GRAIN BROKERS
Weak El Niño years
What happened in the past?
The previous edition contained an article on the background, origin and development of
ENSO (El Niño Southern Oscillation) events. This article is a follow-up in which we look
at a specific classification of ENSO in the form of a weak El Niño event, which is present
for the 2018/2019 production season.
By Frans Dreyer
Manager: Senwes Grain Brokers
A
weak El Niño event is identified
when sea surface temperatures
are warmer than normal, but fall
within a specific grade Celsius
band. Sea surface temperatures are
expressed as a norm by means of monthly
Oceanic Nino Index (ONI) values. Every
monthly ONI value is the three-month aver-
age of the sea surface temperature in the
Nino 3.4 area. This classification was sub-
divided over time to indicate the expected
intensity of an El Niño or La Niña phe-
nomenon. The subdivision is made in 0.5°
Celsius intervals as indicated in Figure 1.
This classification makes it possible to
categorise previous seasons according to
the type of season experienced, as sum-
marised in Table 1.
An evaluation of past El Niño and La
Niña events over the long term confirms
the actual impact thereof on yield expec-
tations becomes evident.There is no clear
evidence that La Niña years will be charac-
terised by higher yields and El Niño years
34
Figure 1: Oceanic El Niño Indeks (ONI).
Source: GG Weather
Table 1: El Niño and La Niña year classification.
La Niña
El Niño
Weak
(0.5 to 1°C) Moderate
(1 to 1.5°C)
1952-1953 1951-1952
1958-1959 1968-1969
1976-1977 1994-1995
1953-1954
1969-1970
1977-1978
1979-1980
2004-2005
2014-2015
SENWES SCENARIO | MIND-SHIFT 2019
1963-1964
1986-1987
2002-2003
2009-2010
Strong
Very Strong
Weak
Moderate
(1.5 to 2°C)
(>2°C)
(-0.5 to -1°C) (-1 to -1.5°C)
1957-1958
1965-1966
1972-1973
1987-1988
1991-1992
1982-1983 1954-1955
2015-2016 1971-1972
1997-1998
1955-1956 1973-1974
1995-1996 1988-1989
1964-1965 1970-1971
1974-1975 2011-2012
1983-1984
1984-1985
2008-2009
2016-2017
1975-1976
1998-1999
1999-2000
2007-2008
2000-2001
2005-2006
Strong
(<-1.5°C)
2010-2011
`
2017-2018
Source: GG Weather