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Mostly normal start of season with average or better, well distributed rainfall

  • Seasonal Monitor
  • West Africa
  • May 16, 2017
Mostly normal start of season with average or better, well distributed rainfall

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  • Key Messages
  • UPDATE ON SEASONAL PROGRESS
  • FORECASTS
  • Key Messages
    • The onset of the long season (March to July) rains occurred in early March in the bi-modal zone and gradually expanded northward following the ITF migration to reach the Sudanian-Guinean zone in April and southern Sahelian zone in late April-early May.

    • Conditions for wet sowing/planting were normally on time in mid-March for the bi-modal areas, generally on time or a little earlier in April for the Sudanian-Guinean zone, and in early May for the Sahelian zone.

    • Agrometeorological conditions have generally been favorable since mid-March for normal development of planted crops in the bi-modal and Sudanian-Guinean zones with the exception of the extreme western part of the zone where the season has yet to start. 


    UPDATE ON SEASONAL PROGRESS
    • The ITF’s (Intertropical Front) northward migration started in early March and is now positioned between 12.0 and 15.0 degrees latitude in early May.  It is located at or slightly north of its climatological position over West Africa, with the exception of eastern Chad where it is located south of its climatological position.
    • Over the bi-modal zone and Sudanian-Guinean zones, where the growing season has been in progress for over a month, total rainfall amounts (Figure 1) in the first dekad of April to the first dekad of May are mostly average to above average (Figure 2).  Small portions of these two zones, however, have been affected by below average rainfall with deficits ranging from light to moderate.  Areas affected by moderate deficits include portions of Ghana, Cote d'Ivoire and Liberia.  However, even in these areas, deficits have been offset by a fair time distribution of rains, which resulted in a timely or slightly delayed start of the season.
    • Over portions of the southern part of the Sahelian zone (southern Mali, Burkina Faso, northern parts of Benin, Cameroon, and Nigeria and the southern part of Chad) the late April - early May rainfall for wet sowing conditions occurred earlier than normal.
    • The adequate moisture conditions that have prevailed so far have been favorable to the development of planted crops in the Bi-modal, Sudanian-Guinean and in the southern Sahelian zones with the exception of portions of northern Ghana, and southern Chad.  The early season, mostly above-average rainfall in the Sahelian zone, has allowed the start of the season to take place earlier than normal over most of the southern part of the zone.
    • According to the short and medium term forecasts from NOAA/CPC, rainfall is expected to expand northward normally and will continue for the next two weeks without dry spells.  This forecast calls for moderate to heavy rains throughout the part of the region where the growing season is in progress and the southern part of the Sahelian zone with the exception of eastern Burkina Faso and southeastern Chad where dry conditions are expected in the next two weeks.

    FORECASTS
    • The seasonal forecast from NOAA-NCEP for the next three-month periods (June-August, July-September and August-October) calls for above average rainfall over most of the Sahel and the Gulf of Guinea countries.
    Figures Figure 1.Total rainfall estimate (RFE) in mm, 1stdekad of April to 1stdekad of May

    Figure 1

    Figure 1.Total rainfall estimate (RFE) in mm, 1stdekad of April to 1stdekad of May

    Source: USGS/FEWS NET

    Figure 2. Rainfall estimate (RFE) anomaly compared to the 2006-2015 mean, 1stdekad of  April to 1stdekad of May

    Figure 2

    Figure 2. Rainfall estimate (RFE) anomaly compared to the 2006-2015 mean, 1stdekad of April to 1stdekad of May

    Source: USGS/FEWS NET

     SEASONAL CALENDAR IN A TYPICAL YEAR

    Figure 3

    SEASONAL CALENDAR IN A TYPICAL YEAR

    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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