1. Current conditions
Following the wide spread rain in the first part of February 2019, dry and hot conditions once again set in for large parts of the country, especially over the central to western parts. Forecasts for follow up rain towards the end of February and first part of March did not realise. Although crop conditions are better towards the eastern production areas, is the situation very critical for the rest of the summer crop area and deteriorate daily. The middle part of March this year will coincide with the very sensitive reproductive stages of the very late planted summer crops. Current as well as expected hot and dry conditions for the rest of March can seriously impact on especially the maize and sunflower crop.
A series of tropical low pressure systems over Mozambique and adjacent Indian Ocean as well as a tropical cyclone to the east of Madagascar dominates the weather patterns, resulting in corresponding high pressure systems dominant over the interior of Southern Africa.
2. El Nino and Indian Ocean
El Nino started to redevelop since January 2019. All the Nino areas except Nino1+2 are now solid in an El Nino state (> 0.5˚C warmer than average). (Nino-1+2 = +0.4˚C, Nino-3 = 1.0˚C; Nino3.4 = 1.1˚C and Nino-4 = 1.1˚C warmer).
The Southern Oscillation Index (SOI) that is the measure of interaction between sea surface temperatures and climate systems now for the first time this season started to react and the 30-day average value was on 5 March 2019 = -14.1. (-30 = very strong El Nino and +30 = very strong La Nina).
It is still too early to speculate about the status of the Nino-areas for the 2019/20 season because the March to August period is usually a very unstable period in terms of the Nino sea surface temperatures.
The Indian Ocean Dipole Index (IOD) moved into the negative phase but it is expected to change to neutral/positive in the months to come. A positive phase of the IOD is negative 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
Drier conditions remain dominant since the second part of February over the central to western, north western and southern parts of the country. Forecasts seem to remain negative for significant rainfall and it looks that drought conditions will remain and intensify over the central, south western, western and north western parts of the country.
3.1.2 Frost
The frost risk still remains high for late planted summer crops but short to medium term forecasts are showing only a possibility of temperatures below 5˚C towards the end of April.
3.2 Winter Rainfall Areas
Moderate temperatures are expected with an increased probability for rain, especially towards the southern Cape for the next weeks.
3.3 Namibia
Rainfall conditions remain negative for the next months for the southern and western parts but can improve somewhat in the second week in March for the central to northern parts. Overall is it likely that very little rain will occur for the rest of the season.
4. Summary and conclusions
Production conditions deteriorated over most of the central to southern and western interior. Most of the summer grain crop is now in a very critical development stage and drought damage is already occurring
Short term forecasts are showing some light falls of rain of less than 20mm for the period 8 to 11 March. Higher amounts are possible over the eastern to south eastern parts of the country for this period.
El Nino is now in a redevelopment phase and most of the Nino-areas exceeded the limits to be classified as El Nino. Uncertainty remains about the further El Nino development for months to come as well as for 2019/20.
Rainfall conditions deteriorated for the rest of the summer season for most of the Summer Crop Area.
Johan van Den Berg Santam
