Johan van den Berg Santam Agriculture
Important Issues
Nino-areas as well as Indian Ocean Dipole Index are neutral, indicating little interference with normal climate conditions for pre-winter.
Maize crop production conditions are very favourable. Records yields possible in the central to western production areas.
Average to above average rainfall is expected for the drought stricken areas of the Northern and Eastern Cape as well as Namibia in the February to April period.
1. Current conditions
Good falls of rainfall occurred since the beginning of 2020 but especially in the first part of February 2020. The rain expanded also to parts of the drought stricken Eastern Cape and well as adjacent parts of the Northern and Western Cape, leaving only the central, western and south western parts of the Northern Cape still without any rain. The timing of the rain in the first part of February 2020 was very important in terms of grain and especially maize production because most of the grain is in the sensitive late vegetative or early reproductive stages.
Current soil moisture conditions can ensure already at least an average maize crop. If favourable conditions continue for February, a record maize crop is very possible. Although some areas are experiencing water logged conditions, are these areas insignificant relative to the total crop. The nature of rainfall events with thunder storms followed by hot and sunny conditions is also very conducive for production conditions. Heavy falls of rain also ensure that deeper layers of the soil profile are replenished.
Levels of storage dams in the Summer Rainfall Area are still reacting slowly to the rain with most of the larger dams still between 50% and 70% of full storage capacity (Gariep 71%, Vanderkloof 60%, Vaaldam 57%, Bloemhof 77% and Pongolapoort 44%). Dams in Lesotho (<30%) as well as the Eastern Cape are still critically low. Large storage dams in the Western Cape like Theewaterskloof with 63%, Clanwilliamdam with 45% and Bergrivierdam with 84%, is low to moderate but taking the time of the year into account with only 3 to 4 months before the start of the winter rainy season is it acceptable and not a reason for serious concern at this stage.
2.El Nino and Indian Ocean
The majority of the Nino areas are still inside the neutral range (between 0.2˚C and 0.5˚C above average). Forecasts still favour a neutral phase of the Nino-areas to remain for the rest of the summer season.
The Southern Oscillation Index (SOI) that is a measure of the coupling between surface conditions in the Nino-areas and overlying weather systems, now for the first time since about December 2018 is showing non-El Nino like patterns. The SOI was at the end of January 2020 in a rapidly rising phase according to the Australian classification system, indicating a swing away from El Nino-like conditions to more neutral conditions.
The Indian Ocean Dipole (IOD) Index is now for the first time since about May 2019 not in the positive phase but well within the neutral range. (A positive phase is negative for rainfall). Forecasts indicate that the IOD will remain in the neutral phase for the next months.
3. Expected rainfall and temperature conditions
3.1 Summer Rainfall Areas
3.1.1. Rainfall
The rapidly rising phase of the Southern Oscillation Index (SOI) during January 2020 is significant, especially for this time of the season. A rapidly rising phase in January is usually associated with at least average rainfall over the central to western parts of South Africa as well as Namibia for the February to April period. It is therefore likely that rainfall will shift away from the eastern parts of the country to become drier to the east with improved rainfall conditions over the western parts of the country.
Short to medium term forecasts indicate that rainfall conditions will improve again in the second part of February, especially over the central to western parts as well as south eastern parts of the country (Eastern Cape and southern parts of KZN) and adjacent areas. It is most likely that the drought stricken areas of the Northern Cape will receive some rain before the end of February. Further rain is also very probable over most of the summer grain areas before the end of February but will start to weaken towards the extreme eastern parts.
3.2 Winter Rainfall Areas
Light falls of rain is possible for the short term (14 to 20 February) from thunderstorm activity. It is however very likely that the winter rainfall season will start later than normal because it is expected that summer rainfall will remain prominent for the next months. It is however very likely that further summer rainfall will occur due to forecasts of rain over the western parts of the country.
3.3 Namibia
Outlooks for rain for the drought stricken parts of central to southern Namibia are positive for the next months before winter.
4. Summary and conclusion
Timing and amounts of rain that occurred since the beginning of the year are very positive to result in a very good maize crop. Further rain that is expected in February can prevent any drought damage but smaller areas can suffer from water logged conditions.
The Southern Oscillation Index (SOI) that is a measure of coupling between the Nino-areas and with overlying weather systems, was in a rapidly rising phase in January 2020. The rising phase in January is usually associated with at least average rainfall over most of the central to western parts of the country in the pre-winter period. The Indian Ocean Dipole Index is also now settled in the neutral phase.
Short to medium term forecasts indicates relative high probabilities for rain towards the second part of February for large parts of the country.
