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Average to above-average and well distributed rainfall over most of the region increased flood risks

  • Seasonal Monitor
  • West Africa
  • August 30, 2019
Average to above-average and well distributed rainfall over most of the region increased flood risks

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  • Key Messages
  • Update on Seasonal Progress
  • Forecasts
  • Key Messages
    • August’s above average rainfall (Figure 1) has brought needed relief in the western part of the Sahel.

    • Characterized by a good time distribution over most of the region (Figure 2) August rainfall has resulted in favorable moisture conditions for both crops and pastures.

    • August’s mostly above average and well distributed rainfall has resulted in increased flood risk (Figure 3).

    Update on Seasonal Progress
    • The ITF’s northward migration continued and is at the third dekad of August positioned between 16.1 at the eastern border of Chad and 22.1 degrees of latitude at 5 degrees of longitude west at Mali-Mauritania border. It is located 2-3 degrees north of its climatological position throughout the region.
    • Rainfall analysis indicates continued adequate and favorable moisture conditions for planted crops in the region including areas like Senegal and Mauritania where planting delays of up to 4 dekads have been observed. However, the mostly above average rainfall that prevailed particularly toward the end of August resulted in an increased risk for flooding in many basins of the region (Figure 3).  Should this rainfall trend continue into September significant crop damage from floods is to be expected.
    • The bimodal zone where the short dry season prevailed since late July has received a significant amount of rainfall during the third dekad of August.  This indicates the end of the short dry season and the beginning of the minor rainy season (August to October).  Moisture conditions are favorable for planting at this start of the minor season.
    • The monthly forecasts from NOAA/CPC calls for  slight chances for below average rainfall over the western part of the Sahel (southern Mauritania-Senegal), slight chances for above average rainfall in parts of Mali and Niger and climatology elsewhere.  This forecast suggest that the flooding threat will subside.

    • The seasonal forecast from NOAA-NCEP for the next three-month period (September to November) calls for above-average rainfall over most of the Sahelian part of the region from Mali to Chad, Nigeria and the northern parts of Cote d’Ivoire, Ghana, Togo and Benin.
    Figures Map of Total August rainfall estimate (RFE) anomaly with respect to the 2007-2016 mean: Mostly above average with some areas

    Figure 1

    Figure 1.

    Source: USGS/FEWS NET

    Map of Total August Rainfall estimate (RFE) anomaly and dry spells: noted in southern Mauritania/Senegal, and the Gulf of Gui

    Figure 2

    Figure 2.

    Source: USGS/FEWS NET

    Map of Basin Excess Rainfall Map – August Dekad 3, 2019: Noted throughout the Sahel, with very high figures in northern Mali,

    Figure 3

    Figure 3.

    Source: USGS/FEWS NET

    West Africa seasonal calendar  In the North, Main season cultivation is from mid-May to mid-August. Main harvest is from mid-

    Figure 1


    Source: FEWS NET

    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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