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Above average and well distributed rainfall prevailed most of the season

  • Seasonal Monitor
  • West Africa
  • September 23, 2019
Above average and well distributed rainfall prevailed most of the season

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  • Key Messages
  • Update on Seasonal Progress
  • Forecasts
  • Key Messages
    • The ITF started its southward retreat in early September and is now at the northern limit of the Sahelian zone (Figure 1), which augurs the normal end of rains in the northern Sahelian zone in late September.

    • With well distributed rainfall (Figure 2) the slight to moderate deficits (Figure 3) affecting the western part of the Sahel will not negatively impact crop growth and development.

    • The delayed growing season has resulted in very slow development of natural vegetation (Figure 4), which may have a negative impact on pasture production in the western part of the Sahel.

    • The bi-modal zone received above average rainfall meaning minor season crops have favorable moisture conditions (Figure 2).

    Update on Seasonal Progress
    • The Intertropical Front’s (ITF) has reached its northernmost position in late August and started its southward retreat during the first dekad of September.  It’s is now positioned between 14.6 degrees of latitude at the eastern border of Chad and 20.8 degrees at 10 degrees of longitude west in Mauritania.  It’s at its climatological position over eastern Mali, Niger and Chad and north of it over western Mali and Mauritania (Figure 1).  This indicates the end of the rainy season in the northern part of the Sahelian zone is nearing.
    • Since the end of the “minor dry season” in late August the bi-modal zone has been receiving well distributed and above average rainfall (Figure 2 and Figure 3).  Crops in this area, therefore, have been in favorable agrometeorological conditions.  The October seasonal forecast suggests partly slight chances for above average rainfall and partly climatology.  Therefore, the favorable agrometeorological conditions that have prevailed so far during the minor season will continue until the end.
    • For the other agro-climatological zones north of the bi-modal zone rainfall was generally above average until the end of August.  The few areas with below average rainfall only experienced light deficits and benefited from a nice time distribution of rainfall resulting into favorable conditions for crops and pastures at the exception of the western part of the Sahelian zone.
    • It is the third consecutive season that the western part of the Sahel and particularly Senegal has experienced a bad start of the growing season characterized by severe deficits and badly distributed rainfall resulting into significant planting delays.  The impact of this bad start of the growing season seems to be worst in the current season because of the delayed development of the natural vegetation as shown by the NDVI curves (Figure 4) over the pastoral areas of Senegal.  Current season vegetation has been below average and below the last two years.  The ITF being still at 20 degrees of latitude north in the western part of the Sahel is good sign that the area will continue receiving rain in the next few dekads.  However, chances for the natural vegetation recovery to its average level are very slim even if the end of the rainy season is delayed.
    • Based on the FAO desert locust update the situation is expected to remain calm for the rest of the season. The small-scale breeding reported in recent past is expected to decline except in northwestern Mauritania, but this increase will remain limited and no threat is expected in the coming months.


    • The NOAA-NCEP seasonal forecast using August initial conditions (no update for September) indicates slight chances for above average rainfall over some parts of the region and climatology over the rest.
    Figures Map of the ITF position, second dekad of September: Slightly below average in the west and near average in the center and eas

    Figure 1

    Figure 1.

    Source: USGS/FEWS NET

    Map indicating areas with :  Longest dry spell during the first 20 days of September : Most of the region has had little to n

    Figure 2

    Figure 2.

    Source: USGS/FEWS NET

    Map of Total (1-20 September) rainfall estimate (RFE) anomaly compared to the 2007-2016 mean: much of the region is in slight

    Figure 3

    Figure 3.

    Source: USGS/FEWS NET

    Graphs of NDVI in pastoral areas of Senegal: In all indicated areas (Matam, Ranerou Ferlo, and Kanel) the 2019 NDVI is less t

    Figure 4

    Figure 4.

    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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