Rainfall and other climate conditions for March
Significant rainfall occurred over parts of the drought-stricken Northern Cape and Namibia in the second part of February, but very little or no rain fell over the central to eastern parts, except for the coastal regions of KwaZulu-Natal. The summer grain crops are in a very sensitive stage and drought damage to crops started to occur over parts of the North West, central and eastern Free State and parts of Mpumalanga.
Although some parts of the Northern Cape received rain, the effect of the drought is still dominant, and it will take more time and rain to recover fully. The amount of rain received was in most cases not sufficient to replenish soil water for root development to ensure recovery. It seems that more rain fell over large parts of Namibia that can help stabilise and improve conditions.
Storage dam levels in the summer rainfall area are reacting slowly, with most of the larger dams still between 50 and 70% of full storage capacity (Gariep 76,9%, Vanderkloof 60,9%, Vaal 57,2%, Bloemhof 82,5%, and Pongolapoort 44%). Dams in Lesotho (<30%), as well as the Eastern Cape, are still critically low. The biggest cause for concern is the level of the Vaal Dam, with the end of the rainy season drawing near.
The levels of the large storage dams in the Western Cape are low to moderate (Theewaterskloof 60,9%, Clanwilliam 36,5%, and Bergrivier 80%). However, taking the time of year into account, with only three to four months before the start of the winter rainy season, the levels are acceptable and there is no reason for serious concern at this stage.
El Niño and Indian Ocean
Most of the Niño-areas are still inside the neutral range or just outside the neutral range towards El Niño, but can, in general, be seen as neutral. Forecasts still favour the neutral phase of the Niño-areas to remain for at least the winter. Although it is still very early to get a real significant indication of expected trends for 2020/21, current outlooks favour neutral (40%) or La Niña-like (40%) conditions with only a 20% probability for El Niño.
The Southern Oscillation Index (SOI), which is a measure of the coupling between surface conditions in the Niño-areas and overlying weather systems, is also in the neutral range.
The Indian Ocean Dipole (IOD) Index is also well within the neutral range, with forecasts indicating that the IOD will remain in the neutral phase for the next months.
Expected rainfall and temperature condition
Summer rainfall areas
The rainfall outlook for most of Southern Africa is negative over the short term for most of March, although there might be some improvement during the second part of March. Only light rainfall is expected over the central to eastern parts of the country in March, with the Atlantic high-pressure system that will start dominating again from the west.
The current outlook indicates a low probability (<10%) of frost before the middle of April, but there is a 20 to 30% probability that it will occur before the end of April. The most probable first date of frost is in the first two weeks of May.
More worrying is the lack of heat units and low temperatures that were experienced in the last weeks of February. However, with the low probability of rain in March it is likely that heat units will pick up again.
Winter rainfall areas
Very little or no rain is expected for most of the winter rainfall area for March and most of April, although there might be some rain in the second week of March in parts of the southern Cape coastal region.
Following weeks of rain over many parts of Namibia, the outlook for more rain in March is negative for most of Namibia, with the exception of the extreme northern parts where light falls are possible.
Summary and conclusions
Less rain occurred over the summer grain area than expected in the second part of February, with most rain concentrated towards the western parts of the country and Namibia.
Some drought damage started to occur on the maize crop in the eastern Free State, parts of Mpumalanga as well as parts of the extreme northern area of the North West. More drought damage is expected with a negative outlook for rainfall for most of March.
All the forecasting indices, namely ENSO (Niño-areas), Southern Oscillation Index (SOI) and Indian Ocean Dipole (IOD), are in a neutral state.