Wide spread rainfall started to occur in the first two weeks of February over large parts of the country. The heavy falls of rain of up to 100mm or more over the western and south western parts of the country, Eastern Cape as well as Namibia (especially southern Namibia) was not expected in terms of the long term rainfall forecasts. The rainfall in many areas was sufficient to alleviate drought conditions to a large extent but there are still areas where very little or no rain occurred in these areas. Drought or very dry conditions still maintains it grip on agriculture over parts of the north western, central to south eastern Free State, parts of KZN and western parts of the Northwest Province and adjacent parts of the Northern Cape.
Although significant rainfall occurred over much of the Summer Crop Area is it far from enough to ensure sufficient water to finish the crop season without drought damage and rain is urgently needed within the next two to three weeks. Without further rain in February will there certainly be drought damage in especially the central to northwest Free State, parts of KZN and smaller pockets in Northwest Province.
Grazing conditions will improve dramatically from the rain in the first part of February over much of the extensive rangeland areas. More rain is however needed to ensure sufficient dry matter production for the winter, spring and early summer but there is still about two months where production still can occur in the western areas before reduced production will set in from low temperatures.
2.El Nino and Indian Ocean
El Nino conditions remains in the neutral range (Nino1+2, Nino3 and Nino3.4 = 0.4˚C warmer) or just outside (Nino 4 = 0.8 ˚C) the neutral range.
The Southern Oscillation Index (SOI) also remained neutral.
Significant cooling of the western Indian Ocean (near Africa coastline) took place in the last month but warming is continuing in the central to northern Indian Ocean. The Indian Ocean Dipole Index (IOD) remains in the neutral range.
Short term forecasts indicating the development of a strong low pressure system over Mozambique and the adjacent Mozambique channel from about 17 February.
3. Expected rainfall and temperature conditions
3.1 Summer Rainfall Areas
3.1.1. Rainfall
It seems that the development of a strong low pressure system over Mozambique and adjacent Indian Ocean from about 17 February will again disrupt the rainfall patterns for the rest of February. It seems at this stage that the system can produce heavy rainfall over the inland areas of Mozambique and even north eastern parts of the RSA as well as Zimbabwe and even parts of Botswana. The expected track of movement of the system is still uncertain in terms of how far inland it can have an effect.
Drier conditions are again expected over the central but especially western parts of the country until at least the second week of March.
Although forecasts are very unreliable this season, are there still indications of below average rainfall for March and April.
It is however not excluded that localised smaller cut off low pressure systems may develop causing heavy rain. There is some similarity between eastern Australian climate conditions and the summer rainfall in Southern Africa. Climate extremes like flooding in northern Queensland, Australia; flooding in southern and western South America, extreme cold and snow in the northern hemisphere are all indications of highly volatile climate conditions.
3.1.2 Frost and heat units
The expected drier conditions for the rest of February and even March can assist in more heat units but increase the drought risk. Plantings of maize in the northwest Free State after the end of December 2018 is at risk for frost damage before the middle of April. The risk for damage is lower for the Northwest Province with a very low probability for damaging frost before the end of April.
3.2 Winter Rainfall Areas
Hot and dry conditions seem to be the order of the day for the next month or two. Much uncertainty about the onset of winter rainfall but the initial projections are for normal to later than normal. The remnants of El Nino type of conditions may improve the probability for rain. If El Nino strengthen in months to come can it enhance rainfall conditions.
3.3 Namibia
Rainfall conditions remain negative for the next months for the southern and western parts but can improve in the second week in March for the central to northern parts.
4. Summary and conclusions
Significant falls of rain occurred over much of the Summer Rainfall Area but follow up rains over the central to western and southern parts seems to be lacking due to the expected presence of a tropical low pressure system over Mozambique.
Heavy falls are possible over the north eastern parts in the second part of February as a result of the tropical low pressure system over Mozambique.
Both El Nino and Indian Ocean Dipole Index (IOD) are in neutral phases. There is still a more than average probability for El Nino to show some signs of redevelopment.
Johan van den Berg. Santam
