ENSO Consensus Explained

1997ElNino

There are many ways El Nino/La Nina metrics as they range from Oceanic Nino Index (ONI), Multivariate ENSO Index (MEI), Southern Oscillation Index (SOI), and Japanese Meterological Agency ENSO Data.

I created my own El Nino/La Nina index. It is based ERSST v4 Anomaly of Region 1+2, 3, 3.4, and 4, Japanese Meterological Agency ENSO Data, SOI, and MEI. I use a weighted average system. Here is the formula I used.

(ERSST v4 Region 1+2 Anomaly*15)+(ERSST v4 Region 3 Anomaly*5)+(ERSST v4 Region 3.4 Anomaly*25)+(ERSST v4 Region 4 Anomaly*5)+(JMA ENSO*20)+(-(SOI)*20)+(MEI*25))/(15+5+25+5+20+20+25)

Here is a monthly table of ENSO Consensus. It starts at 1870. For El Nino and La Nina to be considered, it has to be consecutive for at least seven months.

ENSO Consensus
Strong La Nina = 12.25

ENSO Consensus
Strong La Nina = 12.25

Wonder what years had strong El Nino and La Nina? It is based on highest for El Nino or lowest for La Nina.

Strong El Nino (Based On Monthly Average >= 12.25)
1877-1878
1888-1889
1896-1897
1899-1900
1902-1903
1904-1905
1930-1931
1940-1941
1957-1958
1965-1966
1972-1973
1982-1983
1986-1987
1991-1992
1992-1993 (Burst of El Nino in spring 1993)
1997-1998
2014-2016

Strong La Nina (Based On Monthly Average = 12.25)
1957-1958
1965-1966
1972-1973
1982-1983
1986-1987
1991-1992
1992-1993
1997-1998

Strong La Nina Since 1950 (Based On Monthly Average <= -12.25)
1949-1950
1954-1957
1964-1965
1970-1971
1973-1976
1988-2001
2007-2008
2010-2011

There have been more strong La Nina than El Nino since 1950. Again this reflects that since 1950 we have mostly been in a cool PDO phase, which has account 36 years, while warm PDO have accounted 27 years.

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