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The Intertropical Front has begun its seasonal southward retreat. Due to cooler than average Gulf of Guinea sea surface temperatures, the timing of its retreat is expected to progress at a typical to slower than normal rate. In the northern Sahel the end of season has extended through the end of September, providing enough time for most crops to complete their cycle despite early seasonal delays.
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Crop and pasture production in the Sahel is expected to be near average for most of the region, even in central and eastern zones that experienced a delayed start of season, as good rainfall since July and a typical to late end of season will contribute to making up rainfall deficits experienced earlier in the season.
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Continued dryness in the Bi-modal zone following the typical first season break indicate a delayed start to the second season, which could have implications for second season harvests in the Bi-modal zone.
- At the beginning of the West Africa monsoon season, between early May and the end of June, warmer than average Gulf of Guinea Sea Surface Temperatures (SSTs) and moderate impacts from El Niño resulted in late (Figure 3), poorly distributed and below-average rainfall over most of the region. Beginning in July, however, cooler than average Gulf of Guinea SSTs contributed to maintaining the Intertropical Front (ITF) at or north of its climatological position over most of the region. The ITF is the leading edge of the Intertropical Convergence Zone, which is the weather pattern that brings rain to West Africa in the northern hemisphere summer. The ITF maintaining a position at or north of its climatological position since earl July has resulted in average to above-average seasonal rainfall totals across the Sahel and Sudano-Guinean zone (Figure 1 and Figure 2).
- Although the start of season was late for much of the Sudano-Guinean zone and southern Sahel, the start of season was 1 to 3 weeks early over most of the northern Sahel. Rainfall deficits that persisted in this area were generally light. The areas of West Africa where moderate seasonal rainfall deficits still persist are relatively small in size and are in central-southern Mauritania, in southern Gao in Mali, in northern Maradi and northwestern Zinder regions in Niger, and across a few areas in Chad spanning from Kanem to Wadi Firra (Figure 2). Severe rainfall deficits in the region could only be seen in the Bi-modal zone. These deficits could be in part explained by a longer and more pronounced August dry season than normal, which also resulted in a delayed start of the second season.
- Consequences and effects on crop development of the last 30 days rainfall situation vary by agro-ecological zone:
- Moisture conditions are favorable for continued good crop development across the northern Sahel, where cumulative rainfall totals since early July are above average. For the areas showing slight to moderate deficits from Mali eastward, crop and/or pasture production is not expected to be affected very significantly as rains continued through the end of September. Continued rainfall in mid-October in Senegal and southern Mauritania is expected to contribute to alleviating deficits experienced at the beginning of the season.
- Generally good cropping conditions have continued over the southern part of the Sudano-Sahelian zone and the Sudano-Guinean zones despite the significantly late start of season that affected parts of the regions. Continued above-average rainfall since July with good spatial and temporal distribution is expected to compensate for the effects of deficits experienced earlier in the season.
- Pronounced dryness observed in the Bi-modal zone during the August break persisted through September, delaying the start of the second season, increasing the risk for a bad second season harvest, which would begin between late November and early December.
- Gulf of Guinea SSTs are currently and forecast to remain cooler than average for the next few weeks. As such, the ITF’s southward retreat is expected to be normal or slightly slower than normal, bring a typical to late end of season for most of the region. In the northern Sahel, the season has reached its end in most areas, whereas in the Sudano-Guinean zone seasonal rains will likely continue until early November.
- Global Forecast System (GFS) forecasts through the end of October indicate below-average to average accumulation in the Bi-modal zone.
Figure 1
Figure 1.
Source: USGS/FEWS NET
Figure 2
Figure 2.
Source: USGS/FEWS NET
Figure 3
Figure 3.
Source: USGS/FEWS NET
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.