Cumulus Report: 21 May 2019

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Warmer than normal conditions will continue over the interior during the next few days.

Unlike the previous week, some showers and thundershowers are possible over the central to north eastern interior later this week due to the movement of an upper-air trough over the area.

Without the invasion of cold, dry air over the interior, there are no current indications of severe or widespread frost. The winter rainfall region will remain mostly dry (following widespread rain earlier), but another frontal system will bring more rain to the region from Sunday (26th).

The following is a summary of weather conditions during the next few days:

• General:
o Little to no rain is expected over the interior and eastern coastal areas.
o Isolated showers or thundershowers are expected over the central to north eastern parts later this week and by the weekend. 
o The winter rainfall region should be relatively dry until Sunday (26th) when widespread rain could invade the region from the west. Widespread rain could also occur over the southern parts according to current forecasts. 
o Temperatures over the interior will on average remain normal to above normal, with largest positive deviations over the central to western interior. 
o The interior, including the maize-production areas, will remain warmer than normal. 
o There is still no indication of severe frost given the expected weather conditions during the next few days. 
o The north western interior and West Coast will become warm to hot, dry and windy from Thursday (23rd). 
o Fresh to strong south easterlies are expected over the southwestern parts by Monday (27th). 
• Rainfall: 
o Most days will be sunny and dry over the interior. 
o Isolated thundershowers are possible over the north western parts of the Northern Cape on Wednesday (22nd). 
o Isolated thundershowers are possible over the north western parts of the Northern Cape, western Free State and western North West on Thursday (23rd) and Friday (24th). 
o Isolated showers or thundershowers are possible over the north eastern interior on Friday (24th) and Saturday (25th). 
o Light showers are possible along the northern coast of KZN and along the north western escarpment on late Thursday (23rd) and Friday (24th). 
o Rain and showers are possible over the southern and southwestern parts (including the winter rainfall region) by late Sunday (26th) and on Monday (27th) according to current forecasts. With such a long lead time, forecasts are still very uncertain. 
• Temperatures:
o Hot, berg-wind conditions are possible over the West Coast from Thursday (24th). These conditions will spread to the Swartland, Karoo and Garden Route from Saturday. 
o The north western interior will remain warm to hot, dry and windy. 
o The southwestern parts of the country will become cold, wet and windy from late Sunday onwards. 
o Maximum temperatures over the western maize-production region will range between 21 and 27 °C while minimums will be in the order of 3 - 10° 
o Maximum temperatures over the eastern maize-production region will range between 20 and 27°C while minimums will be in the order of 2 - 7°C. 

Overview of expected conditions over South Africa during the next few days

Conditions in main agricultural production regions (21 - 27 May)

Maize production region: Sunny and mild to warm conditions will prevail for the most part with little to no indication of frost. On average, temperatures over the western parts will be 2 - 6 °C above the long-term mean, while the eastern parts will experience temperature closer to the long-term mean. Maximum temperatures over the western maize-production region will range between 21 and 27 °C while minimums will be in the order of 3 - 10°. Maximum temperatures over the eastern maize-production region will range between 20 and 27°C while minimums will be in the order of 2 - 7°C. Isolated thundershowers are possible over the western parts on Thursday and Friday (23rd/24th) and over the eastern parts on Friday and Saturday (24th/25th).

Cape Wine Lands and Ruens: The next few days will by dry over the winter rainfall region until Sunday. By then, another frontal system will bring widespread rain according to current forecasts. It will be cool and dry during the first few days, following widespread rain earlier. It will become warm over the entire region on Saturday and Sunday (25th/26th), but hot over the West Coast. Cloudy and cool, windy conditions will set in from late Sunday with widespread showers. Strong southeasterlies are expected in the southwest from Monday (27th). Current forecasts indicate possible heavy rain along the Garden Route by Monday - forecasts so far ahead of time are very uncertain.

Possible extreme conditions - relevant to agriculture

According to current model projections of weather conditions during the coming week, the following may be deduced:
• North westerly winds and relatively high temperatures are possible over the Northern Cape from Thursday (23rd). Where vegetation is dry, these may be conducive to the development and spread of wild fires. 
• Hot, Berg wind conditions are possible along the West Coast from Friday (24th) until Sunday (26th) and over the Eastern Cape Coast and Karoo from Saturday (25th) until Sunday (26th). Where vegetation is dry, these may be conducive to the development and spread of wild fires. 
• Cold, wet and windy conditions may set in over southwestern parts of the country later on Sunday (26th) according to current forecasts. These may impact negatively on small stock. 
• Heavy rain is possible, according to current outlooks, from Sunday evening over the Garden Route. Forecasts this far ahead of time are uncertain. 
• Fresh to strong south easterlies are possible over the southwestern parts by Monday (27th).