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Erratic and below-average rainfall performance during the March to May season

  • Seasonal Monitor
  • East Africa
  • June 9, 2014
Erratic and below-average rainfall performance during the March to May season

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  • Key Messages
  • Seasonal Progress
  • Forecast
  • Key Messages
    • March to May rains have been erratic and well below-average in East Africa, particularly in parts of Kenya, Tanzania, eastern Ethiopia and central and northern Somalia.

    • Conversely, the main rainy season began early in much of South Sudan with above-average rainfall in April and May. Torrential rains in the Tanzanian Coastal Strip caused some flooding and resulted in property damage in the area.

    • The short-term rainfall forecasts for the next two weeks indicate a normal end to the March to May rainy season in most parts of the eastern Horn, as rains shift northwards. Moderate to heavy rains are forecast across the Rift Valley in Kenya and average rainfall is expected in most of Sudan and South Sudan.


    Seasonal Progress

    March to May seasonal rainfall performance was generally poor for both cropping and pastoral regions in East Africa with rainfall deficits across the region. Rainfall deficits were highest in the Rift Valley regions of Kenya, especially in TransMara, Narok and Kajiado, and the Mara, Mwanza and Shinyaga regions of Tanzania, which received less than 50 percent of average seasonal cumulative rainfall. In some areas, rainfall totals were the worst in 30 years. The eastern Somali pastoral zones of Ethiopia and the central and northern regions of Somalia also experienced significantly below-average seasonal rainfall with rainfall totals between 50 to 80 percent of normal. However, over the past weeks rains began to increase again over the eastern Somali region of Ethiopia and in central and northern Somalia, easing cumulative rainfall deficits.  Much of Rwanda, Burundi, southern Uganda, and central and northern Tanzania also received erratic rainfall, ranging between 50 to 80 percent of average seasonal rainfall.

    Conversely, South Sudan and southern regions of neighboring Sudan, and the coastal regions of northeastern Tanzania received well above-average rains from April to May. In Tanzania, heavy rainfall caused flooding, property damage, and disrupted transportation. The rest of the region received near-normal cumulative rainfall, but with erratic distribution which affected cropping conditions over the marginal agricultural areas in the eastern lowlands of Kenya and parts of southern Somalia cropping zones.

    Below-average rainfall performance coupled with hotter-than-normal (+2C to +3C) conditions during April and May, negatively impacted rangeland water and pasture resources and crop conditions. The eMODIS Normalized Vegetation Difference Index (NDVI) anomalies (Figure 2) indicate areas where vegetation conditions are drier-than-normal. The most significant negative anomalies occurred in the central Rift Valley, and western and central regions of Kenya, and the Mara region of Tanzania. NDVI anomalies were also observed in Rwanda and Burundi, southeastern South Sudan (Kapoeta) and the southwestern regions of the Southern Nations, Nationalities, and Peoples Region (SNNPR) in Ethiopia, although to a lesser extent. There is an increased likelihood for below-average agricultural production in these areas, as the long rains are expected to gradually subside in the coming weeks and shift into the northern sector of the Greater Horn of Africa (GHA) region. The Kenyan Ministry of Agriculture’s preliminary national maize production estimates suggest below-average harvests as a result of the poor rainy season.  Cropping conditions in Tanzania, Uganda and belg cropping areas of Ethiopia have recovered despite the early season concerns and are likely to realize near-average crop production. In Somalia, Rwanda and Burundi, rainfall deficits have caused concerns about below-average harvests in the coming months.

    South Sudan, southern Sudan and western Ethiopia have better than normal vegetation conditions because of above-average early season rains. With the increased likelihood for an El Niño event occurring starting in July and lasting through late 2014, the rainfall outlook for June to August raises new concerns of average to below-average rainfall over the northern sector of the GHA. The coming El Niño is also likely to result in wetter-than-average October to December short rains for the eastern Horn.


    Forecast

    The short-term rainfall forecasts for the next two weeks indicate a normal end to the March to May rainy season in most parts of the eastern Horn, as the rains shift northwards into Sudan, Ethiopia, South Sudan, northern Somalia, Djibouti, Eritrea and also over parts of western Kenya and Uganda. East Africa coastal areas are also likely to continue receiving moderate to very heavy rains during this period, especially along the Kenya/Tanzania/Somalia coastal regions. 

    The expected moderate to heavy rains in the coming weeks over western, Rift valley and central Kenya will help alleviate the current drier-than-normal conditions, especially over Narok and Kajiado districts of Kenya, including the Mara region of Tanzania.

    Although the current seasonal rains are expected to continue normally in South Sudan and Sudan, these will be of less intensity in the next two weeks reducing the flood risk in the flooded areas in these countries.

    In general, the consensus seasonal climate forecast for June to August, indicate average to below-average rainfall across the northern sector as a result of the anticipated potential impacts of the El Niño event during this period highlighted in FEWS NET’s East Africa Seasonal Alert.

    Figures Seasonal calendar for a typical year

    Figure 1

    Seasonal Calendar for typical year

    Source: FEWS NET

    Figure 1. ARC2 RFE anomalies in comparison to 1983 – 2009 averages: March 1-May 31, 2014

    Figure 2

    Figure 1. ARC2 RFE anomalies in comparison to 1983 – 2009 averages: March 1-May 31, 2014

    Source: National Oceanic and Atmospheric Administration (NOAA)

    Figure 2. eMODIS Normalized Vegetation Difference Index (NDVI) anomalies from the 2001 to 2010 average. May 21 - 31, 2014

    Figure 3

    Figure 2. eMODIS Normalized Vegetation Difference Index (NDVI) anomalies from the 2001 to 2010 average. May 21 - 31, 2014

    Source: U.S. Geological Survey (USGS)

    Figure 3. Global Forecasting System one week rainfall forecast (mm): June 3-10, 2014

    Figure 4

    Figure 3. Global Forecasting System one week rainfall forecast (mm): June 3-10, 2014

    Source: NOAA Global Forecasting System/ Climate Prediction Center (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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