Widespread above-average seasonal rains trigger severe floods and fatalities in several regions of East Africa

• Persistent well above-average seasonal rains continued across most parts of equatorial East Africa in April. The heavy rainfall led to widespread severe floods, causing fatalities, displacement, and crop and livestock losses in several regions, mostly in southern Somalia, western Rwanda, parts of Tanzania, Burundi, Kenya and Ethiopia.

• Apart from the reported severe floods, rainfall in March and April have largely been beneficial to cropping activities, pasture regeneration, and water replenishment across most of the pastoral and cropping areas worst-affected by the extended drought that lasted from late 2020 into early 2023. However, parts of northwestern Ethiopia, northeastern Somalia, and central and eastern Tanzania are still experiencing rainfall deficits.

• Available forecasts (GEFS and IRI/SubX) indicate an increased likelihood of continued heavy rains for the reminder of May, and an elevated risk of floods in southwestern and northern Ethiopia, northern Somalia, western Kenya extending into Uganda, Rwanda, and Burundi, together with parts of coastal East Africa. Meanwhile, below-average rainfall is forecast in western and some central areas of the region. Preliminary CHIRPS data for early May and GEFS forecasts through May 20 suggest an elevated likelihood of below-average May rainfall in parts of central Somalia, Kenya, and coastal Tanzania.

In March and April, the seasonal rains were characterized by intermittent moderate to localized very heavy rains, with cumulative totals ranging from 100 to 700 mm in most parts of Ethiopia, Somalia, and Kenya. Overall, rainfall during this period was mostly well above average (Figure 1), causing flash floods in several countries that resulted in fatalities, displacement of people, and property damage. Areas worst affected by flooding in April include Belet Weyne along the River Shabelle basin in Somalia and western Rwanda and neighboring southern Uganda and Kivu regions of DRC. Other areas that have been affected by widespread flooding include Bujumbura province in Burundi, parts of western and coastal Kenya, and Somaliland and Oromia regions of Ethiopia. Jubaland in Somalia also reported floods, but with relatively less severe impacts. On the other hand, parts of northwestern Ethiopia, northeastern Somalia, and central and eastern Tanzania experienced below-average rainfall performance, with less than 75 percent of average rainfall received in some areas. 

The exceptionally heavy rains in East Africa are largely attributable to the early passage of the Madden Julian Oscillation (MJO) as well as due to the presence of tropical cyclones in March owing to the warmer-than-normal sea surface temperatures (SST) over the neighboring Indian Ocean.

According to both satellite data and field observations, as of the end of April, there has been significant improvement in vegetation conditions, with better-than normal conditions now prevalent in vast areas of northeastern and central of Ethiopia, southern South Sudan, parts of northern Uganda extending into northeastern Kenya, and localized areas of Somalia (Figure 2). On the other hand, below-normal conditions persist over western Ethiopia, much of Sudan and central South Sudan, much of central, southern, and coastal areas of Somalia, and localized areas of Kenya and northeastern Tanzania. Recent rainfall is expected to drive further improvement in vegetation conditions – including due to pasture regeneration and crop development – in the coming weeks.

Surface water resources and rivers have also continued to be replenished by the ongoing moderate to heavy rains, bringing relief to pastoralist communities. However, the quality of the surface water resources is likely to remain poor for consumption due to siltation. Additionally, according to local health facilities, the incidence of water-borne diseases in both in urban and rural areas across the region are reported to have increased due to the recent flash floods.

According to available field information – and supported by the latest FEWS NET crop Water Requirement Satisfaction Index (WRSI) start-of-season simulation models – crop planting activities are expected to have started in all countries. Maize crops are generally reported to be in very good condition across most of the high- to medium-production zones in response to ongoing plentiful seasonal rains. If good rainfall persists throughout the remainder of the gu/long-rains seasons, then maize production prospects are generally favorable and better than what was earlier anticipated. However, beans and legumes planted in flood-prone areas are presently water-logged and have been partially damaged by the episodic very heavy rain, especially in Burundi, Rwanda, and parts of coastal regions.

The following is a country-by-country update on recent seasonal progress to date:

• In Somalia, according to WRSI simulation models for maize, the April to June gu seasonal rains started earlier than normal by around 10-20 days, with atypical rainfall received in March. Cumulative rainfall in March and April was above average across most parts of southern and northern Somalia, reaching over 200 percent of normal in several northern and southern areas. These heavy rains caused severe floods. Belet Weyne town was submerged, displacing over 200,000 people and damaging homes, property, and crops. The rest of country has experienced near average rainfall performance during this time. In southern Somalia, crops are generally in vegetative stages of growth and in near average to above-average conditions. Should rains continue throughout the season, crop production prospects are favourable. Rangeland resources have also improved significantly in both southern and northern Somalia, but remain below normal in central Somalia. Risk of flowing will persist in northern coastal areas and some southern areas as more moderate-to-heavy rains are forecast over the Ethiopian highlands and the Shabelle and Juba River basins in the next two weeks.
• In Ethiopia, the March to May seasonal rains have been characterised by well above average (more than 125 percent) rainfall amounts over most of the country as of the end of April, with localized areas of exceptionally heavy rains (exceeding 200 percent of normal). These abnormally heavy rains caused floods in Afder, Liban, and Fafan Zones of the Somali Region. However, the western regions of the country bordering Sudan are currently experiencing deepening rainfall deficits (with cumulative totals of less than 75 percent of normal), also contributing to drier-than-normal vegetation conditions. On the other hand, most pastoral regions of northern, southeastern, and southern Ethiopia have seen significant improvement in terms of pasture regeneration and water replenishment following the prolonged drought. A risk of flooding persists over southwestern areas of Ethiopia bordering South Sudan and along the central Rift Valley extending into Afar regions.
• In Kenya, the March to May seasonal rains are presently fully established. However, planting activities have been staggered following an early to timely onset of the rains in central, eastern, and coastal areas, and a delayed onset of the rains in some southern and western areas. The pastoral regions of northern Kenya also experienced an early onset of the rains. Most of the country has recorded well above-average rainfall amount. Flash floods were reported in Nairobi, Marsabit, and Moyale counties, including sections of the coastal strip of Kenya. Maize crops are now in vegetative stages of growth and are in good to very condition in response to the continued moderate to heavy rains. Should the rains continue normally, maize yield prospects are favorable across the country. Overall, rangeland resources have improved significantly across most of the country, except in areas that have been affected by recent floods and water-logging.
• In Sudan, the month of April was dry, as is typical, but temperatures were hotter-than-normal across the country. As such, vegetation conditions are currently drier-than-normal over its eastern and southern regions and are likely to deteriorate further as little-to-no rainfall is forecast in coming weeks, with the typical onset of seasonal rains expected in June.  
• In South Sudan, the ongoing first season rains in the bimodal zone commenced early. Cumulative rainfall totals have been average to above average across most of the country, and well above average rainfall in the southeastern regions and extending into northwestern Kenya. However, cumulative rainfall has been below average rainfall in localized areas of the northern regions bordering Sudan. In general, crops and vegetation have responded well to the ongoing seasonal rains. However, high White Nile River water levels have led to expansive areas inundated with flooding in the river basin and surrounding areas, especially in the flood-prone areas of Sobet, Akobo, and Pibor.

• In Uganda, rainfall performance in March and April (the start of the March to June first bimodal season) was generally average to above average, with the northeastern regions of Karamoja (whose rainy season is April to September) experiencing well above-average rainfall amounts. Crop and vegetation conditions are average to above average, though areas of below-average conditions persist, particularly in Karamoja. More heavy rains are forecast over Mt. Elgon regions bordering Kenya, with an increased risk of floods and landslides.
• In Rwanda and Burundi, Season B rains have been well above average, and excessively heavy over northern Burundi and western Rwanda. In Rwanda, there are reports of severe flooding causing fatalities and property loss in districts bordering the DRC. Beans and other legume crops have also been damaged due to the floods and associated waterlogging, with the extent of adverse impacts yet to be fully assessed. Overall, maize crop conditions are largely very good, with crops in vegetative stages. However, vegetation conditions are normal to below-normal due to the adverse impacts of anomalous rains and waterlogging. Floods risk remains elevated in both countries as heavy to very heavy rains are forecast into mid-May.
• In Yemen, the March to May seasonal rains have been characterized by well above average rainfall amounts over the western coastal and highland regions of the country. Widespread flooding has been reported, particularly impacting highland areas. According to the latest weekly forecasts and FAO reporting, risk of flooding will persist across much of the country, especially in Al Mahwit, Dhamar, Hajjah, Al Hudaydah, and Lahij extending into northern regions of Amran. Overall, vegetation conditions are better than normal across most of the western region of the country.

According to the IRI sub-seasonal (SubX) probability forecast for May 13-26, 2023, there is increased likelihood of below-average rainfall in much of Uganda, eastern South Sudan, western Ethiopia, and western Kenya (Figure 3). Meanwhile, rainfall during this period is forecast to be above average in parts of northern and southwestern Somalia, eastern Kenya, and northeastern Ethiopia extending into Eritrea. The rest of the region is expected to experience near average rainfall. The forecast rainfall is expected to have generally favorable impacts on cropping conditions and rangeland resources. However, there is a heightened risk of additional flooding in northern Ethiopia, northern Somalia, and parts of coastal East Africa due to forecast heavy rains and already saturated soils.

Rainfall to date in March and April plus available forecasts through May 20 suggest that most parts of East Africa are likely to continue to experience above-average cumulative rainfall totals as the season concludes in much of the region (Figure 4). However, of concern is the expectation for expanding rainfall deficits over northwestern Ethiopia and bordering areas of eastern Sudan. Rainfall deficits are also forecast to emerge in parts of northern South Sudan and south-central Somalia. This seasonal monitor report will continue to closely monitor the emerging rainfall deficits in these areas.

In the June to August period, available forecast models indicate an elevated likelihood of below-average rainfall in western and some central parts of the region (western Kenya, Uganda, southern South Sudan, and central and southwestern Ethiopia) and of above-normal rainfall in much of Sudan (Figure 5).  Forecast El Niño conditions have also been historically associated with dry conditions in the June to August period in many (though not all) seasons with active El Niño conditions. This is likely to affect the main kiremti rains in Sudan, Ethiopia, and neighboring South Sudan.

According to forecasts by the Australia Bureau of Meteorology issued in early May, there is an increased likelihood of rapid development of positive Indian Ocean Dipole (IOD) conditions beginning in June and lasting at least through September 2023. This on top of forecast El Niño conditions is likely to lead to above-average seasonal rainfall in the September 2023 to January 2024 period over much of the East African region. Expectations for above-average rainfall are supported by international ensemble forecasts.