Important Issues
Short term rainfall forecasts (December) are positive but the effect of El Nino only expected in the second part of summer. Still remains a high drought risk season, especially towards the western areas.
1. Current conditions
Agricultural conditions are still on the edge of disaster in many areas. Summer crop plantings in Mpumalanga were mostly completed but in many areas also very late. Rain is needed to ensure that the crop is well established. Most of the Eastern Free State did not receive rain in time and it is estimated that less than 50% of the area is planted in time. The last recognised date for maize to emerge in this area is in the first week of December to ensure that sufficient heat units are available to complete the growing cycle.
Very little plantings were possible in the central to western summer crop production areas except for an area from Koppies, Parys and Potchefstroom to Ventersdorp where planting rain occurred. Although the planting window is still “open” until the last week of December for the western production areas, are primary cultivations not yet completed. Rain is therefore needed to first cultivate fields and then to plant, putting pressure on the time available before it is too late.
It must however be stated that in some areas are the soil water conditions in deeper layers of the soil profile relative favourable but the top layers are dry. At least 50mm to 100mm is needed in most areas to plant (central to western production areas) and eastern production areas to prevent drought damage within the next weeks.
2. El Nino and Indian Ocean
Sea surface temperatures in the Nino3.4 area (and all the other Nino-areas) exceeded the 0.5°C above average limit since the start of October. There is still however very little or no coupling with the atmosphere considering the Southern Oscillation Index (SOI) as indicator. The SOI is still in the neutral phase towards the La Nina side for the 30-day average value. Some other variables regarding El Nino are important like when the peak will be reached and will the period of be long enough to be classified as El Nino?
The Indian Ocean Dipole Index (IOD) now moved back from the positive phase to the neutral phase that is less negative for rainfall conditions over Southern Africa. It can help to soften the effect of El Nino.
3. Expected rainfall and temperature conditions
3.1 Summer Rainfall Areas
Short term forecasts indicate improved probabilities for rainfall over most of the Summer Rainfall Area for the period 7 to 10 December as well as for the last two weeks of December. The best probabilities for rain are concentrated towards the drought stricken northern and north eastern parts of the country of Gauteng, Limpopo and Mpumalanga. Good falls are also possible over most of the Free State, Northwest, Eastern Cape and KZN. Less rain is expected in the other drought stricken areas of the central to western parts of the Northern Cape and Northwest Provinces but probabilities increase for the second part of December over those two areas with lighter falls expected.
There are three scenarios in terms of the current season forward with estimated probability of occurrence:
Weaker than expected rainfall for December and January as well as last part of the summer season (February to April) when the effect of El Nino will come into play. (30% probability)
Good rainfall in December and January with very dry conditions in the last part of the season with the effect of El Nino. (50% probability)
El Nino reaction not typical. Good rainfall for rest of the season. (20% probability)
The different scenarios will also be more valid for specific geographical areas with the western areas leaning more towards Scenario 1 and the eastern areas leaning more towards Scenario 3.
3.2 Winter Rainfall Areas
Some light falls of rain still possible with cold fronts still visiting the southern tip of the country.
3.3 Namibia
Improved probabilities for rain in the second part of December but there is a high risk for drier conditions in the second part of the summer season.
4. Summary and conclusions
Rainfall and agricultural conditions at the end of November poses reason for concern for both summer crop production and livestock grazing conditions.
Although short term rainfall forecasts are positive for rain over the Summer Rainfall Area, is good falls probably more likely over the central to northern parts of the country but weaker over the western parts.
Uncertainty about the effect of El Nino later in the season.
Johan van den Berg Santam AGRI
