Weather
Weather- Seasonal Climate Watch
May to September 2016
Advisory
Current observations still show the continuation of El-Niño. As most ENSO( El-Niño Southern Oscillation) prediction models indicate, however, there is a possibility for the development of a La-Niña toward late spring through to the coming summer season. Despite conditions over the South-western Atlantic Ocean that
may be conducive for winter type rainfall and cooler temperatures over South Africa, the forecast signal is dominated by a huge uncertainty for the rainfall and temperature forecast in the coming seasons.
Recommendation
The likelihood of climate conditions for the
coming winter season is overshadowed by the growing uncertainty in the forecast.
Therefore, it is highly recommended that medium- and shorter-range weather forecasts be monitored for the development of conditions that may alter or strengthen the expectation of the current forecast.
Rainfall
The forecasting system favours a tendency of( well) below-normal rainfall for the early winter over most parts of South Africa( Figure1) with marginal confidence( Figure A1). Despite the large uncertainty in the forecasting system, there are chances for above-normal rainfall conditions over most parts of the country for the winter season.
Minimum and Maximum Temperatures
Minimum and maximum temperature forecasts remain largely uncertain( Figure 2) which suggests the weakening of the extreme hot condition that has been grabbing the country since late last year due to the strong 2015 / 16 El-Niño episode.
For improved confidence in a probabilistic prediction use is made of skill scores most notably the Relative Operating Characteristic( ROC) which indicates the ability of the forecasting system to distinguish events from non-events. As noted earlier, areas of ROC scores above 0.5 may be considered as areas of added confidence for the prediction( Figure A2).
For improved confidence in a probabilistic prediction use is made of skill scores most notably the Relative Operating Characteristic( ROC) which indicates the relative performance of the prediction system. Areas of ROC scores above 0.5 may be considered as areas of added confidence for the prediction( Figure A1).
Figure 2: Probabilistic minimum( left panel) and maximum( right panel) temperature forecasts for the three overlapping seasons valid for the period of May to September 2016.
Figure 1: Rainfall forecasts for the three overlapping seasons valid for the period of May to September 2016 and extreme forecasts for May to July 2016 season( right panel).
Information supplied by South African Weather Service. Enhanced Probabilities is considered to be more than 45 % probability for a specific category. If there are areas that do not show an indication of more than 45 % probability, then the forecasts for that area is considered to be uncertain.
For more information: email cobus. olivier @ weathersa. co. za Weatherlines: 082 162- * 120 * 555 * 3- 083 123 0500
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SABI | JUNE / JULY 2016