Weather outlook remains murky
The 2018/19 season will probably be remembered as one of the most difficult seasons in terms of rainfall forecasts, according to weather experts.
17 January 2019 | Weather
Although there are indications for improved chances of rain for the next week, weather experts say the long-term outlook for the summer remains less certain, and at worst, highly unfavourable, which will impact livestock grazing conditions.
A report issued by Johan van den Berg, a climatologist at Santam Crop Insurance in South Africa, states that the “uncertainty about rainfall for the rest of the summer season remains high”, not only for parts of South Africa but Namibia too.
In early January, Namibian Sun quoted Van den Berg, who especially warned farmers in Namibia to guard against optimistic hopes for a wet rainfall season. He said they should instead prepare for dry months ahead.
“Should it turn out differently, they should see that as a bonus and not the other way around.”
In a new report on climate and agricultural conditions released on 11 January, he the “2018/19 season will probably be remembered as one of the most difficult seasons in terms of rainfall forecasts”, due to a number of issues.
The report states that for Namibia and parts of South Africa, short-term forecasts are showing improved probabilities for rainfall from 15 to 23 January, but warned “there is a very high level of uncertainty about expected rainfall for the rest of the summer season”.
The report highlighted two possible scenarios in terms of the current season going forward - the first being a 70% probability of average rainfall for the rest of January and the first part of February, with dry conditions in the last part of the season, when the El Niño effect comes into play.
The report states that the conditions contributing to the difficulty in forecasting rainfall for the rest of the season is partly due to a “very volatile set up of sea surface temperatures in both the Indian and Pacific oceans”.
El Niño conditions in terms of sea surface temperatures exceeded limits only in October 2018, following forecasts of much earlier development, the report notes.
As a result, by the end of December there was still no coupling of El Niño and weather systems, with the Southern Oscillation Index still on the La Nina side of neutral.
Moreover, van den Berg said “there is a large pool of cooler than normal sea surface temperatures just to the south of the Niño-areas and that it is possible that this pool may disturb the normal effect of El Niño or neutralise the effect”.
Although there are indications that El Niño has “probably reached its peak and can start to decay… we know from experience that there are phases of development that can strengthen it again”, report explains
“[The] bottom line indicates still a high level of uncertainty.”
A second scenario in terms of the current season forward, with a 30% probability according to van den Berg, is that the “El Niño reaction” won't be typical or can weaken rapidly, which could mean “good rainfall for the rest of the season”.
The report further noted that the southern parts of Namibia, which can be compared in climate outlook to the western parts of the Northern Cape, are facing poor prospects for rainfall.
A 11 January daily flood bulletin issued by the Hydrological Services Namibia noted that water levels on Namibia's northern borders, namely the Zambezi, Okavango and Kunene rivers, have been steadily rising due to “good rainfall received in their headwaters” over the previous days.
On the southern border, the Lower Orange River is experiencing very low water levels.
The water levels of major dams remain a concern overall, with the Swakoppoort Dam at 22.2% capacity, compared to 40.5% capacity one year ago.
The Von Bach Dam level, as per the 14 January dam bulletin, was at 51.3% capacity, compared to 52.1% capacity one week ago and 58.3% capacity the previous year.
The Hardap Dam is at 33.3% capacity currently, compared to 34.2% the previous year.
Water levels at the Naute Dam are currently at 64.6% capacity, compared to 65.5% a year ago.