GARDEN ROUTE | KAROO NEWS - The El Niño-Southern Oscillation (ENSO) is currently still in a Neutral state and is predicted to weaken further.
However current predictions are mixed in whether it will weaken towards a La Niña state during our next summer season.
It is advised to monitor the ENSO system, as significant changes in the system may occur after the winter period due to increased prediction skill.
We are still in the winter period; however, the current forecasts include those for the spring and early summer seasons.
With a potential La Niña event on the horizon to affect the next summer season and early indications of above-normal rainfall over most of the summer rainfall areas during Oct-Nov-Dec (OND), the initial outlook is positive for good rainfall in summer.
There is an exception however for the Limpopo region which still indicates below-normal rainfall that can be expected going into the early summer period.
Mostly drier conditions are still expected over the country during spring. Minimum and maximum temperatures are expected to be mostly above-normal countrywide for the forecast period.
The SAWS will continue to monitor the weather and climate conditions and provide updates on any future assessments that may provide more clarity on the current expectations for the coming season.
South African Weather Service prediction system
Ocean-Atmosphere Global Climate Model
The SAWS is currently recognised by the World Meteorological Organization (WMO) as a Global Producing Centre (GPC) for Long-Range Forecasts (LRF). This is owing to its local numerical modelling efforts, which involve the coupling of both the atmosphere and ocean components to form a fully interactive coupled modelling system, named the SAWS Coupled Model (SCM).
The SCM is a first of its kind in both South Africa and the region.
Below are the first season (ASO) predictions for rainfall (Figure 1) and average temperature (Figure 2)
Figure 1: August-September-October, ASO (2024) global prediction for total rainfall probabilities
Figure 2: August-September-October, ASO (2024) global prediction for average temperature probabilities
Seasonal Forecasts for South Africa from the SAWS seasonal prediction system
The above-mentioned global forecasting systems’ forecasts are combined with the GFDL-SPEAR and COLA-RSMAS-CCSM4 systems (part of the North American Multi-Model Ensemble System) for South Africa, as issued with the July 2024 initial conditions, and are presented below (District names can be seen in the appendix indicated in Figure A4):
Figure 3: August-September-October 2024 (ASO; left), September-October-November 2024 (SON; right), October-November, December 2024 (OND; bottom) seasonal precipitation prediction. Maps indicate the highest probability of the above-normal and below-normal categories.
Please refer to appendix Figure A1 for forecast skill levels.
Figure 4: August-September-October 2024 (ASO; left), September-October-November 2024 (SON; right), October-November, December 2024 (OND; bottom) seasonal minimum temperature prediction. Maps indicate the highest probability of the above normal and below-normal categories. Please refer to appendix Figure A2 for forecast skill levels.
Figure 5: August-September-October 2024 (ASO; left), September-October-November 2024 (SON; right), October-November, December 2024 (OND; bottom) seasonal maximum temperature prediction. Maps indicate the highest probability of the above-normal and below-normal categories.
Please refer to appendix Figure A3 for forecast skill levels.
2.3. Climatological Seasonal Totals and Averages The following maps indicate the rainfall and temperature (minimum and maximum temperature) climatology for the August-September-October, September-October-November and October-November-December seasons.
The rainfall and temperature climates are representative of the average rainfall and temperature conditions over a long period of time for the relevant 3-month seasons presented here.
Figure 6: Climatological seasonal totals for precipitation during August-September-October (ASO; left), September-October, November (SON; right) and October-November-December (OND; bottom).
Figure 7: Climatological seasonal averages for minimum temperature during August-September-October (ASO; left), September-October-November (SON; right) and October-November-December (OND; bottom)
Figure 8: Climatological seasonal averages for maximum temperature during August-September-October (ASO; left), September-October-November (SON; right) and October-November-December (OND; bottom).
Summary implications to various economic sector decision makers
Water and Energy
The anticipated below-normal rainfall during the ASO period, coupled with above-normal temperatures across the forecast periods, is likely to increase water losses and reduce water storage levels through evapotranspiration and drought, among other factors.
The notable indications of above-normal rainfall over most of the summer rainfall areas are likely to provide a good opportunity for water reservoirs’ recharge, although the impact might not be significant due to the experienced prolonged dry conditions over the regions.
Minimum and maximum temperatures are expected to be mostly above-normal countrywide during the forecast period and this will likely increase demand for cooling. Relevant decision-makers are encouraged to take note of these possible outcomes and communicate with affected businesses and communities accordingly.
Health
The predicted above-normal minimum and maximum temperatures across South Africa are likely to result in increased exposure to high solar ultraviolet radiation (UV) and elevated temperatures, which may lead to UV and heat-related illnesses. Relevant decision-makers are encouraged to advise the public on sun protection measures to mitigate overexposure by staying in the shade, applying sunscreen, and wearing protective clothing, especially during peak UV hours at noon.
Additionally, below-normal rainfall expected over most of the country during the spring season may cause health problems related to dry conditions.
However, above-normal rainfall expected during the early summer season in most parts of the summer rainfall regions may increase the risk of flash floods, particularly in flood-prone regions and areas with inadequate drainage systems.
These wet conditions could also contribute to waterborne infections, water-related injuries, and accidents. Members of the public are advised to take precautions and follow the guidance and recommendations of local authorities.
Agriculture
Below-normal rainfall is forecasted for most parts of the country in the early spring and mid- to latespring seasons, with the exception of some areas in the Free State Province.
Conversely, above-normal rainfall is expected in most parts of the summer rainfall regions, except for the Limpopo Province, during the early summer season (OND).
This above-normal rainfall forecast for these summer rainfall regions will likely have a positive impact on crop and livestock production. However, below-normal rainfall is predicted over the Limpopo region during the early summer period. Therefore, it is recommended that the relevant decision-makers advise farmers in this region to implement soil and water conservation measures, proper water harvesting and storage techniques, establish effective drainage systems, and adopt other appropriate farming practices.
This forecast is updated monthly, and users are advised to monitor the updated forecasts, as there is a possibility for them to change, especially the longer lead-time forecasts.
Moreover, farmers are advised to keep monitoring the weekly and monthly forecasts issued by the SAWS. Farmers are also advised to keep on monitoring advisories from the Department of Agriculture and make changes as required.
Contributing institutions and useful links
All the forecasts presented here are a result of the probabilistic prediction based on the ensemble members from the coupled climate model from the SAWS and two models from the NMME.
Other useful links for seasonal forecasts are:
• Latest predictions from the SAWS for the whole of SADC
• ENSO predictions from various centres
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