SABI Magazine SABI Magazine June July 2017 | Page 44

Weather

Weather- Seasonal Climate Watch

May to September 2017

Advisory
Recommendation
There is an indication that some parts of the winter rainfall season may receive much needed abovenormal rainfall during early winter( May-June-July). However there is still a strong uncertainty and low confidence component associated with this outlook as the skill levels remain low for winter rainfall forecasts across the country. Other international centres also indicate that there is at this stage no signal that would indicate which direction the rainfall might take for the winter rainfall areas.
Temperature forecasts are inconsistent among forecasting systems, however, the majority
seem to indicate a higher chance of colder conditions to occur over the north-east of the country and warmer conditions over the south-west. At this stage there is no forecast available for the next spring and summer seasons starting around September / October 2017. The only indication of what might be in store, is from the ENSO forecast. Currently there is an expectation that an El Niño event would occur during the next spring / summer seasons. This event is usually, but not exclusively, associated with drier summer rainfall conditions.
There has been continuous indications of above-normal rainfall for the drought stricken areas in the south west of the country. Unfortunately none of those forecasts show a high degree of confidence and as such should be viewed cautiously. Due to the negative impact of drier conditions that could possibly occur, it is recommended that plans be in place to alleviate the impacts of such an event.
The next outlook for spring / summer is not favourable with regards to rainfall and the public is reminded that if El Niño does occur and exert its usual
impact, the country might once again be put under strain with regards to water resources. It is important to note, however, that the summer forecast is not available yet, so there is no indication of what impact( if any) this El Niño event might have on summer rainfall. Precautionary measures are still advised where possible, in the event that the expected El Nino event does have its usual impact. It is therefore very important to keep monitoring any developments that may provide more clarity on the current expectations for the coming seasons.
Rainfall
The forecasting system indicates a significant amount of mixed forecasts across the country. There are some indications that the winterrainfall region as well as the western interior may receive above-normal rainfall during winter, however, this system struggles with forecasts during these seasons.
Minimum and Maximum Temperatures
There is mostly an indication that the north-east of the country would experience colder conditions during winter. The south-west, however, seems to indicate that warmer conditions can be expected.
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 2017. Forecast quality for average seasonal temperature is indicated in the Appendix( Figure A2).
Figure 1: Rainfall forecasts for the three overlapping seasons valid for the period of May to September 2017 and extreme forecasts for May to July 2017 season( right panel). Forecast quality for total seasonal rainfall is indicated in the Appendix( Figure A1).
Information supplied by South African Weather Service.
For more information please contact: Cobus Olivier- Scientist: Prediction Research: cobus. olivier @ weathersa. co. za Website: www. weathersa. co. za Weatherlines: 012 367 6000 and USSD- * 120 * 7297 #
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SABI | JUNE / JULY 2017