Senwes Scenario December 2018 / January 2019 | Page 35

GRAIN BROKERS
Table 1: El Niño and La Niña classification by years.
La Niña
El Niño
Weak
(0.5 to 1°C) Moderate
(1 to 1.5°C) Strong
Very Strong
Weak
Moderate
(1.5 to 2°C)
(>2°C)
(-0.5 to -1°C) (-1 to -1.5°C) 1952-1953 1951-1952 1957-1958 1982-1983 1954-1955 1955-1956 1973-1974
1958-1959 1968-1969 1972-1973 2015-2016 1971-1972 1995-1996 1988-1989
1953-1954
1969-1970
1976-1977
1977-1978
1979-1980
2004-2005
1963-1964
1986-1987
1994-1995
2002-2003
1965-1966
1987-1988
1997-1998
1991-1992
2009-2010
2014-2015
1964-1965
1974-1975
1983-1984
1970-1971
2011-2012
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
Figure 1: SOI-values
Figure 2: Oceanic Niño Index(ONI).
Celsius intervals, as indicated in Figure
4. This classification makes it possible to
classify previous seasons according to
the type of season experienced, as sum-
marised in Table 1.
Source: The Long paddock
Source: GG Weather
Against this background it becomes
possible to create a new expectation for
the new season on the basis of various
models projecting the development of
sea surface temperatures. The aver-
age expected sea surface temperature
projected at present, indicates that it
is estimated that the temperature can
be approximate 0.8 degrees Celsiums
warmer than normal from November to
February. Per definition this expectation
indicates a weak El Niño event and the
probability of such an event is estimated
at 70%.
However, there is an outsider to be
taken into account in any consideration
which relates to season climate expec-
tations and rainfall. This aspect is the
origination and development of tropical
cyclones which are known for withdraw-
ing moisture from central South Africa
and which have a negative impact on
the probability of rain. The causes and
measurement of these phenomena are
indicated by the East Indian Dipole (EID).
When the EID-value is positive, it will
indicate warmer than normal sea surface
temperatures against the east coast of
Africa. This scenario causes increased
evaporation which drives moisture over
the country. This moisture results in rain
over the Indian Ocean.
The EID-value is positive at present,
but the projections of the EID-values
during January and March 2019 seem to
be neutral, which indicates that tropical
cyclones will probably not pose a threat
for rainfall during the critical pollination
period.
In summary - the objective of this arti-
cle is not to make a rainfall prediction for
the 2018-19 season. The information con-
tained herein is based on actual historic
realisations of weather phenomena and
models tested over time. The conclusion
to be made from the expectations is that
the 2018-19 production season will prob-
ably be characterised as a weak El Niño
season.
However, it is important to evaluate this
expectation in context by looking at the
impact of an El Niño event on yield over
time. This yield expectation can further be
linked to rainfall realisation during similar
production seasons in the Senwes area.
We will specifically look at the impact of a
weak El Niño event in the next article.
SENWES SCENARIO | TECHNOLOGY & INNOVATION 2018
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