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Delayed onset and below-average April rainfall likely for much of East Africa

  • Seasonal Monitor
  • East Africa
  • March 29, 2019
Delayed onset and below-average April rainfall likely for much of East Africa

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  • Key Messages
  • SEASONAL PROGRESS
  • FORECAST
  • Partner
    USGS
    Key Messages
    • March rainfall performance was poor across much of East Africa, signaling both a delayed and uneven onset of the March – May seasonal rains. This was largely attributed to the unexpected presence of a severe tropical cyclone Idai last week over Mozambique and neighboring countries, which disrupted East Africa’s rainfall system.

    • Prolonged dry and hotter-than-normal conditions persist over pastoral and marginal agricultural zones over the eastern Horn and parts of northern Uganda, a continuation of drought conditions as a result of below-average October – December seasonal rains.

    • The rainfall outlook for the remainder of March into April remains unfavorable and erratic, but with a short-term increase in rainfall this week. However, the rains are forecast to give way to dry conditions in early April. This is a critical crop planting and germination period in East Africa, and failure of the rains is often associated with reduced to failed crop yields in marginal cropping areas.


    SEASONAL PROGRESS

    March rainfall performance was largely below average across East Africa, especially in northern Tanzania, Burundi, Rwanda, Uganda, Kenya, and parts of the Belg-dependent cropping areas of Ethiopia. Cumulative rainfall from March 1st to 20th resulted in significant deficits, ranging from -50 mm to -100 mm (Figure 1). However, there were areas of average to above-average rainfall amounts over the Lake Victoria basin, southwestern Tanzania, and parts of southwestern and central Ethiopia. Additionally, uneven distribution of rainfall in the western sector permitted areas of early rainfall onset in parts of Rwanda, Burundi, and southern and central Uganda, even as other areas experienced a timely to delayed onset.

    Overall, the seasonal rains remain generally disrupted and they have yet to be fully established in late March, a critical planting period in key agricultural production zones of Kenya, Uganda, Rwanda, Burundi and Belg-cropping areas of Ethiopia. This is largely attributable to the recent development and adverse impacts of tropical cyclone Idai over Mozambique, Malawi, and Zimbabwe. Its presence and abnormal track inland last week disorganized East Africa’s rainfall system by concentrating rainfall over these southern African countries and in parts of southwestern Tanzania. Prolonged sunny and hotter-than-normal conditions continued across East Africa and exacerbated current drought conditions in pastoral and marginal agricultural areas of Uganda, Kenya, Somalia, and eastern Ethiopia.

    The impact of poor rainfall performance is evidenced in the latest eMODIS/Normalized Difference Vegetation Index (NDVI) (Figure 2), which depicts vast areas of significantly drier-than-normal conditions over much of the eastern Horn, as well as in parts of southern, central, and western Kenya. Similar conditions can be seen in northeastern regions of Tanzania, the Rift Valley, and southeastern regions of Ethiopia. In contrast, much needed improvements in vegetation condition occurred in South Sudan, western and northwestern Ethiopia, and localized areas of northern Kenya due to favorable early season rains in February.

    Short-term relief from forecast erratic rainfall in April is currently not anticipated to alleviate prevailing dry conditions. Should dry and exceptionally hot conditions persist, rangeland resources are anticipated to deteriorate further in some of the worst drought-affected ASAL counties of Kenya, Somalia, and eastern Ethiopia.

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

    • In Somalia, March has remained typically dry, but exceptional hotter-than-normal. This has led to rapid deterioration in surface water and pasture conditions across the country. These prolonged dry conditions are forecast to continue into early April, which would lead to below-average crop and pasture performance. April is the most critical month for the rainfed sorghum growing zones of southern Somalia. Forecast delayed onset and below-average seasonal rains raises the likelihood of two consecutive poor crop seasons, following the 2018 Deyr. However, the rainfall forecast is likely sufficient to at least partially replenish rangeland resources.
    • In Ethiopia, continued slightly above-average to average February-March rainfall over parts of the Belg-dependent regions of SNNP, Oromia, and parts of Afar and northeastern Somali regions have resulted in favorable cropping and rangeland conditions. As depicted by eMODIS/NDVI anomalies, vegetation conditions have gradually improved in these regions. However, areas of drier-than-normal vegetation conditions have persisted since February along the Rift Valley zones of Ethiopia, from its southwestern into its northeastern sector. In the next two weeks, more widespread moderate to locally heavy rains are forecast over some of the Belg cropping zones and southern pastoral zones, which would improve rangeland resources. However, the eastern Somali region of the country is expected to remain dry and hot during this period.
    • In Kenya, unevenly distributed but moderate to heavy rains are forecast for the next two weeks in unimodal cropping areas of the western and northern Rift Valley. This could trigger widespread planting across these key maize production zones, but the delayed onset and insufficient rainfall amounts would lead to a false start of season. In much of the marginal agricultural areas in the eastern and southeastern lowlands, this is a critical maize planting period and the short-term forecast indicates increased likelihood for a delayed onset with erratic and below-average amounts in April. The most-likely scenario is indicative of a consecutive below-average cropping season in these areas, despite a forecast of moderate to locally heavy rains in the coming weeks, which would alleviate current drought conditions. Nevertheless, Turkana, Marsabit, West Pokot and Samburu are unlikely to receive significant rains during this period and drought conditions are likely to worsen.
    • In Sudan, March remained typically dry and hot, despite generally favorable vegetation conditions across the country. Dry and hotter-than-normal conditions are forecast across the country for coming months with little or no rains forecast until the onset of its main June – September seasonal rains.
    • In South Sudan, better-than-average vegetation conditions persisted across of the country, similar to Sudan. No significant rains are forecast in most of the country for the next two weeks, except in the southeast. Gradual improvement in rangeland resources is expected to continue in these areas into April.
    • In Uganda, early planted crops are experiencing high moisture-stress in the south, following prolonged dry spells in March. Suppressed early March rains greatly disrupted seasonal agricultural activities, particularly planting, which has now been delayed for more than three weeks for most farmers. Consensus national and regional forecasts are indicative of uneven and below-average rainfall amounts in April for much of the country, despite an anticipated short-term increase in rainfall over the next one-to-two weeks. Most parts of the country are yet to plant and no sufficient crop planting rainfall amounts are forecast during this period. Overall, cumulative March – May seasonal rainfall is anticipated to be near-average. To date, Karamoja region has not received rainfall, but it is not yet late, though atypically hot conditions are causing rapid deterioration in pasture and water availability.
    • In Rwanda and Burundi, season B rainfall performance was generally below average in March, despite the early onset of the rains in February. The short-term rainfall outlook indicates the establishment of the seasonal rains in April, with fairly favorable cropping conditions across both countries.
    • In Tanzania, 2018/19 Msimu maize crops are currently in the reproductive to maturity stages, with average to slightly above-average yield prospects expected, following good seasonal rainfall performance. Meanwhile, northeastern bimodal regions have continued to experience a delayed onset with below-average and erratic rainfall performance.
    • In Yemen, March was generally sunny and dry. There is increased likelihood for light to moderate rains in the coming weeks over the western highland and coastal areas of Yemen. The rest of the country is expected to remain typically sunny and dry.

    FORECAST

    The short-term rainfall outlook through April 2nd shows an increased likelihood of widespread, moderate to locally heavy seasonal rains over Tanzania, Rwanda, Burundi, southern and central Uganda, and much of Belg cropping zones and parts of southern Ethiopia, as well as northeastern, central, and eastern Kenya (Figure 3). A few regions of southern Somalia bordering northeastern Kenya are also likely to receive moderate rains. However, these rains are forecast to be episodic and short-lived, subsiding into dry spells in early April for much of eastern Horn, including central and northern Uganda.

    Lack of an organized rainfall system in the next two weeks of April is likely to be unfavorable and delay timely crop planting over northeastern Tanzania, southeastern Kenya, and much of southern Somalia. These are marginal cropping zones, with typically low seasonal rainfall amounts that rely heavily on late March and April rains. Failure in timely onset and sufficient rainfall amounts are expected to result in consecutive below-average cropping seasons. This is attributed to the continued presence of warmer-than-normal sea surface temperatures in the southern Indian Ocean, which remain conducive for the generation and strengthening of tropical storms or cyclones that can disrupt rainfall in East Africa and result in  drier­-than-average conditions.

    The performance of the next two to three weeks of rainfall is absolutely critical over the eastern Horn. FEWS NET and its network partners will continue to closely monitor and provide updates about the evolving climatic situation.

    Figures

    Figure 1

    Source: FEWS NET/USGS

    Figure 2

    Source: FEWS NET/USGS

    Figure 3

    Source: FEWS NET/USGS

    FEWS NET’s Seasonal Monitor reports are produced for Central America and the Caribbean, West Africa, East Africa, Central Asia, and Somalia every 10-to-30 days during the region’s respective rainy season(s). Seasonal Monitors report updates on weather events (e.g., rainfall patterns) and associated impacts on ground conditions (e.g., cropping conditions, pasture and water availability), as well as the short-term rainfall forecast. Find more remote sensing information here.

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