Mixed bag for rain forecasts
Two experts share their opinion on what the coming rainy season holds.
08 October 2018 | Environment
Predictions for this year's rainy season in Namibia have had many references to El Niño and concern has increased for yet another year of low or no rainfall.
Speaking to Windhoek Express, Professor Peet Pienaar, a retired academic and meteorologist from South Africa, said this season may not be outstanding, but added that it will be better than last year.
“If you could draw a parabola of the five-year cycles of drought and wet seasons, you will see that we are at the second level of emerging from drought now,” he said.
Not concerned at all with the ENSO (El Niño and La Niña) phenomenon, Pienaar insists that with copious snowfalls, great sardine runs and a long, extended winter, the outlook for rain is better this year than last year and he added that he is “not worried” at all about the season.
When asked whether it will be good or bad this year, well-known South African meteorologist and follower of the ENSO phenomenon Professor Kobus Botha, said, “yes and no”.
“El Niño developed very strongly but has weakened. We are a little unsure as to what it will do. For Namibia, you can prepare for below-average rainfall at this stage. The phenomenon has strengthened and weakened almost every day so we really do not know other than it will be below average,” he said.
The American National Oceanic and Atmospheric Administration (NOAA) predicts a relatively neutral El Niño with a 50 to 55% chance up until November, increasing to 65-70% during our summer.
“Overall, the oceanic and atmospheric conditions reflected ENSO-neutral,” the administration said.
“The forecasters also favour El Niño formation during spring and are leaning toward the more conservative model guidance that indicates a weak El Niño event.”
For a fully-fledged El Niño event, the requirement is a 0.5°C increase to hold consistently for three months. Currently, the period of April/May/June is at -0.1°C and the two periods for May/June/July and June/July/August are only at 0.1°C.
At the height of our drought in the 2015/16 season, measurements went up to 2.6°C. The El Niño phenomenon, at the start of 2015, was at 0.6°C. It grew and grew, and eventually began to decline by April 2016, standing at 1.7°C
The next ENSO diagnostics discussion is scheduled for 11 October 2018.
That being said, Namibia's dams are not in good shape, in particular for the east and central areas of the country. The total volume of the central area dams stands at a meagre 26.9% with Von Bach holding 22% of that. Last year this time, the central dams held 43.3%. In the east, Otjivero is at 7% and for the region, total volume is at 5.1% compared to 12.8% last year.
In the south, Naute is at 77% while Hardap has 37.4%, bringing the regions' total to 45.7% compared to 60.8% last year.
Also, the City of Windhoek has already implemented its contingency measures and other towns, including Okahandja and Gobabis, reliant on dams that are mostly close to empty, have been planning for borehole extraction.
Whichever of the predictions pan out, rainfall will most certainly be capricious. Let us hope that it rains in the catchment areas of our major dams, in particular, those of the central areas.
What to believe
According to Pienaar, the folklore surrounding whether or not it will rain, is mostly correct and based on scientific principles.
• The elders say when the snakes come out, the rain will come. This is correct as snakes respond to low pressure systems and are active during such a time. Rainfall can only come when there is a low-pressure system.
• Finches build their nests high or low. This is also correct. The higher the nests, the greater the chance of good rainfall.
• It never rains on full moon. This is correct. During full moon, the sea has higher swells due to the gravitational forces. This causes a mixing of the different layers of water and increases evaporation. It rains three or so days after full moon.
• Rain is coming when insects abound around lights. This is correct, as they too respond to low-pressure systems.
• If you own a tortoise, watch its behaviour. If it is constantly looking up for an extended period of time, rain will fall around three days later.