In his latest newsletter on climate and agricultural conditions, Johan van den Berg of Santam Agriculture says favourable rainfall conditions for most of the winter rainfall area, are likely to remain steadfast until September. There are also strong indications that sea surface temperatures will become more neutral.
Current climate conditions
Relative mild conditions over most of the summer rainfall area is still present for this time of the year, with below average temperatures. Very little or no rain occurred but that is normal for this time of the year. More irrigated and dryland wheat is planted in the central parts of the country due to very good water availability from surface water resources. Above average rainfall in late summer and autumn allows for dry land production in the rooting zone.
The harvesting process of the maize crop in the western Free State and North West province is delayed compared to previous years. It is expected that the harvesting of maize will only be completed towards the second part of August which is about two to four weeks later than normal. Most of the sunflower, sorghum and soya beans are harvested.
Grazing conditions in the western parts of the North West province, most of the Northern Cape, parts of the Eastern Cape and smaller parts of the Western Cape and Limpopo, still suffer disaster drought conditions. In some of these areas the drought conditions have been present since 2012.
Conditions improved for large parts of the winter rainfall region with regular rainfall since May 2019. West Coast areas close to the Namibian border received some rain although the interior to the east still remains dry. Conditions for winter crops in the Swartland and Southern Cape area are very favourable.
El Niño and the Indian Ocean
Sea surface temperatures in all Niño regions are now reaching the neutral phase of ENSO (away from El Niño), more regularly. Three of the four Niño regions were within the +0,5˚C and -0,5˚C range on 15 July 2019. Cooler water from deeper oceanic layers are now replacing warmer surface waters. Although there is a lack of consensus regarding global forecasts about the El Niño status, it is quite significant that changes in temperatures are now starting to occur. It seems as if the forecast for neutral conditions now exceed the probability of El Niño for the summer season of 2019/20.
The Southern Oscillation Index that measures coupling between surface and weather systems, is still in an El Niño-like pattern. There is usually a lag time so it is expected that El Niño weather patterns will prevail for the next few months.
Warming of the Western Indian Ocean resulted in the development of a positive Indian Ocean Dipole Index (IOD). This is not good news for the summer rainfall area, especially for spring and early summer rainfall. However, forecasts are showing a weakening towards November.
Low winter rainfall
The winter period is traditionally very dry and current outlooks also indicate a low probability for winter rainfall, especially in the central to northern parts. With the development of a positive IOD, it can have a negative effect on the probabilities for rain in spring and early summer. The outlook that favours a more neutral state of ENSO (away from current weak El Niño levels) can favour mid-to-late summer rainfall but also reduces the likelihood for spring and early summer rain. It is possible that spring rain may occur over the southern parts of the summer rainfall area as a result of the El Niño lag effects.
A number of areas in South Africa are winter rainfall areas and cold fronts now regularly produce rainfall over the western and south-western parts of the Western Cape and even areas of the Northern Cape. This is likely to continue for the next few weeks until September. Lots of rainfall is expected in the last week of July and beginning of August.
It is likely that very little rain will occur in Namibia over the next few months. There is also the possibility of a late start regarding the summer rainfall season of 2019/20.
Summary and conclusions
Although we are still very early in the current season, there are positive indications that the current El Niño status will change to more neutral conditions in late winter and early spring. This can have positive effects on mid-to-late summer rainfall.
The winter rainfall region also seems to have a good season across most areas with more rain expected. This can lead to very good winter crop yields in especially the Swartland and surrounding areas. – Santam Agriculture