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The season is progressing well with mostly average to above-average and well distributed rainfall

  • Seasonal Monitor
  • West Africa
  • August 27, 2020
The season is progressing well with mostly average to above-average and well distributed rainfall

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  • Key Messages
  • Update on Seasonal Progress
  • Forecasts
  • Key Messages
    • The Intertropical Front (ITF) continues its northward migration and is at its climatological position over most of the region.

    • The first two dekads of August rainfall has been characterized by good time distribution and any deficits have been mostly light to moderate (Figure 1 and Figure 2).

    • The minor dry season in the bimodal zone has been drier than average (Figure 1).


    Update on Seasonal Progress
    • The Intertropical Front (ITF) continues its northward seasonal migration and underwent a large advance during the first dekad of August and was positioned between 20 to 23 degrees north, about 2 to 3 degrees north of its climatological position east of longitude 5 degrees west.  During the second dekad of August it moved back to be around its climatological position east of north-central Mali and slightly south of it in the western part of north-central Mali and Mauritania.
    • During the first two dekads of August parts of the Sahelian zone received average to above average rainfall and heavy downpours resulted in river swelling and floods.  Many places in the region have experience flooding particularly along major rivers.  At the same time other parts of the Sahelian zone received below average rainfall.  However, most deficits ranged from light to moderate and rainfall time distribution was good over the entire zone (Figure 1 and Figure 2).  Areas affected by severe rainfall deficits included southwestern Mauritania, and northern and southwestern Senegal including the Gambia.
    • The western and eastern parts of the Sudanian-Guinean zone received mostly average to above average rainfall during the first two dekads of August period.  Areas affected by severe rainfall deficits included part of Ghana, western and eastern Nigeria and northern Cameroon (Figure 1 and Figure 2).  The western part of Sudanian-Guinean was also affected by poor rainfall time distribution during this period.  Dry spells of over 9 days were observed over western Liberia, northern Cote d’Ivoire, a large part of northern Ghana and most of the Sudanian-Guinean part of Nigeria and southern Cameroon.

    Forecasts
    • According to the short and medium term forecasts from CHC/UCSB and from NOAA/CPC above average rainfall is expected over the Sahelian and Saharan zone and no significant dry spells are expected within the next two weeks.
    • The NOAA-CPC Northern American Multi-Model Ensemble (NMME) seasonal forecast for the final two months of the season (September and October) generally predict climatology to increased chances for above average rainfall in September and climatology to an increased chance of below average rainfall in October.
    Figures Map of the first two dekads of August total rainfall estimate (RFE) anomaly compared to the 2009-2018 mean: A combination of

    Figure 1

    Figure 1.

    Source: NOAA/USGS/FEWS NET

    Map of The first two dekads of August longest dry spell (days): In the Guinean and Sudano Guinean zones areas of 12-20 days o

    Figure 2

    Figure 2.

    Source: NOAA/USGS/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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