The African Monsoon Recent Evolution and Current Status

The African Monsoon Recent Evolution and Current Status Include Week-1 and Week-2 Outlooks Update prepared by Climate Prediction Center / NCEP 28 May 2013 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 • Weekly total rainfall exceeded 150 mm over portions of Western Ethiopia. • Suppressed rainfall prevailed over many places in central Africa and the Lake Victoria regions, while local areas in the Gulf of Guinea countries received above average rainfall. • Week-1 outlooks call for an increased chance for above-average rainfall over Guinea-Bissau, Guinea Conakry and parts of Liberia. In contrast, there is an increased chance for below-average rainfall across portions of southern Mali and Burkina Faso.

Rainfall Patterns: Last 7 Days During the past seven days, rainfall was above-average over portions of Guinea, Sierra Leone, Cote D’Ivoire, western Burkina Faso, southern Benin, southern Nigeria, local areas in Cameroon, southern Chad, portions of South Sudan, and western Ethiopia. In contrast, much of Liberia, local areas in Mali, parts of Ghana and Burkina Faso, Nigeria, Cameroon, much of Gabon, Congo, CAR, portions of DRC, much of Uganda, eastern South Sudan, and local areas in Kenya and Ethiopia had below-average rainfall.

Rainfall Patterns: Last 30 Days During the past 30 days, below-average rainfall was observed over western Liberia, parts of Mali, local areas in Guinea, southern Ghana, Burkina Faso, much of Nigeria, portions of Cameroon, local area in Congo and DRC, northern Tanzania, portions of Kenya, and southern Ethiopia. In contrast, local areas in Guinea, Cote D’Ivoire, Benin, northern Cameroon, parts of Gabon and Congo, CAR, portions of DRC, South Sudan, western Ethiopia, and local areas in Kenya, Tanzania and southern Somalia received above-average rainfall.

Rainfall Patterns: Last 90 Days During the past 90 days, parts of Cote D’Ivoire, Togo and Benin, western Gabon, much of CAR, parts of Angola and DRC, Ethiopia, western Kenya, southern Somalia, and local areas in Madagascar received above-average rainfall. In contrast, rainfall was belowaverage over parts of Nigeria, southern and eastern Angola, portions of Zambia and Namibia, Botswana, southern Tanzania, northern Mozambique and many parts of Madagascar.

Rainfall Patterns: Last 180 Days During the past 180 days, rainfall was above-average over parts of Cote D’Ivoire, Togo, Benin, western Gabon, much of CAR, northwestern DRC, local areas in South Sudan, parts of Ethiopia, Kenya, southern Somalia, Uganda, local areas in Tanzania, central and southern Mozambique, local areas in Zimbabwe, eastern South Africa, Lesotho, Swaziland local areas in Madagascar. In contrast, local areas in Liberia, coastal Ghana, eastern Gabon, parts of DRC and Angola, many parts of Namibia and Botswana, local areas in Zambia, southern Tanzania, northern Mozambique, and many parts of Madagascar has below-average rainfall.

Recent Rainfall Evolution Daily evolution of rainfall over the last 90 days at selected places reflects drier than normal condition over parts of Liberia (bottom panel-left). Moderate to locally heavy rainfall sustained rainfall surpluses over portions of western Ethiopia (top panel-right. Moderate to heavy rainfall helped to erode rainfall deficits over parts of South Sudan (bottom panel-right).

Atmospheric Circulation: Last 7 Days The 850 h. Pa wind anomaly (left panel) featured anomalous dry northeasterly flow across parts of West Africa, which may have contributed to the observed rainfall deficits in the region.

NCEP GEFS Model Forecasts Non-Bias Corrected Probability of precipitation exceedance Week-1: Valid May 29 – June 04, 2013 Week-2: Valid June 05 – June 11, 2013 For week-1 (left panel) there is an increased chance for rainfall to exceed 50 mm across Gulf of Guinea coast, and local areas in central Africa and western Ethiopia. The probability of exceedance is likely to decrease during week-2 (right panel).

Experimental Week-1 Precipitation Outlooks May 29 – June 4, 2013 1. There is an increased chance for above-average rainfall over Guinea-Bissau, Guinea Conakry and parts of Liberia: Anomalous lower-level cyclonic vortex and easterly wave propagating across the Gulf of Guinea countries is likely to enhance rainfall in the region. Confidence: Moderate 2. There is an increased chance for below-average rainfall across portions of southern Mali and Burkina Faso: Anomalous lower-level anti-cyclonic flow, with its associated divergence is expected to suppress rainfall in the region. Confidence: Moderate

Experimental Week-2 Precipitation Outlooks June 5 – June 11, 2013 1. There is an increased chance for above-average rainfall over eastern Burkina Faso, northern Togo, northern Benin, northern Nigeria and portions of Chad: Stronger than normal lower-level wind convergence is expected to enhance rainfall in the region. Confidence: Moderate 2. There is an increased chance for below-average rainfall over much of CAR: Anomalous lower-level divergence is expected to suppress rainfall. Confidence: Moderate 3. There is an increased chance for above-average rainfall over western Kenya: Stronger than normal lower-level wind convergence is expected to enhance rainfall in the region. Confidence: Moderate

Summary • During the past seven days, rainfall was above-average over portions of Guinea, Sierra Leone, Cote D’Ivoire, western Burkina Faso, southern Benin, southern Nigeria, local areas in Cameroon, southern Chad, portions of South Sudan, and western Ethiopia. In contrast, much of Liberia, local areas in Mali, parts of Ghana and Burkina Faso, Nigeria, Cameroon, much of Gabon, Congo, CAR, portions of DRC, much of Uganda, eastern South Sudan, and local areas in Kenya and Ethiopia had below-average rainfall. • During the past 30 days, below-average rainfall was observed over western Liberia, parts of Mali, local areas in Guinea, southern Ghana, Burkina Faso, much of Nigeria, portions of Cameroon, local area in Congo and DRC, northern Tanzania, portions of Kenya, and southern Ethiopia. In contrast, local areas in Guinea, Cote D’Ivoire, Benin, northern Cameroon, parts of Gabon and Congo, CAR, portions of DRC, South Sudan, western Ethiopia, and local areas in Kenya, Tanzania and southern Somalia received above-average rainfall. • During the past 90 days, parts of Cote D’Ivoire, Togo and Benin, western Gabon, much of CAR, parts of Angola and DRC, Ethiopia, western Kenya, southern Somalia, and local areas in Madagascar received above-average rainfall. In contrast, rainfall was below-average over parts of Nigeria, southern and eastern Angola, portions of Zambia and Namibia, Botswana, southern Tanzania, northern Mozambique and many parts of Madagascar. Week-1 outlooks call for an increased chance for above-average rainfall over Guinea-Bissau, Guinea Conakry and parts of Liberia. In contrast, there is an increased chance for below-average rainfall across portions of southern Mali and Burkina Faso. •