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Slow onset of March-May rains with increasing early season rainfall deficits

  • Seasonal Monitor
  • East Africa
  • March 15, 2021
Slow onset of March-May rains with increasing early season rainfall deficits

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  • Key Messages
  • Key Messages
    • The March-May seasonal rains are gradually being established over Rwanda, Burundi, Uganda, and southwestern Ethiopia. However, these seasonal rains are yet to be fully established across the region's equatorial sector, increasing concerns for delayed onset and early season cumulative rainfall deficits during the past month.

    • Rangeland resources have continued to rapidly deteriorate across the pastoral and marginal agricultural areas of the eastern Horn, following the poor 2020 October–December rains and prevailing hotter-than-normal land surface temperatures, in particular eastern Kenya, southern Somalia, southern and western Ethiopia, southern South Sudan, and northwestern Uganda.

    • In February, immature desert locust swarms were generally located across East Africa's central rift-valley regions, central and northeastern Ethiopia, northern Somalia, and eastern Kenya. In late February, rainfall is likely to allow swarms to mature rapidly in northern Kenya and southern Ethiopia, with hatching in late March or April around crop planting. However, on-going effective control measures and below-average rainfall is expected to limit breeding.

    • There is an increased likelihood for delayed onset of the seasonal rains in March with increasing cumulative rainfall deficits, especially over vast areas of the eastern Horn, central and northern Uganda, and belg-receiving areas of Ethiopia.


    The onset of the seasonal rains in Burundi and Rwanda, southern and parts of central Uganda, and localized areas of southwestern belg cropping areas in Ethiopia's SNNPR areas were largely early to timely from mid to late-February. Since mid-February, these regions have recorded above-average to average rainfall amounts, while eastern DRC recorded significant cumulative seasonal rainfall deficits (Figure 1). Early seasonal rainfall deficits are also evident over most belg areas of Ethiopia, parts of central and northern Uganda, and southern Kenya.

    The seasonal rains are yet to be fully established across the rest of the region dependent on the March-May Gu/long-rains.  Typically, these seasonal rains are often established between late March and early April across equatorial East Africa. Meanwhile, prolonged dry and hotter-than-normal conditions continue to prevail across the eastern Horn but punctuated by unseasonal localized moderate rains in southern and central Kenya, mostly attributed to disruptive tropical cyclones/depressions over the past months.

    The poor performance of the 2020 deyr/short rains, coupled with the on-going prolonged dry season, has resulted in the deterioration of vegetation conditions over vast areas of the eastern and northern sectors (Figure 2).  The worst-affected areas are currently in Oromia and parts of western Ethiopia, southern Somalia, eastern and northeastern Kenya, and northeastern Uganda, where there are concerns for water availability for human and livestock use. Meanwhile, much of Yemen, northern Sudan, and Somalia presently are experiencing greener-than-average vegetation (Figure 2).  The rest of the region has near-average vegetation and surface water conditions, but an increasing area is expected to experience rapidly deteriorating surface water resources under current climatic conditions.

    Meanwhile, much of the early planted crop in the region's bi-modal areas are at emergence to early vegetative stages and in favorable condition with sufficient soil moisture, confirmed by both field assessments and FEWS NET crop simulation models. Field reports also indicate delayed planting in Ethiopia's belg cropping regions and southwestern and central rift regions of Kenya and central Uganda. The seasonal rainfall performance in the coming weeks will be critical for the performance of the agricultural season.

    Desert locusts remain a risk over much of East Africa during this crop-growing period. According to the latest field reports from FAO and national partners, there has been effective control of the large immature swarms that had migrated southwards from northern Somalia and Ethiopia into rift valley regions of southern Ethiopia and  Kenya. The start of the rains will likely create favorable environmental conditions for desert locust laying and hatching. Sustained close monitoring and coordinated control of these pests are needed to mitigate possible adverse impacts on crops and vegetation.

    Confirmed COVID-19 pandemic resurgence in Ethiopia, Kenya, and Tanzania is likely to continue affecting East Africa's socio-economic sectors. There is on-going COVID-19 vaccination activity across the region, but local population access to vaccines will remain a constraint due to limited supply.

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

    • In Somalia, current rangeland resources have significantly deteriorated across most of southern Somalia, following a largely poor deyr rainfall season, coupled with a prevailing hotter-than-normal dry season, causing the depletion of surface water pans. If the rains are delayed and poor during the upcoming Gu season, livestock body conditions and production are expected to be negatively affected.  Meanwhile, much of central and northern Somalia is currently under relatively better rangeland conditions following atypical rainfall (tropical cyclones/depressions) over the past months, particularly in northern and central coastal areas. April and May are critical months for Somalia and require close monitoring of the evolving climatic situation. If the Gu is below-average, then agricultural production and food availability will be adversely affected.
    • In Ethiopia, there are increasing concerns for the significantly delayed onset of the belg season for much of Ethiopia, particularly in the northern and central belg-receiving areas. In the belg-receiving areas of SNNPR, which had an earlier-than-normal start of the season, crops are in a favorable condition and the emergence to early vegetative crop stages. Much of Ethiopia shows mixed vegetation conditions, with significantly drier-than-normal conditions over the southern and southeastern regions. Meanwhile, the northern and parts of the central regions have remained greener-than-normal, having benefited from unseasonal localized moderate rains in February from the movement of the north-south (meridional) arm of the ITCZ.  If the current climatic forecast prevails, there are serious concerns for a largely poor 2021 gu/genna agricultural production.
    •  In Kenya, the failed 2020 short-rains season and increased likelihood for another consecutive poor 2021 March-May rainy season are likely to adversely affect the vulnerable pastoral and marginal agricultural communities in northern and eastern Kenya. Current and forecast climatic conditions are indicative of below-average to crop failure scenarios. April is typically the peak month for the long rains season across eastern and northeastern Kenya, and there is a heightened need for close monitoring of the season. Meanwhile, the western Rift Valley and parts of central Kenya are expected to have average to above-average rainfall and a good agricultural production season. Along with on-going concerns for delayed onset and erratic establishment of the seasonal rains, agricultural production and food availability across the country are likely to be impacted by crop loss from desert locusts and socio-economic impacts of COVID-19 control measures on local populations.
    • In Sudan, the dry season is expected to continue until the onset of seasonal rains in June.  No rains are forecast in the coming weeks. Current environmental conditions are varied, but with generally better-than-normal to normal vegetation coupled with near-normal to hotter-than-normal land surface temperatures. However, in western Sudan, drier-than-normal vegetation conditions remain following the recent crop harvest and in localized areas with below-average June-September 2020 seasonal rains and a prolonged dry season. However, in the central and northern regions, vegetation conditions are likely to rapidly deteriorate in the coming months, driven by the forecast hotter-than-normal dry season. Vegetation conditions in the south are likely gradually decline due to forecast near-average surface temperatures.
    • In South Sudan, much of the country has remained normally dry and hot, with occasional rains over the southwestern and eastern border regions with DRC and Ethiopia. However, seasonal rains over the southern border areas have largely been below average, an extension of what is being observed in eastern DRC, parts of northwestern Uganda, and southwestern Ethiopia. Overall, vegetation conditions across the northern and the Nile valley regions have remained exceptionally better-than-average, with localized drier-than-average conditions in parts of its southern sector. A near-typical decline in vegetation conditions is expected due to the forecast average land surface temperatures during this dry season over the central and northern regions. Light to moderate rains is forecast in this sector in the coming weeks with the tropical rainfall system's gradual northward shift (ITCZ).
    • In Uganda, the southern and parts of the central districts experienced an earlier-than-normal onset of the seasonal rains in mid-to late-February. This is likely to have triggered early planting and favorable cropping conditions. However, in the central and northwestern sectors, the seasonal rains are yet to be established, and there is evidence of early season rainfall deficits. There continue to be rainfall deficits and drier-than-normal vegetation conditions in the northwestern and parts of western Uganda bordering DRC. Desert locusts are currently not a threat; however, changes in seasonal easterly wind regimes could see immature swarms entering from Kenya. Overall, favorable cropping and pastoral conditions are likely across the country despite the current erratic rainfall onset and mixed performance.
    • In Rwanda and Burundi, Season B rains were established in February with the most timely planted crops in vegetative stages with sufficient soil moisture. Vegetation and cropping conditions are likely to significantly improve with moderate to heavy rains forecast in the coming weeks. However, COVID-19 related restrictions may limit local transportation and access to agricultural inputs and markets.
    • In Yemen, uncharacteristic greener-than-normal conditions have remained since February, with occasional unseasonal rains due to the presence of tropical cyclones/depressions in the vicinity. Land surface temperatures have also remained cooler-than-normal over the western and southern coastal regions, including the central highlands. However, vegetation conditions are expected to worsen, driven by the forecast below-average first-season rains between March and May. There are little or no desert locusts, but typical seasonal wind directions pose a risk for invasion from neighboring countries.



    According to the rainfall outlook for March 15 to 31, there is an increased likelihood for delayed onset and continued increase in cumulative seasonal rainfall deficits across much of the long-rains-dependent areas of equatorial East Africa. Much of East Africa is likely to remain abnormally dry and hotter-than-normal, except for Rwanda, Burundi, eastern DRC, southern Uganda, and highlands areas of Kenya and southwestern Ethiopia (Figure 3).  There is an increased likelihood for delayed onset and crop planting across much of the region's eastern sector, including northeastern, central, and northern belg-cropping areas. There are also concerns of long-dry spells for the region's western sector, especially in areas where early planting has already occurred.

    Poor rainfall through March is likely to drive significant early season rainfall deficits of 25 mm to 100 mm in southern, parts of western and southeastern coastal regions of Kenya and northern Uganda (Figure 4). However, there are also areas of above-average cumulative rainfall in Rwanda, Burundi, southern Uganda, and southwestern Kenya, which have recorded an early to the timely onset of the on-going seasonal rains. The rest of the region is expected to have near-normal conditions through March, particularly Somalia, eastern Ethiopia, and Yemen. Typically, the rainfall onset is in April, which is expected to be erratic and delayed.

    The lingering adverse effects of the late 2020 to mid-2021 La-Nina event, coupled with continued warm west Pacific Ocean SST gradients, are likely to continue driving poor eastern Horn seasonal rains, similar to what occurred during the 2020 deyr/short-rains seasons in the region.  


    Figure 1

    Figure 1.

    Source: UC Santa Barabara Climate Hazards Center

    Figure 2

    Figure 2.

    Source: FEWS NET

    Figure 3

    Figure 3.

    Source: NOAA/CPC

    Figure 4

    Figure 4.

    Source: UC Santa Barabara Climate Hazards Center

    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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