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Average to above-average rainfall continues across the region

  • Seasonal Monitor
  • West Africa
  • August 30, 2017
Average to above-average rainfall continues across the region

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  • Key Messages
  • UPDATE ON SEASONAL PROGRESS
  • FORECASTS
  • Key Messages
    • Total seasonal rainfall is above-average over most of the region (Figures 1 and 2) with the exception of few relatively small areas in the northern part of the Sahelian zone.

    • Rainfall deficits are minimal and are not expected to adversely affect crop development with the exception of the western part of the Senegal – Mauritania border area.

    • The western part of the Senegal-Mauritania border is the only area that suffers from both rainfall bad-time distribution (Figure 3)and severe seasonal deficit (Figure 2), a combination likely to hamper crop development in a significant way.

    • The medium-term forecast for the next two weeks (August 21th– September 4th) calls for moderate to heavy rains over the entire region, an indication of continued favorable agricultural conditions.


    UPDATE ON SEASONAL PROGRESS
    • The Intertropical Front’s (ITF) is now at its climatological position in its portion over Mali and Chad but about 1-1.5 degrees south of it in Mauritania and Niger.  It underwent a 2-3 degrees of latitude drop compared to its position of the first dekad of August (Figure 4).  However, the observed southward movement despite its relatively large size over Mali, Chad and Niger must be a part of normal fluctuations since it is too early for the southward retreat to start and also the medium term forecast calls for a significant amount of rainfall in the northern part of the region.
    • Based on the FAO desert locust early August update the situation is expected to remain calm for the rest of the season; despite favorable rainfall observed during the last couple of months over the breeding area extending from Mauritania to Chad only small scale breeding is expected.
    • The “minor dry season” in the bi-modal zone continues normally.  However, in the other agro-climatological zones rainfall continues in general to be favorable to crops and pastures.  Few small areas in the Sahel have experienced deficits, but no negative effects on crops and range are expected since deficits are mostly light and coupled with a good time distribution of rainfall.
    • The only area of concern is the western part of the Senegal-Mauritania border.  This is the only part of the region that has been experiencing severe rainfall deficits and 12-14 days of longest dry spell during the last 30 days as of August 20th.  This area has to be closely monitored to assess the impact of dryness on crop performance.

    FORECASTS
    • The short and medium-term NOAA/CPC’s forecasts call for moderate to heavy rains throughout the region for the next two weeks (Aug 21-Sep 4) with no expected dry spells.
    • For the next several two month periods (September-November and October-December), seasonal forecasts from the NOAA-NCEP) call for average to above-average rainfall over most of the region.
    Figures Figure 1: Total rainfall estimate (RFE) in mm, 1stdekad of April-2nd dekad of August

    Figure 1

    Figure 1: Total rainfall estimate (RFE) in mm, 1stdekad of April-2nd dekad of August

    Source: USGS/FEWS NET

    Figure 2: Rainfall estimate (RFE) anomaly compared to the 2006-2015 mean, 1st dekad of April -2nd dekad of August

    Figure 2

    Figure 2: Rainfall estimate (RFE) anomaly compared to the 2006-2015 mean, 1st dekad of April -2nd dekad of August

    Source: USGS/FEWS NET

    Figure 3: Consecutive dry days during the last 30 days as of August 20th

    Figure 3

    Figure 3: Consecutive dry days during the last 30 days as of August 20th

    Source: USGS/FEWS NET

    Figure 4: Intertropical Front (ITF) position compared to climatological average in 2nd dekad of August

    Figure 4

    Figure 4: Intertropical Front (ITF) position compared to climatological average in 2nd dekad of August

    Source: USGS/FEWS NET

    SEASONAL CALENDAR IN A TYPICAL YEAR

    Figure 5

    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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