1. Current conditions
Better than expected rainfall conditions occurred in the second week of March 2019. The very dry central parts of the country as well as large parts of the Western Cape received falls of more than 50mm and even localised flooding with heavier falls occurred. The heavy falls of rain over the southern parts was as a result of a cut-off low that developed, drawing moisture from the tropics over the western parts of the country. Rain over the central to western summer crop areas in March was just in time or about 1-2 weeks too late to prevent drought damage. Severe damage to especially the maize crop in early reproductive stages already occurred in some parts before the rain. The current dry and hot conditions are now again started to cause drought damage to summer crops because the recharge of soil water from the rain was not sufficient to cope with the high water demand of crops now in the peak water use stages.
Drought conditions intensified over the extreme north western and western to south western parts of the country. The situation increasingly becomes serious with the winter on hand and farmers left with very little or no food for animals.
Although surface water for large irrigation schemes and storage dams in the Summer Rainfall Area is sufficient for the winter, is there a problem that starts to develop for the 2019/20 season with storage dams that were not recharged as expected with the rainy season already nearing its end. Smaller dams and farm dams already showing low levels, even for winter production. The water situation in the Western Cape is better than last year the same time with the rainy season on hand. If sufficient rainfall is not received in the next 3 tot 6 months, the situation can escalate again towards drought conditions and shortage of water.
2.El Nino and Indian Ocean
The unpredictability of El Nino continues with lower sea surface temperatures since the beginning of March 2019. Although sea surface temperatures dropped by about 0.3˚C in all the Nino-areas except for Nino1+2, are all the areas still solid in a weak El Nino state. It is too early to predict with any certainty what is going to happen during winter and especially in the summer of 2019/20 due to the volatile status of temperatures in the Nino areas during winter and early spring.
The Southern Oscillation Index (SOI) that is the measure of interaction between sea surface temperatures and climate systems, remains negative since about the beginning of February 2019 with a 30-day average value on 19 March of -12.53 (-30 = very strong El Nino and +30 = very strong La Nina).
Warming of the Indian Ocean to the east and south of Madagascar took place since the second part of February. The Indian Ocean Dipole Index (IOD) is now in the neutral phase but it is expected to change to neutral/positive in the months to come. A positive phase of the IOD is a negative signal for rainfall for Southern Africa and vice versa for the negative phase.
3. Expected rainfall and temperature conditions
3.1 Summer Rainfall Areas
3.1.1. Rainfall
The rainfall season is now rapidly coming to an end. Short term forecasts are however still indicating some rain possible in the last week of March and again in the second week of April but heavy falls are not expected to occur, especially over the central to western parts.
Expected rainfall conditions are poor over most of the western parts of the country that includes the western parts of Northwest Province, western to southern parts of the Northern Cape and western parts of the Eastern Cape.
3.1.2 Frost
The frost risk still remains high for late planted summer crops but short to medium term forecasts are showing only that temperatures below 5˚C towards to occur in the second part of April. Frost in the last two weeks of April can still cause some damage to the maize and sunflower crops.
3.2 Winter Rainfall Areas
Very little rain is expected for the next weeks over the south west Cape but light falls are possible over the southern Cape and eastern coastal areas and adjacent interior.
3.3 Namibia
It likely that very little rain will occur for the rest of the summer and autumn. Only light falls are possible in the last week of March in some areas.
4. Summary and conclusions
The rainfall event in the second week of March prevented serious drought damage to the summer crop. Rainfall amounts and spatial extent for this period exceeded the expectations and forecasts.
Short term forecasts are again negative for rainfall over the central to western parts until at least the first week of April. High temperatures and high water use by plants can cause drought damage to late planted crops.
El Nino is still present although less intense compared to the end of February. Uncertainty remains about the further El Nino development for months to come as well as for 2019/20.
Serious concerns about the drought in the western, south western and north western parts of the country to continue for another year.
Santam AGRI Johan van den Berg
