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Early-season rainfall deficits impact vegetation in southern Somalia and eastern Kenya

  • Seasonal Monitor
  • East Africa
  • November 14, 2014
Early-season rainfall deficits impact vegetation in southern Somalia and eastern Kenya

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  • Key Messages
  • Seasonal Progress
  • Forecast
  • Partners
    NOAA
    USGS
    Key Messages
    • Drier-than-normal conditions persist in eastern Kenya and southern Somalia despite moderate to heavy rainfall in the first dekad of November. 

    • Flooding over the Shabelle and Juba River Basins continued to damage crops and homesteads in southern Somalia and in the Dassench and Kangatom areas of the South Omo Zone of Ethiopia. 

    • Intensifying rains forecast over the eastern Horn in the coming weeks will replenish rangeland and crop resources. However, localized, very heavy rains are likely over this region, increasing the threat of flash floods, especially over northeastern Kenya, southern Somalia and parts of the Somali region of Ethiopia.


    Seasonal Progress

    Significant cumulative rainfall deficits of up to 50 millimeters (mm), and poor spatial rainfall distribution affected early season rainfall performance in parts of southern Somalia, northeastern and eastern Kenya, and along coastal areas of Tanzania (Figure 1).

    In cropping regions of eastern Kenya and southern Somalia, the onset of rains occurred two to three dekads later than normal. Late rains were caused by the very slow development of El-Nino, in addition to persistent Indian Ocean Dipole (IOD) neutral conditions, which often cause average to below-average rainfall performance over this region.  

    Seasonal rains gradually recovered by the first dekad of November due to the rapid and abnormal warming of Indian Ocean sea surface temperatures off the East African coast in recent weeks.  Moderate to heavy rains over the eastern Horn of Africa eased the prolonged dry season but drier-than-average conditions persisted over southern Somalia and eastern Kenya. The Normalized Difference Vegetation Index (NDVI) shows several areas where rangeland or crop conditions were below-average (Figure 2) in the first dekad of November. In southern Somalia and eastern Kenya, the NDVI was less than 80 percent of normal. Prolonged dryness and abnormally high temperatures (+2 degrees Celsius) continue to stress rangeland resources in these areas. 

    Unseasonable, above-average rains continued in the northern and western sectors in October and early November, enhancing vegetation conditions in Ethiopia, Sudan, South Sudan, Western Kenya, and Uganda (Figure 2). Some areas received rainfall surpluses of more than 100 mm.

    Well above-average rains in the eastern Ethiopian Highlands caused flooding over the Shabelle and Juba River Basins in October and early November. Flooding in these areas damaged crops and homesteads in southern Somalia and in the Dassench and Kangatom areas of the South Omo Zone of Ethiopia.  Deyr rains in Ethiopia have been average since their onset in early October, except in localized areas of the South Omo Zones in Ethiopia.

    Unseasonably heavy rainfall in Western Kenya and Uganda negatively impacted maize harvesting and drying. Moisture surpluses are likely to cause post-harvest losses and delay planting in second-season cropping areas.

    In Rwanda and Burundi, rains improved in late October and early November, following a delayed onset of Season A rains, particularly in northwestern regions of Rwanda. Above-average rainfall over the past two dekads improved conditions for planted maize, and enabled crop development, currently in early vegetative stages.   

    Harvests prospects are positive in much of the region. Bumper harvests are expected in Tanzania. Mid-season assessments in Sudan estimate 2014/15 production to be 30 percent above average. Average maize and sorghum harvests are expected in Ethiopia and areas in South Sudan unaffected by conflict.

    Harvests will be well below average in the conflict-affected Greater Upper Nile region of South Sudan due to significant reductions in area planted. In Kenya, maize production deficits of between 20 to 30 percent are expected. 


    Forecast

    Short-term forecasts indicate moderate to heavy rains for Ethiopia, Uganda, Rwanda, and Burundi; and across western Kenya into western and southern Tanzania over the next two weeks. Between 20 and 125 mm of rainfall are expected in these areas (Figure 3).  

    Widespread moderate to fairly heavy rains (10-100 mm) are forecast over the eastern Horn, marking the establishment of its seasonal short-rains. These rains are expected to help ease current cumulative rainfall deficits and support the replenishment of rangeland resources, including pasture and surface water. Rains will also enable planting in southern Somalia, and in the eastern and southeastern lowlands of Kenya.

    However, localized, episodic very heavy rains are likely over this region, increasing the threat of flash floods in the coming weeks, especially over northeastern Kenya, southern Somalia and parts of the Somali region of Ethiopia.

    Recently updated seasonal forecasts from the IGAD Climate Prediction and Applications Center (ICPAC) indicate a gradual development of a mild El-Nino event, increasing the likelihood for normal to slightly below-normal rainfall performance over eastern Horn for the remainder of the 2014 November to December short-rains season. 

    Figures Figure 1. Rainfall (RFE) anomalies in millimeters (mm) from the 1983 to 2009 mean, October 1 to November 11, 2014

    Figure 1

    Figure 1. Rainfall (RFE) anomalies in millimeters (mm) from the 1983 to 2009 mean, October 1 to November 11, 2014

    Source: FEWS NET/ NOAA

    Figure 2. eMODIS Normalized Difference Vegetation Index (NDVI) as a percent of the 2001 to 2010 mean, November 1-10, 2014

    Figure 2

    Figure 2. eMODIS Normalized Difference Vegetation Index (NDVI) as a percent of the 2001 to 2010 mean, November 1-10, 2014

    Source: FEWS NET/USGS

    Figure 3. GFS rainfall forecast in mm for November 11 to 26, 2014

    Figure 3

    Figure 3. GFS rainfall forecast in mm for November 11 to 26, 2014

    Source: FEWS NET/ 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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