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Delayed onset and early seasonal rainfall deficits worsen over eastern Horn

  • Seasonal Monitor
  • East Africa
  • November 5, 2016
Delayed onset and early seasonal rainfall deficits worsen over eastern Horn

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  • Key Messages
  • Seasonal Progress
  • Forecast
  • Partner
    Key Messages
    • Rainfall for the October to December season over the eastern Horn of Africa is significantly delayed and remains well below average over southern and southeastern Ethiopia, southern and central Somalia, and eastern and northeastern Kenya. Remote sensing products suggest pastoral conditions and vegetation conditions in marginal cropping areas are well below average. 

    • In western areas of the region such as Uganda, Burundi, Rwanda, and South Sudan seasonal rainfall performance has been generally favorable since mid-October, following either with either a timely or slightly delayed onset of season or dry spells in early to mid-October. However, there are some initial rainfall deficits around the Lake Victoria basin.

    • Rainfall forecasts for the coming week (November 6-13) suggest rainfall is expected to improve in many areas of the eastern Horn of Africa during the next week, and heavy rainfall is expected over Burundi, Rwanda, and northern Tanzania. However, the week-two forecast (November 14-21) indicates much lighter and erratically distributed rainfall over the eastern Horn. 

    Seasonal Progress

    In the eastern Horn of Africa, seasonal rainfall since the start of October has been delayed by 20 to 30 days and below average (less than 25 percent of average) in parts of southern and central Somalia, southern and southeastern Ethiopia, and eastern and central Kenya (Figure 1). The delayed onset, coupled with hotter-than-normal land surface temperatures, has resulted in exceptionally drier-than-normal vegetation conditions (below 70 percent of normal), especially over southern Somalia, southeastern Ethiopia and eastern Kenya (Figure 2).

    In many areas, these poor conditions are resulting in the second consecutive season of below-average rainfall, following poor Gu 2016 seasonal rains, particularly in southern Somalia, southeastern Kenya, and parts of southern Ethiopia. The delayed onset is likely to continue in some of these areas if the seasonal rains do not become fully established in the coming one to two weeks, which could worsen the drought-like conditions over the eastern Horn, with continued rapid depletion of water and pasture.

    In Uganda, Rwanda, Burundi, northwestern Tanzania, and parts of western Kenya, the seasonal rains had a timely onset in September. They have generally been average to above average, except rainfall deficits appeared over the Lake Victoria basin (-50 to -100 mm) during the month of October. 

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

    • In southern and central Somalia, eastern Kenya, and southern and southeastern Ethiopia, rainfall has been seasonal rainfall has been significantly delayed and below average, resulting in a prolonged period of dryness since May that typically ends with the onset of seasonal rains starting in October. Pasture, water sources, and cropping conditions in marginal producing areas in southern Somalia, eastern and northern Kenya, and southern and southeastern Ethiopia are likely to worsen if the October to December seasonal rains do not get fully established in the coming one to two weeks.
    • In eastern and western Sudan, eastern and northern South Sudan and Eritrea, rainfall for October was above average to average (100 to 150 percent of normal), similar to the overall performance throughout the June to September season. This has supported above-average cropping and rangeland conditions in most parts of these countries. However, during October, rainfall was slightly below average in parts of southwestern South Sudan and southwestern Ethiopia.
    • In the Democratic Republic of the Congo, the seasonal rains are generally established across the eastern region despite early season rainfall deficits. The rains are expected to remain moderate to very heavy, with fairly good prospects for cropping conditions in November.
    • In Rwanda and Burundi, increased rainfall during the last two weeks has improved cropping prospects since erratic rainfall and dry spells in mid-October caused some stress to crops. In general, crop development remains good and is likely to continue with the forecast of moderate to very heavy rains during the next two weeks.
    • In Uganda, the second rainy season in bimodal areas (September to December) has started on time with slight delays of 10 to 20 days in a few localized areas. However, the Lake Victoria basin of Uganda has experienced early season rainfall deficits, while rainfall has been above average in its western areas. Overall, cropping conditions are generally good for much of the bimodal areas of the country. In unimodal Karamoja, the area is receiving small amounts of rainfall as is typical between October and December.
    • In bimodal areas of northwestern Tanzania, Vuli (September to December) rainfall has been mixed since mid-October, with rainfall generally below average, except in some pockets where near or above average rains fell, following a delayed onset of rainfall in late September and early October. 



    The short-term NOAA/GFS rainfall forecast (Figure 3) for November 6-13, 2016, indicates an increased likelihood for a gradual intensification of the Deyr/short-rains season over southern Somalia, eastern Kenya and southern Ethiopia, which could help improve water sources and pasture regeneration. However, the week 2 forecast for November 14-21 indicates light and very erratically distributed rainfall is expected over most of these areas. Meanwhile, moderate to very heavy rains (20 mm to 200 mm) are forecast to continue for the next two weeks over DRC, Rwanda, Burundi, parts of central and western Uganda, and western Kenya, marking the establishment and intensification of the current seasonal rains. In northwestern Kenya and neighboring Karamoja region of northeastern Uganda, the forecast is for less rainfall, and conditions will generally remain sunny and dry as is typical. With the southward shift of the ITF, seasonal rains will cease in November in Ethiopia, Sudan, and Eritrea. Western Yemen is likely to receive moderate to heavy rains over localized areas in the coming weeks. 

    Figures Figure 1. ARC2 30-day rainfall estimate anomaly, percent of normal (1983-2009), Oct. 6-Nov 4, 2016

    Figure 1

    Figure 1. ARC2 30-day rainfall estimate anomaly, percent of normal (1983-2009), Oct. 6-Nov 4, 2016

    Source: CPC/NOAA

    Figure 2. eMODIS/NDVI anomaly (2001-2010), October 16-25, 2016

    Figure 2

    Figure 2. eMODIS/NDVI anomaly (2001-2010), October 16-25, 2016

    Source: USGS/FEWS NET

    Figure 3. Week 1 GFS rainfall forecast (mm), November 6-13, 2016

    Figure 3

    Figure 3. Week 1 GFS rainfall forecast (mm), November 6-13, 2016

    Source: CPC/NOAA

    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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