Weather update: Cut-off low causing adverse weather over South Africa

JULY 25, 2016

A cut-off low has developed over the western parts of the country and a surface high pressure is extending into the eastern and north-eastern parts (see fig. 1). Significant amounts of rain have already been reported over the eastern and south-eastern parts, with heavy rain (50mm or more in 24 hours) reported along the south coast and adjacent interior of KwaZulu-Natal.

Paddock recorded 83.2mm, Durban 54.8mm, Mount Edgecombe 63.4mm and Margate 69.6mm. Due to a significant drop in freezing levels, snowfalls have already been reported in places over the south-western parts of KwaZulu-Natal and north-eastern parts of the Eastern Cape, with significant amounts in some places and reports of road closures.

The cut-off low is expected to intensify over the western parts of the country today (Monday 25th July 2016). This will result in further cold to very cold, wet and windy conditions over most parts of the country. Showers, rain and thundershowers are expected over the central north-eastern and eastern parts of the country, spreading to the southern parts from the afternoon and into the evening (see fig. 2 below).

Heavy rainfall, leading to localised flooding, is expected over the central and south-eastern parts of the country as well as over the southern parts of the Western Cape from this evening. Snowfalls are expected to continue over the eastern and south-eastern interior, with some light snowfalls on the eastern mountains of the Western Cape (see fig. 3 below).  

This cut-off low is expected to move slowly southwards and then south-eastwards tomorrow (Tuesday 26th July) and into Wednesday (27th July), exiting off the Eastern Cape coast by Thursday evening (28th July).  The precipitation
is thus expected to continue into tomorrow (26th July) and will include the western parts of the country as well.

Heavy rain, leading to localised flooding, is expected over the central, south-eastern and south-western parts of the country (see fig. 4 above). Snowfalls are also expected to continue over the south-eastern and southern interior as can be seen in fig. 5 above.

Due to a conducive environment, severe thunderstorms, with hail and damaging winds, may develop over the central interior today (25th July) and tomorrow (26th July). Along the south-east and extreme south-west coast, gale force winds are expected from tonight, while high seas are possible in places along the south and east coast tomorrow. Storm surges are also possible along the extreme south-west coast tomorrow.

By Wednesday (27th July), conditions are expected to start clearing over the central parts as well as in the north-east from the afternoon as the cut-off low moves further south. The remaining parts of the country will start clearing from Thursday as the cut-off low exits off the Eastern Cape coast by the evening.    

Current alerts issued by the South African Weather Service:

Warnings:

  1.  Heavy rain leading to localised flooding is expected today (25th July) in places over the eastern and central parts of the Eastern Cape, the central and western parts of the Free State, central parts of the North West Province, the coast and extreme southern parts of KwaZulu-Natal as well as the south coast and adjacent interior of the Western Cape from this evening. This is expected to persist over the eastern parts of the Eastern Cape, central and eastern parts of the Free State, Gauteng, the coast and southern parts of KwaZulu-Natal as well as the south-western and southern parts of the Western Cape tomorrow (26th July).
  2.  Disruptive snowfalls are expected over the south-western and western high grounds of KwaZulu-Natal, the northern high ground of Eastern Cape and the eastern and southern parts of the Free State today (25th July). This is expected to persist over the extreme south-western parts of KwaZulu-Natal, north-eastern parts of the Eastern Cape as well as the extreme eastern parts of the Free State tomorrow (26th July).
  3.  Gale force easterly to north-easterly wind (65 – 75km/h) is expected between Cape St. Francis and Port Edward from this evening (25th July) and into tomorrow morning (26th July) but south-easterly between Table Bay and Stilbaai from tomorrow (26th July), moderating from tomorrow afternoon.
  4.  High seas, with wave heights 6 to 9m, are expected in places between Cape Agulhas and Durban on Tuesday (26th July), subsiding on Wednesday morning.
  5.  Storm surge and/or destructive coastal waves are expected between Cape Point and Stilbaai tomorrow (26th July).

Watches:

  1.  Severe thunderstorms with possible hail and damaging winds are expected over the central parts of the Free State, Gauteng as well as the central and eastern parts of the North West Province today (25th July) and tomorrow (26th July).

What can a responsible person do in order to remain safe during this event?  

Due to the extreme and persistent nature of this event, the general public is strongly urged not to venture into snowy areas on sightseeing, leisure trips. There is a distinct risk of becoming trapped in one’s vehicle and facing the danger of hypothermia. At the very least, snowy, icy conditions dramatically raise the risk of serious vehicle accidents. Outdoor hiking or climbing in the above-mentioned snow-affected regions should not be undertaken under any circumstances, even if one is experienced.

In case of heavy rain and flooding, if possible stay indoors and off the roads, avoid crossing rivers and swollen streams where water is above your ankles. NEVER drive on a road covered by water. You do not know how deep it is or if the road has been washed away. Be especially cautious at night when it's harder to recognize flood dangers.

In case of severe thunderstorms, if outdoors, seek shelter immediately but DO NOT seek shelter under a tree, under telephone and/or power lines, on hilltops, in isolated sheds, under unprotected gazebo’s or picnic shelters.

The South African Weather Service will continue to monitor further developments during this period and will issue subsequent updates as required. Furthermore, the public is urged to regularly follow weather forecasts on television and radio. Updated information may also be accessed on www.weathersa.co.za as well as via the SA Weather Service twitter account @SAWeatherService