Several cold fronts are set to sweep the country up to the end of July, and the precipitation pattern of these fronts may change in the coming weeks.
By Alani Janeke, senior journalist at African Farming and Landbouweekblad
Cold fronts, of which some may be strong and others weaker, will move across the country regularly until the end of July. The systems are forecast for around 21, 23, 25 and 26, as well as 28 July. The strongest next system is expected around 25 and 26 July, says independent agricultural meteorologist Johan van den Berg.
“Minimum temperatures will again drop sharply to below freezing, but only over the central to southern interior. It does not seem likely that it would reach the same levels of cold experienced in the first two weeks of July.”
With these systems, the likelihood of frost occurring as far afield as Limpopo also decreases significantly, he says.
“Short-term forecasts do however suggest that cold conditions, and frost may occur regularly over the central to southern interior until well into August.”
Beyond August, the frequency of cold conditions and frost will decrease, although the risk of sporadic drops in temperature and frost remains very high until October.
Changes to precipitation pattern
Weather models currently indicate that the frontal systems set to occur in the coming weeks will not be moving as far up the west coast as previous systems but will instead sweep down along the Southern Cape and across the east coast of the Eastern Cape as well as KwaZulu-Natal.
“From 24 to 27 July as well as in the first week of August, reasonably heavy rain of more than 30mm may fall over Gqeberha, and more than 20mm in George, Mossel Bay, Still Bay, East London, Coffee Bay and even Margate. Lower rainfall is expected over the interior of these regions.”
Precipitation in excess of 10mm may occur over the southwestern Cape during the same period.
Tangible temperatures
Van den Berg says very cold conditions were prevalent over the central and southern interior in the past week, with frost having occurred even in low-lying areas at George in the Garden Route over the weekend. “Tangible temperatures were also much lower compared with the recorded temperature readings.”
Tangible temperature refers to the temperature experienced by the body. A drop in temperature happens when body heat is lost through radiation and conduction, and by way of the wind drawing heat away from it. The loss of body heat may take place through clothing that conducts heat energy, yet the most heat is lost through convection, or drawn away by wind, for example. In addition, wet conditions may cause tangible temperatures to decrease even further.
“As a result, a temperature of 5°C at a wind speed of 30km/h could mean the tangible temperature drops as low as freezing. There is also the cumulative effect when exposure takes place over longer periods and the body temperature starts to drop to dangerously low levels.”
Even though “woolly” clothing helps a great deal, especially to reduce the effect of heat conduction, it is also essential to wear something that reduces the effect of heat convection or or the withdrawal of heat, like a waterproof jacket that doesn’t “breathe” and thereby doesn’t allow heat to escape, he explains.
Beware of wildfires
Fire protection associations already confirmed to African Farming at the start of winter that they were expecting a severe fire season.
With strong winds accompanying the movement of cold fronts across the country, Van den Berg says, the fire season in the summer-rainfall region is now in full swing. “There is a lot of combustible material as a result of the previous season’s very late rains, and the risk for this fire season will increase when storm conditions start to occur. Lightning may strike very quickly and over large areas, causing fires in inaccessible areas, among other places.
“Although precautionary measures such as fire breaks, extinguishers and so forth are very important, it is often essential to implement damage-control measures. Farmers are advised to consider insurance for their livestock and other property. It is even more important to ensure that the cover that is taken out is specified in the policy at the correct price and amounts, because it is vital for a farmer to be able to continue with his or her farming operation after a disaster.”
