Global Information and Early Warning System
THE RAINY SEASON IS STARTING ON TIME IN THE CENTRE AND THE EAST OF THE SAHEL. DESERT LOCUSTS ARE MOVING FROM NORTH-WEST AFRICA SOUTHWARDS IN THE WEST AND THE CENTRE.
Rains started in April in Burkina Faso and became abundant over the south and the centre in May. The rainy season started in May in the south of Chad, Guinea Bissau, Mali and the extreme south of Niger. First rains were registered in early June in southern Senegal and The Gambia. Rainfall became quite abundant in early June over most producing areas. Land preparation and plantings are progressing following the onset of the rains. Seasonably dry conditions prevail in Cape Verde, Mauritania and northern parts of Senegal.
The last Meteosat image for the first dekad of June indicates that cloud coverage moved northwards and westwards but cloud duration, and therefore intensity of the rains, decreased in southern Mali and Burkina Faso. Rains should have started in southern and central-eastern Senegal, The Gambia, most parts of western Mali, and the extreme north of Burkina Faso. They were quite abundant over the main producing areas of Niger, allowing the start of planting, and progressed northwards in central Chad. By contrast, rainfall decreased in southern Mali and in southern and central Burkina Faso.
Significant movement of Desert Locusts from the spring breeding areas of North-West Africa towards the summer breeding areas of the Sahel were reported during May. There were several reports of swarms arriving in Mauritania, Senegal, Mali and Niger. There was also an unconfirmed report from Burkina Faso. Movements of additional adult groups and few small swarms could be expected in these countries, while there is a low to moderate risk of further movement eastward into Chad during June. Adults are expected to lay eggs once the rains commence.
In these reports, reference will be made to four different eco-climatic zones based on the average annual precipitation and agricultural features, i.e. Sahelian zone, Sudano-Sahelian zone, Sudanian zone and Guinean zone. They are shown in the map and described below:
Sahelian zone: Where average annual precipitation ranges between 250 and 500 mm. This zone is at the limit of perennial vegetation. In parts where precipitation is less than 350 mm, only pastures and occasional short-cycle drought-resistant cereal crops are grown; all cropping in this zone is subject to high risk.
Sudano-Sahelian zone: Where average annual precipitation ranges from 500 to 900 mm. In those parts of this zone where precipitation is less than 700 mm, mostly crops with a short growing cycle of 90 days are generally cultivated predominantly sorghum and millet.
Sudanian zone: Where average annual precipitation ranges from 900 to 1 100 mm. In this zone, most cereal crops have a growing cycle of 120 days or more. Most cereals, notably maize, root and cash crops are grown in this zone.
Guinean zone: Where average annual precipitation exceeds 1 100 mm. Guinea-Bissau and a small area of southern Burkina Faso belong to this zone, more suited to root crop cultivation.
Reference will also be made to the Intertropical Convergence Zone (ITCZ), also known by its trace on the earth's surface, called the Intertropical Front. The ITCZ is a quasi-permanent zone between two air masses separating the northern and southern hemisphere trade winds. The ITCZ moves north and south of the equator and usually reaches its most northerly position in July. Its position defines the northern limits of possible precipitation in the Sahel; rain-bearing clouds are generally situated 150-200 km south of the Intertropical Front.