African SWIFT report on flooding and heavy rainfall in Kenya

Report by SWIFT Research Team from Kenya Meteorological Department (KMD)

Emmah Mwangi, John Mungai and Benard Chanzu report:

During the March-May (MAM) 2018 season most parts of Kenya have received enhanced rainfall, which was characterized by intense storms.  As at 26th April, 2018 much of the country had already received rainfall that was over 125% of the MAM Long Term Mean (LTM) as shown in Figure 1.

Figure 1: Rainfall total up to 26th April compared to the MAM long term Means

The heavy rainfall has caused flooding, landslides, loss of property and life in some parts of the country. Much of the flooding has occurred in urban and low lying areas and has been as a result of two factors, namely:  the intense rainfall events over most parts of the country and accumulated heavy and continuous rainfall in the upper catchment areas that are sources of some of the rivers that broke their banks.

The heavy rainfall can be attributed to three factors: firstly, at the beginning of the season (Early March) heavy rainfall over much of the country was caused by the presence of two tropical cyclones in the Indian Ocean; Dumazile and Eliakim. The Cyclones caused heavy rainfall by pulling in moisture from the Congo basin and creating a pressure gradient that pulled the North-South arm of the rainfall generating Inter Tropical Convergence Zone eastwards.

Secondly, for most of the season the Madden Jullian Oscillation (MJO) was conducive. The MJO is a band of convective clouds and rain moving west to east. The circulation occurs in various phases that can be either conducive or unfavorable for rainfall generation over Kenya. This time around, the circulation has been persistently been in the phases that are conducive for rainfall enhancement over Kenya and hence heavy rains that have pounded the country within the season. Thirdly, the warm Sea Surface Temperatures over the Western Indian Ocean sustained the convergence belt over the region.

Frequent flooding and droughts are part of the climatic variability in Kenya. However, these events have become more frequent and intense as a result of climate change which is being experienced globally. These events are projected to be more frequent and intense in future hence, there is need to institute effective adaptation and contingency plans amongst the vulnerable communities to ensure they are not severely impacted. There should be timely use of Early Warning information to minimize impacts associated with these extreme climate events. Awareness creation amongst the vulnerable communities on what needs to be done in case of the occurrence of these events need to be enhanced.

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