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Generally good cropping conditions for much of the Sahel, except over Senegal and Mauritania

  • Seasonal Monitor
  • West Africa
  • August 22, 2014
Generally good cropping conditions for much of the Sahel, except over Senegal and Mauritania

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  • Key Messages
  • Update on Seasonal Progress
  • Forecasts
  • Key Messages
    • There is a low level of skill in forecasting the remainder of the season over Senegal and Mauritania, though available information suggests average rainfall levels for the remainder of the season. Persistent dryness over northern Senegal and southwestern Mauritania earlier in the season, though, has the potential to significantly reduce rainfed crop harvests.

    • July rains brought much needed relief in the agro-pastoral areas of Chad and Niger making average crop production and pasture growth a possibility for this season.

    • May to July rainfall this season was generally above or close to average in the bi-modal zone and well distributed in time. An average to above average July maize harvest was, therefore, expected for southern, coastal countries.


    Update on Seasonal Progress
    • The northward progression of the Intertertropical Front (ITF) was on average slightly north or at its typical seasonal position in late July over Mali, Niger and Chad. Over Mauritania, however, its northward migration was slower than normal and it was two to three degrees of latitude south of its typical position.
    • With the ITF near or above its seasonal position over the  central and eastern Sahel, July rainfall was generally average to above average over Sahelian areas previously identified as having experienced significant rainfall deficits, particularly in Niger and Chad (Figures 1 and 2), bringing much needed relief to the area. On the contrary, drier than normal conditions continued to prevail in northwestern Senegal and southern Mauritania, as the ITF remained south of its climatological position.
    • July rainfall in the Bi-modal zone was above average. Over the Guinean-Sudanian zone, rainfall was average to above-average, including over the eastern part of Guinea Bissau, Guinea, Sierra Leone, the western part of Liberia, central Nigeria and most of the Central African Republic. Many parts of the Guinean-Sudanian zone did, however, experienced severe rainfall deficit in July. Such areas include northeastern Cote d'Ivoire, northern Ghana, the southern parts of Togo and Benin, the Western part of Niger State in Nigeria, southern Cameroon and the western part of CAR.
    • The impact of July rainfall on crop and pastures differs by zone:
      • In the Bi-modal zone a wetter than average July could disturb harvest activities as excessively wet harvests can become difficult to store. If these rains persist in August, though, it could also signal an early start of the second season for coastal countries.
      • In the Guinean-Sudanian Zone crop water requirements are met everywhere, including over areas with below-average rainfall, where despite relative deficits, total accumulation provides sufficient moisture for crop growth.
      • In the western part of the Sudanian-Sahelian Zone persisting dryness led to significant sowing and pasture regeneration delays. This could result in a significant production drop for pastures and rainfed crops and a prolonged lean season for pastoral households. For central and eastern parts of the zone moisture conditions in July were favorable for crops and pastures over most areas. According to field reports sowing had yet to take place as of the end of July over a few scattered pockets of limited size. Were they not able to sow their fields, it could have been too late for most indigenous crops to reach maturation by the end of the season. However, adequate harvests in these areas are still possible through the use of shorter cycle substitute crops, generally available through extension services.
    • According to the short and medium term forecasts from NOAA/CPC, moderate to heavy rainfall is generally expected during the fourth week of August and the first week of September over nearly the whole region. Relief is even expected over most of northern Senegal and southwestern Mauritania, which has suffered significant dryness. However, dryness is still expected to persist for the next two weeks over a few areas of limited extent in extreme northern Senegal and southwestern Mauritania. Should the forecast continued suppressed rainfall hold true, these persistently dryness pockets in Senegal and Mauritania could experience a significant drop in rainfed crop production or a complete failure.

    Forecasts

    Most forecast models indicate a continued warming trend for the tropical eastern Pacific Ocean Sea Surface Temperatures (SSTs), but chances of El Niño during the rest of the summer have decreased to below 50%. Therefore, no significant influence in rainfall pattern over West Africa is expected.

    The greatest SST influence on West African rainfall will be determined by the Gulf of Guinea and Eastern Tropical Atlantic SSTs that since late May have been tending toward a configuration that is favorable to the Sahel rainfall. The latest NOAA-CPC Northern American Multi-Model Ensemble seasonal forecast updated in early August calls for a wetter than average rainy season across the Sahel though the areas where the models have good forecast skill are limited to the agro-pastoral areas in Chad, Zinder, Maradi and Tahoua regions in Niger and the regions of Sikasso, Segou, Mopti and Koulikoro in Mali. As for the area of concern of northwestern Senegal and southwestern Mauritania the updated seasonal forecasts indicates climatology, though there is low skill in the model.

    Figures Figure 1. Total rainfall estimate (RFE) in mm, month of July

    Figure 1

    Figure 1.

    Source: USGS/FEWS NET

    Figure 2. Rainfall estimate (RFE) anomaly compared to the 2001-2010 mean, for the month July

    Figure 2

    Figure 2.

    Source: Source: USGS/FEWS NET

    Seasonal Calendar in a Typical Year

    Figure 4

    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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