El Nino is still present but strong indications that it will convert into more neutral sea surface temperatures. This is positive for mid to late summer rainfall for Summer Rainfall Area. Favourable rainfall conditions for most of the Winter Rainfall Area likely to remain until September, especially the western and south western parts.
1.Current conditions
Relative mild conditions over most of the Summer Rainfall Area is still present for this time of the year with below average numbers of frost and very cold days. Very little or no rain occurred but that is normal for this time of the year. More irrigated and dryland wheat is planted in the central parts of the country due to very good water availability from surface water resources and stored water for dry land production in the rooting zone as a result of the above average rainfall in late summer and autumn. The harvesting process of the maize crop in the western Free State and Northwest Province is delayed compared to previous years. It is expected that the harvesting of maize will only be completed towards the second part of August which is about 2 to 4 weeks later than normal. Most of the sunflower, sorghum and soya beans are harvested.
Grazing conditions in the western parts of the Northwest Province, most of the Northern Cape with the exception of the eastern parts, parts of the Eastern Cape and smaller parts of the adjacent Western Cape as well as smaller areas in Limpopo, are still suffer disaster drought conditions. In some of these areas is the drought conditions already present since 2012.
Conditions improved for large parts of the Winter Rainfall region with regular rainfall events since the last part of May 2019. The West Coast areas as far north as close to the Namibia border received some rain although the interior to the east still remains dry. Conditions for winter crops in the important Swartland and Southern Cape are very favourable. Dam levels also improved with the Clanwilliam dam where there was serious concern now also saw improvements.
2. El Nino and Indian Ocean
Sea surface temperatures in all the Nino-areas now reaching more regularly the neutral phase of ENSO (away from El Nino). Three of the four Nino-areas were within the +0.5˚C and -0.5˚C range on 15 July 2019. Cooler water from deeper layers now replacing warmer surface waters. Although there is a lack of consensus of most global forecasts about the future El Nino status, is it significant that changes in temperatures now start to occur. It seems that the forecast for neutral conditions now exceeds the probability for El Nino for the summer season of 2019/20.
The Southern Oscillation Index that is the measure of coupling between surface and weather systems, is still in a strong El Nino like pattern. There is usually a lag time and is it expected that El Nino type of weather patterns may still govern for the next few months.
Warming of the western Indian Ocean resulted in the development of a positive Indian Ocean Dipole Index (IOD). This is not good news for the next months for the Summer Rainfall Area, especially for spring and early summer rainfall. Forecasts however showing a weakening towards November.
3. Expected rainfall and temperature conditions
3.1 Summer Rainfall Areas
3.1.1. Rainfall
The winter period is traditionally very dry and current outlooks also indicate a low probability for winter rainfall, especially the central to northern parts. With the development of a positive IOD (Indian Ocean Dipole) for the next months can it have a negative effect on the probabilities for rain in spring and early summer. The outlook that favours a more neutral state of ENSO (away from current weak El Nino levels) can favour mid to late summer rainfall but also reduces the chances for spring and early summer rain. It is possible that spring rain may occur over the southern parts of the Summer Rainfall Area as a result of the El Nino lag effects.
3.2 Winter Rainfall Areas
Cold fronts now regularly produces rainfall over the western and south western parts of the Western Cape and even the western coastal areas of the Northern Cape. This is likely to continue for the next weeks until September. Good falls is expected in the last week of July and first part of August.
3.3 Namibia
It is likely that very little rain will occur for the next months and with a possible late start of the summer rainfall season of 2019/20.
4. Summary and conclusions
Although very early in the season are there positive indications that the current El Nino event will change to more neutral conditions in the late winter and spring months. This can have positive effects on mid- to late summer rainfall.
The Winter Rainfall Region also seems to have a good season over most of the area and further rain is expected that can lead to very good winter crop yields in especially the Swartland and surrounding areas.
