In his latest newsletter on climate and agricultural conditions, Johan van den Berg of Santam Agriculture says very dry conditions are currently dominating most of the country. El Niño Southern Oscillation is in a neutral state with the Indian Ocean having the biggest influence in this regard.
Some rainfall is possible in the second week of November over the central to eastern summer rainfall area. Rainfall conditions are likely to improve after November through April during the latter part of the summer season.
Current climate conditions
Unfavourable climate conditions are currently prevalent throughout the country. Heat wave conditions persist over large parts of the summer rainfall area. Drought conditions are increasing from the west towards the central, northern and eastern parts.
Feed for animals is becoming increasingly scarce and the drought disaster areas are expanding daily. Dryland wheat production in the Western Cape and the Free State suffered damage due to the dry and extremely hot conditions. Damage may also occur on irrigated winter crops due to high evaporative demand and hot conditions.
Another serious consequence caused by the hot and dry conditions is that the planting time for summer crops is running out. The eastern summer crop production area is most affected.
In the cooler parts of the Eastern Free State and Mpumalanga, summer crops should emerge towards the second part of November. This leaves less than a month to cultivate and plant. In many areas it is still too dry to do primary cultivations. Dam levels are also decreasing rapidly.
El Niño and the Indian Ocean
After a mini El Niño spell where the Niño regions have warmed slightly since middle September 2019, some cooling has taken place during October. Three of the four Niño regions were less than 0,5˚C warmer than normal, indicating that it is in the ‘neutral range’.
However, the Southern Oscillation Index (SOI), which measures surface and weather system interaction, is still El Niño-like. It is indicated that a neutral ENSO phase will remain for the rest of the season. However, it will lean towards the El Niño side of neutral due to subsurface warming.
The Indian Ocean is currently in a very strong positive phase of the Indian Ocean Dipole (IOD) Index. There is cooler water towards the North-western parts of Australia and warmer water towards the Central and Southern African coastline.
This is very negative in terms of rainfall over the Southern African subcontinent due to the moisture ‘outflow’ from Central Africa towards the Indian Ocean and not towards the south.
It is also mainly responsible for the high pressure system currently dominating Southern Africa. Forecasts indicate that the IOD will return to neutral conditions from December 2019.
Expected rainfall and temperature conditions
The current very strong positive IOD will negatively affect the summer rainfall area during the next two weeks. Short-term forecasts are showing some improvement for rainfall in the second week of November over the central to eastern parts of the country. There will also be some lower temperatures, but unfavourable conditions will continue throughout the rest of October.
Conditions for rainfall might improve after November when the Indian Ocean conditions will become less prominent and the effect of neutral ENSO conditions can come into play.
Winter rainfall areas
Some rainfall associated with a cold front is possible in the last week of October with lower daytime temperatures.
Prospects for rain are not favourable over the next weeks. However, some rain may occur in the second week of November over the north-eastern parts. Conditions are likely to improve in the second part of the season.
Summary and conclusions
Dry and very hot conditions over large parts of the country currently dominate the climate and weather news. This can have a serious negative effect on timely plantings of summer crops in the eastern production areas.
Some improvement in rainfall conditions are expected in the second week of November over the central to eastern parts of the summer rainfall area, with cooler temperatures.
Rainfall is possible over parts of the Western Cape in the last week of October. Longer-term outlooks for summer rainfall area rain are positive towards the second part of summer. – Santam Agriculture