Seasonal climate watch

GARDEN ROUTE | KAROO NEWS - In the latest seasonal climate watch from Cobus Olivier of the South African Weather Service, we gain insight into what is happening in our area with regard to the climate.

Overview

The El Niño-Southern Oscillation (ENSO) has recently crossed the La Niña threshold and is predicted to remain on the boundary of this threshold for the next few months.

Current predictions are still uncertain, with multiple global models predicting different direction (either strengthening the La Niña state or moving back to a Neutral state.

For South Africa, caution is still advised in using the ENSO in any important planning decisions as it seems to be currently very volatile and unpredictable. For South Africa time is running out as well for a potential La Niña to affect us as summer is coming to an end.

Current predictions indicate above-normal rainfall for most of the north-eastern parts of the country during the full forecast period.

This is in stark contrast to previous predictions and is most likely due to the sudden decrease in temperatures in equatorial pacific oceans, prompting a sharp increase in probability in getting above-normal rainfall.

Below-normal rainfall is expected over the South-western parts of South Africa, however it is not their rainfall season yet, so no significant impact is expected.

Minimum and maximum temperatures are expected to be mostly above-normal countrywide for the forecast period.

However, the southern coastal areas indicate that below-normal maximum temperatures are more likely throughout the summer 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.

2. South African Weather Service Prediction System

2.1. 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 (FMA) predictions for rainfall (Figure 1) and average temperature (Figure 2)

Figure 1: February-March-April, FMA (2025) global prediction for total rainfall probabilities

Figure 2: February-March-April, FMA (2025) global prediction for average temperature probabilities

2.2. 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 January 2025 initial conditions, and are presented below (District names can be seen in the appendix indicated in Figure A4)

Figure 3: February-March-April 2025 (FMA; left), March-April-May 2025 (MAM; right), April-May-June 2025 (AMJ; 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: February-March-April 2025 (FMA; left), March-April-May 2025 (MAM; right), April-May-June 2025 (AMJ; 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: February-March-April 2025 (FMA; left), March-April-May 2025 (MAM; right), April-May-June 2025 (AMJ; 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 February-March-April, March-April-May and April-May-June 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 February-March-April (FMA; left), March-April-May (MAM; right) and April-May-June (AMJ; bottom).

Figure 7: Climatological seasonal averages for minimum temperature during February-March-April (FMA; left), March-AprilMay (MAM; right) and April-May-June (AMJ; bottom).

Figure 8: Climatological seasonal averages for maximum temperature during February-March-April (FMA; left), March-AprilMay (MAM; right) and April-May-June (AMJ; bottom)

3. Summary implications to various economic sector decision makers

Water and Energy

The expected above-normal rainfall conditions in most of the northeastern parts of the country are likely to increase water levels during the forecasted period.

These conditions may result in flash floods in flood-prone regions. Additionally, maximum and minimum temperatures are expected to be mostly above normal during the forecast period and this may result in increased demand for cooling countrywide, except for the southern coastal areas where the expected below-normal maximum temperatures are expected.

Relevant decision-makers are encouraged to take note of these possible outcomes and communicate with affected businesses and communities accordingly.

Health

The predicted higher temperatures in most parts of the country, except for the southern coastal areas, are expected to greatly increase the risk of heat exposure, potentially leading to heat stress and other heat-related health problems.

Furthermore, this rise in temperatures may increase the risk of prolonged UV exposure, which may exceed level 3 on the World Meteorological Organization's UV Index. Such heightened UV exposure could result in a higher incidence of sunburn and other UV-related health issues. Additionally, elevated temperatures may accelerate the growth of food-borne pathogens, raising the risk of foodborne illnesses.

The public is advised to maintain good food hygiene, adhere to local health guidelines under these conditions, and take necessary precautions to manage heat exposure.

The predicted above-normal rainfall for most of the north-eastern parts of the country is likely to result in flash floods, particularly in flood-prone areas and regions with inadequate drainage systems.

These conditions may increase the incidence of waterborne infections, water-related injuries, and drowning accidents, heightened by recreational water activities. It is recommended that the public take precautions and follow the advice and recommendations of local authorities. Local authorities are encouraged to monitor these risks, develop mitigation strategies, and enhance public health surveillance.

Agriculture

Above-normal rainfall is expected over most parts of the summer rainfall region, especially in the northeastern parts of the country during the late summer and autumn seasons. These above-normal rainfall forecasts are likely to have a positive impact on crop and livestock production in these areas.

However, there is an increased risk of water logging that can cause crop damage in areas receiving excessive rainfall.

Therefore, the relevant decision-makers are encouraged to advise farmers in these regions to implement soil and water conservation measures, establish effective drainage systems, proper water harvesting and storage techniques, and other appropriate farming practices.

4. 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.