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Above-average seasonal rains significantly improve rangeland, water, and cropping conditions in the region

  • Seasonal Monitor
  • East Africa
  • May 31, 2023
Above-average seasonal rains significantly improve rangeland, water, and cropping conditions in the region

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  • Key Messages
  • Seasonal Progress
  • Forecast
  • Partner
    USGS
    Key Messages
    • The March to May seasonal rainfall performance was well above average, making it one of the wettest on record, particularly in parts of Ethiopia and Kenya. However, localized below-average rainfall was recorded in central Somalia, southern Kenya, and parts of eastern and northern Uganda into southern South Sudan, areas that rely on the long-rain seasons for crop cultivation.

    • While widespread flooding in April and May resulted in crop damage and displacement, the above-average March to May seasonal rains have generally culminated in significantly improved vegetation, surface water, and cropping conditions across the region and are likely to result in favorable cereal and legume yield prospects, even in the vulnerable marginal agricultural areas in the eastern Horn, providing considerable relief following the severe 2020-2023 drought.

    • The rainfall forecast for June is marked by the gradual but uneven northward progression of the tropical rainfall system (ITCZ) into Ethiopia, Sudan, and South Sudan. The March to May rains are expected to subside in June into dry conditions over the eastern region, except for moderate to heavy rains over the coastal strip of Kenya and northern and western East Africa.


    Seasonal Progress

    The March to May seasonal rainfall performance was largely above average across most of East Africa, with parts of southern Yemen, Djibouti, northwestern Somalia, northern Kenya, and along the Rift Valley and northeastern regions of Ethiopia experiencing one of the wettest seasons on record over the last 40 years, ranging from 150 to 300 percent of average (Figure 1). In April and May, heavy rainfall continued to cause widespread flooding, resulting in human and livestock fatalities, crop and property damage, and population displacement in the worst-affected areas. However, in late May, rains largely subsided, decreasing regional flood risk in most areas. Meanwhile, below-average rainfall and atypical dryness were recorded in northern and eastern bimodal Uganda and localized pockets of central Somalia between March and May.

    Figure 1

    CHIRPS cumulative rainfall, March 01– May 31, 2023 percent of 1991-2020 average
    Map of East Africa showing CHIRPS cumulative rainfall, March 01– May 31, 2023 percent of 1991-2020 average

    Source: UC Santa Barbara Climate Hazards Center

    Overall, the above-average March to May rainfall significantly improved rangeland resources, including both pasture and surface water, resulting in favorable cropping conditions and much-needed relief from the devastating 2020-2023 drought. Preliminary CHIRPS data for the month of May and GEFS forecasts through June 15 (Figure 2) indicate no significant changes in rainfall performance trends in early June. With the seasonal shift of the tropical rainfall system northwards and the gradual establishment of the June to September rainfall season, some early rainfall deficits in the western Ethiopian highlands into neighboring regions of eastern Sudan and South Sudan were apparent as of mid-June. Meanwhile, the western Darfur regions of Sudan are forecasted to receive above-average rainfall during this period, with an elevated risk of perennial floods.

    Figure 2

    Cumulative rainfall forecast for March 01 – June 15, 2023, expressed as percent of the 1991-2020 average; based on CHIRPS final data for March 01- April 30, CHIRPS prelim data for May 01 - 31, and unbiased GEFS forecast for June 01 - 15, 2023
    Map of East Africa showing Cumulative rainfall forecast for March 01 – June 15, 2023, expressed as percent of the 1991-2020 average; based on CHIRPS final data for March 01- April 30, CHIRPS prelim data for May 01 - 31, and unbiased GEFS forecast for June 01 - 15, 2023

    Source: UC Santa Barbara Climate Hazards Center

    According to the latest satellite-based vegetation data and field observations, as of the end of May 2023, most pastoral, agro-pastoral, and agricultural livelihoods zones are showing positive vegetation anomalies due to the above-average seasonal rainfall in the region (Figure 3). Meanwhile, drier-than-normal conditions are observed in the western Ethiopia/eastern Sudan border region, parts of northern South Sudan, and in central Somalia.

    Figure 3

    evMODIS/eVIIRS Normalized Difference Vegetation Index (NDVI), percent of the 2003-2022 median, May 21- 31, 2023
    Map of East Africa showing evMODIS/eVIIRS Normalized Difference Vegetation Index (NDVI), percent of the 2003-2022 median, May 21- 31, 2023

    Source: USGS/FEWS NET

    In May, surface water resources and rivers continue to be replenished at normal to above-average levels, as indicated by FEWS NET Water-Monitoring products and partner reports in Somalia, Kenya, and Ethiopia. The risk of water-borne diseases and malaria remains elevated in regions of extreme rainfall and is likely to reduce with the forecasted cessation of March to May seasonal rains in East Africa.

    FEWS NET crop simulation models (WRSI) for mid-season cropping conditions to end-of-season maize production prospects indicate largely average yields in Kenya, Burundi, and southern Uganda, key cereal-producing regions, if the rains continue normally through the end of the season. However, emerging concerns for possible mediocre to poor yields over parts of eastern Rwanda, eastern Kenya, northern Uganda, and southern Somalia marginal agricultural zones due to the expected cessation of the seasonal rains amid critical high-water demand for the maize crop’s current reproductive stage.

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

    • In Somalia, the Gu-seasonal rainfall performance is largely average, but with regions of well above-average amounts over southwestern districts of Juba region neighboring Kenya and northwestern Somalia. Flood risks remain imminent over the northwestern regions of Somalia bordering Djibouti. Meanwhile, parts of central Somalia into parts of Shabelle experienced below-average performance with drier-than-normal vegetation, while much of the country is currently under greener-than-normal to normal vegetation conditions as evidenced in the latest eVIIRS/NDVI anomaly images. However, the cropping conditions are generally favorable in the southernmost parts of the cropping into parts of Bay/Bakool region. The Bay sorghum growing areas show good to mediocre crop conditions with indications of average to reduced yield prospects at the end of the season.
    • In Ethiopia, belg/diraac/sugum rainfall was exceptionally above average for much of the northeastern, Rift-Valley and into parts of the southwestern regions of Ethiopia. The rest of the country had near-average performance but with increasing early seasonal rainfall deficits over the western highlands that rely more on the June to September kiremt rainfall. Flooding subsided in May, but the forecasted heavy rains over central and western highlands heighten the risk of floods as the kiremt season gradually gets fully established. However, the highly likely development of a moderately strong El-Nino event in the coming months is likely to suppress the overall performance of kiremt/karma/karan rains across the country, with particular concern for the northeastern parts of the country. By contrast,  most forecasts indicate average cumulative seasonal rainfall performance over the western highlands. The rest of eastern regions of Ethiopia are likely to remain typically dry and hotter-than-normal during this period into September.
    • In Kenya, March–May seasonal rains were characterized by well above average performance over the northern, eastern, and coastal counties of Kenya. Meanwhile, the high and medium maize production regions of western and rift valley counties observed mostly average rainfall amounts with favorable maize yield prospects if the rains continue normally into September. However, these rains are expected to have a timely cessation in early June over much of the eastern marginal cropping zones at critical the maize reproductive stage, which could contribute to significantly reduced yield prospects. Along the coastal marginal strip, while conditions were wetter than normal as of May, poor temporal distribution has affected yields and is likely to result in a below-average harvest.
    • Sudan, the June–September seasonal rains are forecast to have a timely onset with above-average rainfall amounts in June particularly over central and western parts of the country. Flood risk remains elevated over western Darfur. On the other hand, the early season mid-May into June rains over eastern Sudan have generally been below average with concerns for localized below-average cumulative performance due to the anticipated suppressed seasonal rains likely to be influenced by the forecast development of El Nino in sync with positive IOD during the July – September seasonal rains. Presently, vegetation conditions are generally near-average, but with drier-than-normal conditions over the east and southeast due to the ongoing seasonal rainfall deficits. Agricultural activities typically start when the rains get established this month into July, but the extent of cultivation is expected to be significantly below average due to the conflict.
    • In South Sudan, vegetation conditions are currently greener than normal over eastern Equatoria State and along the Nile river basin, mostly due to the above-average March–May seasonal rains and high river levels for past months. Drier-than-normal conditions persist over the northern and central States, with near-average conditions over the western sector. June–September seasonal rains are yet to be established in bi-modal regions, however, the June weekly to monthly forecasts are indicative of a timely and favorable onset of the rains but are expected to be generally below average in amounts with the imminent development of El Nino conditions at the peak of rains in July through September.
    • In Uganda, March-May seasonal rains in southern and western bimodal regions have largely been average, with below-average and spatially and temporally erratic rainfall in parts of eastern and northern Uganda. Rangeland resources remain favorable across the country; although slightly below average in Karamoja. The rainfall outlook and negative impact of the erratic rainfall in northern and eastern unimodal Uganda are driving increasing concerns about potentially below-average maize yields and production prospects by the end of the season. Maize is currently at varied stages of development ranging from reproductive stages in southern and Lake Victoria regions, early vegetative stage in northern districts, and late vegetative phenological stage in western, central, and parts of eastern Uganda.
    • In Rwanda and Burundi, vegetation conditions in both countries are generally average, with slight positive vegetation anomalies following the average Season B rainfall in Rwanda and above-average Season B rainfall over much of Burundi and western Rwanda. Southern Burundi recorded one of the wettest seasons in the last 40 years and cropping conditions are mixed with average maize production prospects for Burundi and significantly reduced yields projected in Rwanda due to the delayed onset and uneven distribution of rainfall and flooding at the peak of the seasonal rains. In May, the seasonal rains have shifted northwards, with moderate rains forecast for eastern Rwanda and no remaining flood risks.
    • In Yemen, the March–May seasonal rains were wettest in CHIRPS 40-year climatology across the country, resulting in exceptional greener-than-normal conditions, especially over the western coastal and highlands regions. Currently, these rains have significantly subsided apart from the forecast light to moderate rains over the southwestern portion of the country. No flood risk is expected during the month of June.

    Forecast

    The increased likelihood for the establishment of a positive Indian Ocean Dipole (IOD), coupled with moderately strong El-Nino events, is expected to influence below-average seasonal rainfall over much of Ethiopia and the eastern half of South Sudan, and with areas of average performance forecast over western Ethiopian highlands, according to the latest GHACOF64 consensus rainfall forecast, recently issued in late May. Meanwhile, much of the eastern Horn is likely to remain typically dry, apart from colder-than-normal conditions over the East Africa highlands during this period.

    The rainfall forecast for June is indicative of the timely onset and establishment of June to September seasonal rains over the western and central Ethiopian highlands, Sudan, and South Sudan. Figures 4 and 5 shows evidence of the consensus between weekly IRI/Sub-X and NMME monthly rainfall forecast in terms of areas of expected wetter-than-average conditions, shown in shades of green, over southwest Sudan, northeast South Sudan and parts of northwestern Uganda in June, with near-average for the rest of these countries. However, the East Africa’s coastal strip regions of northern Tanzania, Kenya and southern Somalia, together with parts of Uganda are likely to experience below average rainfall amounts in the month of June.

    The flood risks are more imminent over northern East Africa, owing to the forecast of above-average rainfall and persistently-saturated soils in coming weeks.

    Figure 4

    IRI Sub-X rainfall probability forecast for June 10 -23, 2023
    Map of East Africa showing IRI Sub-X rainfall probability forecast for June 10 -23, 2023

    Source: IRI/CPC

    Figure 5

    NMME June 2023 rainfall probability forecast, based on May initial conditions
    Map of East Africa showing NMME June 2023 rainfall probability forecast, based on May initial conditions

    Source: IRI/CPC

    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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