Summary
La Nina continues but is showing a weakening trend. It is highly possible that there will be some revival in October to December before it will most probably dissipate before the winter of 2023. The Indian Ocean is also expected to be in a favourable state to support the La Nina in terms of rainfall.
Long term outlooks for the Summer Rainfall Area are for below average rainfall until about October, following by above average rainfall from about November 2022 to January 2023 (impact of both La Nina and Indian Ocean).
Rainfall conditions for the Winter Rainfall Area will be about average until October with sporadic dry spells.
Extreme cold conditions in the first week of July over the central to southern areas.
Late frost events most likely in spring and early summer.
1. Current conditions
Rain again occurred in the central, western and south-eastern Summer Rainfall Area in the second part of June. The heaviest falls were recorded in the Eastern Cape where up to 100mm occurred in the catchment areas of the nearly empty Kouga and Churchill (Krom river dam) dams supplying water to the Nelson Mandela Bay Metropole. It is however uncertain of how much water will eventually reach the storage dams due to many smaller farm dams and weirs that must be filled in the very important Langkloof fruit producing irrigation areas before reaching these larger storage dams. Falls of more than 30mm also occurred in the Northern Cape and western Free State in districts like Upington, Askham, Vanzylsrus, Kuruman, Kimberley, Vryburg, Bloemfontein and Fauresmith.
This rain in June in the predominantly grazing areas of the Northern Cape, Free State, Eastern Cape and Northwest Province are welcomed by live-stock farmers. It can assist in keeping grass and other plants green at the base and can also help in rapid recovery of production after winter once temperatures are warmer. It can also decrease the initial fire risk with higher humidity and partially green vegetation.
The summer crop harvesting process is in full swing and although some areas are still very wet and difficult to access, are yields in general average to above average except for areas that suffered water-logged conditions. According to the Crop Estimates Committee is the crop size of maize down by about 10% from the previous season.
Very heavy falls causing flooding in the Winter Rainfall Area were recorded between 13 and 15 June with for example Grabouw 149mm, Bellville 115mm, Paarl 100mm, Ceres 86mm, Malmesbury 61mm and Villiersdorp with 58mm. This rain is very significant for winter grain farmers, improving soil water conditions. It will also be beneficial to replenish water levels in storage dams, especially smaller dams where water was depleted during the dry summer.
Storage dams in the Summer Rainfall Area are still at very high levels in the last week of June with the Vaal dam at 105.5%, Bloemhof dam at 102.7%, Vanderkloof dam at 99.2% and Gariep dam at 98.8%. Western Cape dam levels increased on average by more than 5% due to the heavy rain in the third week of June and is on average at about 59.1% compared to 55.9% the same time in 2021. The Kouga dam in the Eastern Cape increased slightly to 14.2%, the Impofu dam to 10.4% and Churchill dam to 14.2% but there is still some inflow expected due to the rains in the last ten days of June.
The water level in Lake Kariba in Zambia is at about 33.4% compared to 53.2% last year the same time while the Katse dam in Lesotho is at 95.1% and the Mohale dam at 97.6%. The Hardap dam in southern Namibia was on 20 June 2022 at 67% of full volume while the largest storage dam, the Neckartal dam, at 98.3%.
2. ENSO and Indian Ocean
2.1 ENSO (El Nino Southern Oscillation)
La Nina conditions continue although it is currently showing a weakening trend. The important Nino-3.4 area saw sea surface temperatures decreased from about 1.2°C cooler than normal at the end of May to about 0.6°C cooler than normal (0.5°C cooler than normal is the cut of point between La Nina and neutral). Surface temperatures of all Nino-areas eased and is heading towards the neutral phase within the next month or two. A weak revival is expected from about the end of August until December. Current outlooks are favouring a more permanent weaking phase to start from about January 2023 to indicate the end of the current three-year-run of La Nina conditions.
It will only be the third time since 1950 that there is a three-year-spell of consecutive La Nina-conditions: 1973-1976; 1998-2001; 2020-2023. There was also a spell close to three years from 1954 to the end of 1956.
Longer term trends are indicating that the 2023/24 season will most likely predominantly be neutral with the start of a spell of El Nino- or neutral conditions from about 2024/25 until about 2027/28 or even longer.
2.2 Indian Ocean
The Indian Ocean will play a very important role to determine rainfall conditions in east and southern Africa. The Indian Ocean Dipole Index (IOD) is currently in a neutral phase, but forecasts indicate a sharp drop towards a strong negative phase from about July to at least December. (A negative IOD is indicating cooler surface water towards the western Indian Ocean (African coast) and warmer water towards Australia, as was the case in 2021). (See the impact on rainfall in the next Section (3.1 Summer Rainfall Area).
3. Rainfall and Climate Outlooks
3.1 Summer Rainfall Area
With positive rainfall signals from both La Nina and the negative phase of the IOD, are the following the most probable outcomes in terms of rainfall and temperature:
3.1.1 Limpopo, north Gauteng, northern parts of KZN and Lowveld:
Long term: Below average rainfall from July until about October but average to above average rainfall for midsummer. Probable drier conditions in the second part of summer. Frost can be expected until the middle of August over the southern parts of Limpopo and adjacent Gauteng.
Short term: Light falls of rain is possible towards the middle of July. Frost possible from about 29 June to 2 July as well as in the second week of July.
3.1.2 Southern Gauteng, Highveld of Mpumalanga, and north-eastern Free State:
Long term: Below average rainfall from July to middle of October but average to above average from October to January. Drier spell from the second part of January. Frost possible until about the first part of October.
Short term: Very little or no rain until at least the end of July. Extreme low minimum temperatures in the first week of July.
3.1.3 Northern Cape (north of Orange River), Northwest Province and central/western Free State:
Long term: Below average rainfall from July to middle November but average to above average in December and January. Drier spell from about February. The probability for late frost is again high with frost possible until about the middle of October, especially the southern parts.
Short term: Very little or no rain until at least the end of July. Very low minimum temperatures up until the first week of July but more mild conditions for the rest of July but colder again in August.
3.1.4 Eastern Free State, southern parts of KZN and northern parts of the Eastern Cape:
Long term: Rain possible over the coastal areas and adjacent interior of the Eastern Cape and KZN from about July. Very low temperatures until about the end of September.
Short term: Light rain associated with snow is possible on 2-4 July, 8 to 10 July as well as 14 to 16 July over the Drakensberg range and adjacent areas. Extreme danger for livestock.
3.1.5 Southern parts of the Northern Cape and adjacent areas of the Eastern Cape
Long term: Dry conditions from July until October/November (light falls in July). Very cold conditions still possible until at least the middle of September with frost.
Short term: Light rain with a possibility of snow over the higher lying interior. Extreme cold conditions in the first week of July.
3.1.6 Coastal areas of the Eastern Cape as well as rest of Garden Route
Long term: There is a high probability of rain from about July to September due to the impact of both La Nina and Indian Ocean. There is even a probability for flooding conditions, especially the Eastern Cape coastal areas.
Short term: There are at least three spells in July where rain can be expected with the first from about 8 to 10 July.
3.1.7 KZN interior and northern coastal areas
Long term: Rain is possible over the coastal areas from about August and can migrate later into the northern interior.
Short term: Rain is possible from about 15 to 17 July, especially the coastal areas.
3.2 Winter Rainfall Area
Long term: There is no clear rainfall signal for the Winter Rainfall Area. Current outlooks indicate about average rainfall with until about October with sporadic dry spells in between. Late frost still possible until September over lower lying areas.
Short term: Rain possible from about 2 to 8 July, especially over the Swartland, southern Winelands and Cape Metropole. Lighter falls over the South Coast and northern interior of the Western Cape.
3.3 Namibia
Not much further rain is expected for the winter and spring but average to above average rainfall is possible from about November. Temperatures will become more mild in July but cold snaps still possible in August.
Disclaimer: The author or Santam or any other parties mentioned in this document do not warrant the accuracy, completeness or reliability of any information in this document. Any actions or decisions based on the information in this document is strictly at your own risk and we will not be liable for any losses or damages in connection with the use of information stated in this document.
Johan van den Berg -Independent Agricultural Meteorologist -(M.Sc Agric, Agricultural Meteorology, UFS)
