909/10+, 1916/18+, 1924/25, 1928/29, 1938/39+ Some years are listed as both cold and warm episode years (e.g., 1925, 1939). In those cases there was a rapid transition between the two extreme states during the course of the year.