Winter Highveld temperatures
The dramatic drop in the share price of Mr Price together with comments from Woolworths and others has illustrated the mildness of the winter in parts of Southern Africa and Australia. With El Niño possibly mutating into an La Niña the stage seemed set for a colder South African Highveld winter but the figures below of the number of days within each temperature band for the roughly winter months June through August show this wasn’t the case. For both 2015 and 2016 June and July had milder nights but slightly cooler days , a feature of a less dominant high pressure system over the sub-continent and a consequent influx of air with somewhat more moisture than normal, though still quite dry. This moisture hinders both inward and outward radiation and results in smaller daily ranges of temperature. The two years’ Augusts in contrast did have dry air, allowing afternoon temperatures to reach levels not occurring in 2014. [The slightly moister conditions in 2016 resulted in 35mm of rain in the three months compared to 11 in 2015 and 7 in 2014 but still negligible, as is the norm.]
|-8 to -6||2||–||–||–||–||–|
|-5 to -3||8||–||2||–||–||–|
|-2 to 0||30||–||19||–||18||–|
|1 to 3||32||–||36||–||42||–|
|4 to 6||17||–||20||–||29||1|
|7 to 9||3||–||13||–||3||1|
|10 to 12||–||3||2||1||–||1|
|13 to 15||–||6||–||8||–||4|
|16 to 18||–||6||–||10||–||16|
|19 to 21||–||28||–||28||–||35|
|22 to 24||–||41||–||24||–||22|
|25 to 27||–||8||–||11||–||5|
|28 to 30||–||–||–||9||–||6|
|31 to 33||–||–||–||1||–||1|
Climate. The Columbia University’s Earth Institute’s International Research Institute for Climate and Society has produced a forecast for Africa for September to November indicating a 50% probability of above average temperatures for South Africa, especially for the extreme SW and extreme NE. Their forecast for December through February is similar but with a slightly smaller probability. This is despite their July 2016 discussion document saying:
“The IRI has prepared this experimental Climate Outlook for Africa for August 2016 – January 2017. Of relevance in the preparation of this outlook is a likelihood that the central and eastern tropical Pacific SSTs will be near to slightly below average during the first forecast period, cooling to become somewhat more below average for the second, third and fourth periods. By the third period, borderline to weak La Nina conditions are predicted. The cooling will be limited mainly to the eastern tropical Pacific, with the central tropical Pacific remaining near to just slightly below average.”
Bear in mind that below average SSTs (sea surface temperatures) for the eastern topical Pacific are normally indicative of El Niño having reversed. IRI describes the South Africa temperature expectations for all four three month forecast periods commencing September, October, November and December as “at least moderately enhanced probability (45 to 50%) for above normal.” The other 55 to 50% encompasses both near normal and below normal.
Australia’s Bureau of Meteorology currently has a La Niña watch which in its terminology indicates there is approximately a 50% chance of La Niña developing in 2016, or about twice the normal likelihood.
Despite what seems like good rains from time to time over the roughly four months since the last report, spanning the rainy season for the Cape and dry season over much of the rest of the country, dam levels are typically a quarter lower than a year ago. Some points of interest:
- The Free State dams have held steady over the last three months but the Lesotho feeder dams have declined sharply. Government and the media tend to concentrate on Vaal Dam levels, no doubt to alarm us, when in fact the total available for Gauteng has not declined to the same extent, with Vaal Dam purposely and for good reason being allowed to take the initial pressure.
- The levels of Eastern Cape dams which held up well into 2015 are now dropping.
- Western Cape dams have dropped less than the average over the past year but 61% of capacity close to the end of the rainy season is still unsatisfactory if levels again decrease by 20% points over the dry season. Theewaterskloof, which has about a quarter of the W Cape capacity, has fallen from 99 to 52% capacity over roughly two years.
- kZN, Limpopo and Mpumalanga dam levels have all dropped by close to one third over the past year.
- The total fall in dam levels for SA and Lesotho is one quarter over the past year.
- Gauteng’s water position is looking increasingly fragile. The Polihali Dam in Lesotho is still at least eight years from supplying water, the first phase of the Lesotho Highlands Water Project was dogged by problems, including bribes being paid, which does not bode well for the second phase, and acid mine drainage treatment is well behind schedule. With no immediate end to the drought in sight, and dam levels low, the prospects are not good for the province.
|Free State total||15,971||55||54||75|
|W Cape total||1,853||61||31||68|
|Albert Falls Dam||288||26||33||55|
|E Cape total||1,826||66||72||79|
|Katse / Mohale (Lesotho)||2,376||40||51||63|
|Total RSA and Lesotho||31,913||54||55||72|