The African Monsoon Recent Evolution and Current Status

The African Monsoon Recent Evolution and Current Status Update prepared by Climate Prediction Center / NCEP 20 September 2010 For more information, visit: http: //www. cpc. ncep. noaa. gov/products/Global_Monsoons/African_Monsoons/precip_monitoring. shtml

Outline • Highlights • Recent Evolution and Current Conditions • NCEP GEFS Forecasts • Summary

Highlights: Last 7 Days • During the past seven days, moderate to heavy rains persisted over Senegal and parts of Mali and Burkina Faso resulting in flooding in some localities. • Light rains persisted and sustained moisture deficits over north central Nigeria.

Rainfall Patterns: Last 7 Days During the past seven days, rainfall diminished significantly over Mauritania. However, moderate rains sustained moisture surpluses and flooding potentials over northern Senegal, and parts of southern Mali and northern Burkina Faso. Rainfall was near average over most areas in the Gulf of Guinea region. However, light rains sustained moisture deficits over north central Nigeria. Rainfall was also below average over portions of central Africa and southern Sudan. Moderate showers resulted in above average rains in portions of central Ethiopia.

Rainfall Patterns: Last 30 Days During the past 30 days, rainfall was above average over most parts of Mauritania and Senegal, southern and central Mali, Guinea, Liberia, Burkina Faso, southern Niger, Benin, Togo and northern Cote d’Ivoire. Rainfall was below average over Sierra Leone and the southern areas of Cote d’Ivoire and Ghana. Huge rainfall deficits were recorded locally over Nigeria. In central Africa, rainfall was above average over central Chad, parts of CAR, central Sudan and central and eastern Ethiopia. Rainfall was below average over southern Sudan and Chad, most parts of DRC, Cameroon and southern Africa.

Rainfall Patterns: Last 90 Days During the past 90 days, rainfall was above average over most parts of Senegal and Guinea, southern Mauritania, Mali, Burkina Faso, Niger, and most parts of Cote d’Ivoire. Rainfall was below average over Sierra Leone, parts of Liberia, Ghana and Benin and most parts of Nigeria. In central and eastern Africa, rainfall was above average over southern Chad, most of CAR, northern part of Congo, central and eastern Ethiopia, and southeastern Cameroon. Rainfall was below average over most of Cameroon, DRC, Sudan, and Uganda.

Rainfall Patterns: Last 180 Days During the past 180 days, rainfall was above average over most areas in West Africa, except for portions of Sierra Leone, southern Ghana, northern Benin and most parts of Nigeria. In central Africa, rainfall was above average over southern Chad, CAR, southeastern Cameroon, Gabon, and the northern areas of Congo and DRC. Rainfall was also above average over central and eastern Ethiopia and the southern tip of Somalia. Rainfall was below average over most areas in eastern DRC, central Sudan, locally in southern Tanzania, and eastern Madagascar.

Recent Rainfall Evolution Daily evolution of precipitation at selected stations indicates that persistent rains over the past several weeks sustained moisture surpluses over western Senegal (lower panel – left). Steady but lighter than average rains resulted in moisture deficits in northern Nigeria (upper panel – right). Above average rains persisted over western Ethiopia (lower panel – right ).

Atmospheric Circulation: Last 7 Days The 850 h. Pa wind anomaly (left panel) reflected westerly wind anomalies over West Africa with a trough over the Gulf of Guinea and a ridge over Nigeria. A ridge over Algeria and Morocco into the Sahel perturbed the western flank of the ITCZ. The 200 h. Pa wind anomaly (right panel) featured a strong upper level ridge across northwestern Africa. This pattern combined with the low level conditions as featured in the 850 h. Pa wind anomaly contributed to the initiation and amplification of convection and precipitation in West Africa.

NCEP GEFS Model Forecasts Non-Bias Corrected Probability of precipitation exceedance Week-1: Valid 21 - 27 September, 2010 Week-2: Valid 28 September- 04 October, 2010 For week-1 and wek-2, there is a high chance for precipitation to exceed 50 mm along the Gulf of Guinea coast and portions of central Africa (week-1).

Experimental Week-1 Precipitation Outlooks Week-1 Outlook 21 – 27 September, 2010 1. There is an increased chance for above average precipitation over parts of West Africa: The anomalous westerly flow from the Atlantic Ocean will feed moisture into the westward convective systems and result in enhanced rainfall activity. Confidence: Moderate 2. There is an increased chance for below average rainfall over parts of northern Nigeria: Low level easterly wind anomalies with their associated anticyclonic turning are expected to suppress rainfall in this region. Confidence: Moderate.

Experimental Week-2 Precipitation Outlooks Week-2 Outlook 28 - 4 October, 2010 No forecast – Climatology suggested.

Summary • During the past seven days, rainfall diminished significantly over Mauritania. However, moderate rains sustained moisture surpluses and flooding potentials over northern Senegal, and parts of southern Mali and northern Burkina Faso. Rainfall was near average over most areas in the Gulf of Guinea region. However, light rains sustained moisture deficits over north central Nigeria. Rainfall was also below average over portions of central Africa and southern Sudan. Moderate showers resulted in above average rains in portions of central Ethiopia. • During the past 30, rainfall was above average over most parts of Mauritania and Senegal, southern and central Mali, Guinea, Liberia, Burkina Faso, southern Niger, Benin, Togo and northern Cote d’Ivoire. Rainfall was below average over Sierra Leone and the southern areas of Cote d’Ivoire and Ghana. Huge rainfall deficits were recorded locally over Nigeria. In central Africa, rainfall was above average over central Chad, parts of CAR, central Sudan and central and eastern Ethiopia. Rainfall was below average over southern Sudan and Chad, most parts of DRC, Cameroon and southern Africa. • During the past 90 days, rainfall was above average over most parts of Senegal and Guinea, southern Mauritania, Mali, Burkina Faso, Niger, and most parts of Cote d’Ivoire. Rainfall was below average over Sierra Leone, parts of Liberia, Ghana and Benin and most parts of Nigeria. In central and eastern Africa, rainfall was above average over southern Chad, most of CAR, northern part of Congo, central and eastern Ethiopia, and southeastern Cameroon. Rainfall was below average over most of Cameroon, DRC, Sudan, and Uganda. • For week-1, There is an increased chance for above average precipitation over the western end of West Africa. There is an increased chance for below average rainfall over parts of northern Nigeria