How heavy will the coming rains be? The weatherman says the answer is not in El Niño. It is in the ocean right next to Kenya.
Jemima Gacheru, a principal meteorologist at the Kenya Meteorological Service Authority (KMSA), explained that although the world is already under a strong El Niño, this phenomenon alone cannot tell how much rain will fall in Kenya in October-December.
The bigger question for the country is what happens in the Indian Ocean through a climate pattern known as the Indian Ocean Dipole (IOD).
“So this is just to demystify that notion that El Niño is always equal to rainfall. That is not always the case,” Gacheru said at a webinar hosted by the KMSA.
She said Kenya has had strong El Niño seasons with very little rain, because the Indian Ocean near the Kenyan coast did not warm up as expected.
The IOD measures the difference in sea temperatures between the western Indian Ocean, near East Africa, and the eastern Indian Ocean, near Indonesia. When the waters near the East African coast become warmer than normal, this is called a positive IOD, and it supports heavier rainfall in East Africa.
She said the IOD is currently a weak positive, and not as strong as 1997, but that could change.
“It is currently positive at 0.7 degrees Celsius, and it is expected that as we go into the October, November, December season, it will rise to a maximum value of 1.0 degrees, particularly in October,” Gacheru said.
However, the Australian Bureau of Meteorology reports a weekly IOD index of +0.65°C for the week ending September 13, classifying it as neutral, noting that one observation above +0.4°C does not establish a positive IOD event.
Gacheru said the strength of the IOD could determine if Kenya has extremely heavy rain or a more mixed rainfall pattern.
She pointed to 1997 as an example. That year had a strong El Niño and a strong positive IOD (1.4 degrees Celsius in November 1997), and Kenya recorded heavy rainfall across most of the country.
But 2015 was different. That year also had a strong El Niño, but the IOD was only about 0.5 degrees.
Kenya therefore experienced a mixed rainfall pattern, with some areas receiving above-normal rainfall, others near-normal rainfall and some areas below normal.
This means the coming season is unlikely to repeat the 1997 experience, because the strength and behaviour of the Indian Ocean must also be considered.
Nevertheless, Gacheru said the current forecast expects most counties to receive above-normal rainfall.
She said the forecast should not be read as meaning that every place will receive the same amount of rain.
“Most areas are expected to have fair to good distribution, meaning the dry spells will not be as many. But for areas such as Turkana and Samburu, rainfall is likely to begin around the third or fourth week of October and may end in the first week of December and the distribution there may not be very good,” she said.
Ruth Njeri, a senior agricultural officer in the State Department for Agriculture’s Climate Change Unit, said farmers could use the expected moisture to improve food production.
“This will give us maximum soil moisture utilisation, which our farmers are encouraged to take advantage of. We will be able to store water for long-term aquifer recharge and rebuild household food stocks,” she said.
Njeri warned that too much water could also damage crops through floods, pests, diseases and poor storage.
“We are also looking at the risks, including flash floods, which may destroy crops and post-harvest spoilage due to mould and flood toxins. Crop and pest diseases may also increase because moisture and prolonged humidity create favourable conditions for pests and weeds,” she said.
Livestock farmers also stand to benefit if the rains are well distributed.
The Environment ministry urged Kenyans not to treat the forecast as a cause for panic.
Dr Sally Kimosop, Environment Secretary in the Ministry of Environment, Climate Change and Forestry, said the purpose of the warning was to help people act before the rains arrive.
“El Niño is no longer a distant phenomenon in the Pacific Ocean. It is a phenomenon that directly affects our food, our health, our livestock and our economy,” Kimosop said.
“Late action is expensive and therefore early action saves lives and saves resources. El Niño is a climate phenomenon, but a disaster is not inevitable,” she said.
The National Disaster Operations Centre is already preparing for possible flooding and other impacts. It has identified the Tana and Victoria basins and landslide-prone areas for anticipatory action, including flood monitoring and early warnings.
The lesson from previous years is therefore simple. Farmers and communities should not wait for the rains to judge whether the forecast was right.
