SAHEL WEATHER AND CROP SITUATION 1999Global Information and Early Warning System on food and agriculture
Report No 1 - 16 June 1999
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The rainy season started generally on time or even early in southern Senegal. However, following generally above normal rains in early to mid-May, the rains decreased significantly in early June in the centre and the east of the Sahel. By contrast, in the west, they progressed northwards over Senegal, The Gambia and Guinea Bissau. The rainy season started in April in the extreme south of Mali and progressed northwards in May. In Burkina Faso, rains started in mid-April, became widespread and were generally above normal over the south and the centre up to mid-May, but they decreased significantly in early June. Precipitation was widespread over southern Niger and Chad in May but decreased in early June. Elsewhere, in Cape Verde, northern parts of Senegal and Mauritania, seasonably dry conditions prevail. The last Meteosat satellite image for the first few days of the second dekad of June confirms the rainfall pattern.
Land preparation and plantings are in progress following the onset of the rains. Crops are emerging satisfactorily in Burkina Faso, southern Chad and Mali but reduced rains in early June are threatening recently planted crops, notably in Burkina Faso.
Grain-eating birds are reported in Chad, Mali and Niger. Control measures are
underway. Rodents also appeared following plantings in Niger. Isolated Desert
Locusts have been reported in Mauritania; low numbers are expected in the summer
breeding areas of the Sahel once seasonal rains commence. No significant developments
Two meetings have been held in Dakar to prepare the monitoring of 1999 growing season in the Sahel.
From 7 to 9 June, the ACMAD (African Centre of Meteorological Applications for Development) and the Agrhymet Centre of CILSS hosted the Second Forum on Seasonal Climate Prediction (PRESAO) to formulate guidance on the expected rainfall for the period July-September 1999 over West Africa, Sudan and Ethiopia. The Sahelian region receives about 80 percent of its annual precipitation in the months July-September. The Forum reviewed the likely impact on the region's climate of La Niña event (1998-99), which is forecast to develop during the coming months, and of the warmer than normal tropical South Atlantic sea surface temperature. A seasonal weather forecast has been made based on atmospheric models together with physically based statistical models. The model estimates the probability of this year's total rainfall falling in one of three categories (above normal, below normal and near normal) defined using the recorded rainfall in the 1961-90 period.
For the central and eastern Sahelian region, extending from Mali eastward, there is an increased probability this year of near normal to above normal rainfall totals. In contrast, for the western Sahelian region covering most parts of Mauritania, Senegal and extending southward to Guinea, the probability of near normal to below normal conditions is increased. For the region extending from Sierra Leone to Central Nigeria, there is an increased probability of the above normal rainfall category occurring. Further east in south-eastern Nigeria and southern Cameroon, the most likely rainfall category this year is near normal
From 10 to 12 June, the CILSS (Comité inter-Etats de Lutte contre la Sécheresse
au Sahel) hosted a regional technical meeting to review the current situation
at the start of the rainy season in the Sahel. After the presentation of the
final production figures and updated cereal balance sheets, the participants
reviewed on-going assistance programs and discussed the monitoring of 1999 growing
season. A regional meeting is scheduled around mid-September to undertake a
pre-assessment of 1999 crop outlook before the usual FAO/CILSS Crop Assessment
Missions in October. An additional session permitted presentation and discussion
of the final report of a working group on information systems on food security
in the Sahel (SISAS) and further activities on the subject.
BURKINA FASO CAPE-VERDE CHAD GAMBIA GUINEA-BISSAU
MALI MAURITANIA NIGER SENEGAL
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.