The African Monsoon Recent Evolution and Current Status Include Week-1 and Week-2 Outlooks Update prepared by Climate Prediction Center / NCEP 26 May 2015 For more information, visit:

Outline Highlights Recent Evolution and Current Conditions NCEP GEFS Forecasts Summary

Highlights: Last 7 Days Moderate to locally heavy rainfall resulted in moisture surpluses over Guinea, Sierra Leone, Liberia, Cote d’Ivoire, western Ghana, western Burkina Faso, northern DRC, portions of CAR and South Sudan Republic. Week-1 outlooks call for an increased chance for below-average rainfall across many places in the Gulf of Guinea countries. In contrast, there is an increased chance for above-average rainfall over many parts of Ethiopia, and portions of northern Somalia.

Rainfall Patterns: Last 7 Days During the past seven days, above-average rainfall was observed over much of Guinea- Conakry, Sierra Leone, Liberia, Cote d’Ivoire, western Burkina Faso, western Ghana, Central Africa, northern DRC, South Sudan Republic, and local areas in Ethiopia and southwestern Kenya. In contrast, parts of Nigeria, and local areas in DRC and Ethiopia had below-average rainfall.

Rainfall Patterns: Last 30 Days During the past 30 days, rainfall was above-average over much of Guinea and Sierra Leone, western Liberia, northern Cote d’Ivoire, local areas in Nigeria, southern Cameroon, Equatorial Guinea, much of Gabon, western CAR, portions of DRC, portions of Ethiopia, local areas in Somalia, Uganda, Kenya, and Tanzania. In contrast, Burkina Faso, southern Cote d’Ivoire, Ghana, Togo, Benin, much of Nigeria, northern Cameroon, eastern CAR, Congo-Brazzaville, northwestern Angola, portions of DRC, southern Ethiopia, and northeastern Kenya had below-average rainfall.

Rainfall Patterns: Last 90 Days During the past 90 days, rainfall was above-average over Guinea-Conakry, Sierra Leone, Cote d’Ivoire, southwestern Ghana, Benin, southern Nigeria, portions of Cameroon, Equatorial Guinea, much of Gabon, Congo-Brazzaville, central and southern CAR, South Sudan Republic, many parts of DRC, parts of Uganda and Ethiopia, Kenya, southern Somalia, many parts of Tanzania, Zambia, Botswana, Zimbabwe, central and northern Mozambique and many parts of Madagascar. In contrast, local areas in Liberia, Burkina Faso, Togo, northern Nigeria, northern Cameroon, local areas in southern Gabon, Angola, portions of Namibia and South Africa, southern Mozambique, Malawi, local areas in Tanzania, many parts of Ethiopia and local areas in Madagascar had below-average rainfall.

Rainfall Patterns: Last 180 Days During the past 180 days, rainfall was above-average over parts of Liberia, Cote d’Ivoire, southern Ghana, southern Nigeria, many parts of CAR, western Gabon, northern Congo- Brazzaville, portions DRC, southern Malawi, much of Mozambique, Botswana, Zimbabwe, and Madagascar. In contrast, portions of southeastern Mali, Burkina Faso, northern Ghana, northern Nigeria, portions of Cameroon, southern Gabon, southern Congo-Brazzaville, Angola, portions of DRC, Namibia, local areas in Zambia, portions of South Africa, Uganda, western Tanzania, eastern Kenya and many parts of Ethiopia had below-average rainfall.

Recent Rainfall Evolution Daily evolution of rainfall over the last 90 days at selected places reflects that moderate to heavy rainfall helped to offset rainfall deficits over portions of Sierra Leone (bottom left) and western Ethiopia (top right). In contrast, seasonal total rainfall continued to be below-average over parts of Nigeria (bottom right).

Atmospheric Circulation: Last 7 Days The 850hpa wind anomalies featured southeasterly flow with its associated convergence across western Equatorial Africa.

NCEP GEFS Model Forecasts Non-Bias Corrected Probability of precipitation exceedance Week-1: Valid 27 May – 02 June 2015 Week-2: Valid 03 June – 09 June 2015 For week-1 (left panel) and week-2 (right-panel), there is an increased chance for rainfall to exceed 50 mm along the Gulf of Guinea coast, and portions of the Greater Horn of Africa.

Week-1 Precipitation Outlooks 26 May – 02 June There is an increased chance for below-average rainfall across many places in the Gulf of Guinea countries: Anomalous lower-level dry northeasterly flow with its associated lower-level divergence is expected to suppress rainfall in the region. Confidence: Moderate 2.There is an increased chance for above-average rainfall over many parts of Ethiopia, and portions of northern Somalia: Anomalous lower-level southwesterly flow with its associated lower-level convergence is expected to enhance rainfall in the region. Confidence: Moderate

Week-2 Precipitation Outlooks June There is an increased chance for above-average rainfall over southern Cote d'Ivoire, much of Ghana, Togo, Benin, much of Nigeria, Cameroon, Equatorial Guinea, and Gabon: Anomalous lower-level southwesterly flow from the Atlantic Ocean with its associated lower-level convergence is expected to enhance rainfall in the region. Confidence: Moderate 2.There is an increased chance for below-average rainfall over northern DRC, and the neighboring places of CAR and South Sudan Republic: Anomalous lower-level wind divergence is expected to suppress rainfall in the region. Confidence: Moderate

Summary During the past seven days, above-average rainfall was observed over much of Guinea- Conakry, Sierra Leone, Liberia, Cote d’Ivoire, western Burkina Faso, western Ghana, Central Africa, northern DRC, South Sudan Republic, and local areas in Ethiopia and southwestern Kenya. In contrast, parts of Nigeria, and local areas in DRC and Ethiopia had below-average rainfall. During the past 30 days, rainfall was above-average over much of Guinea and Sierra Leone, western Liberia, northern Cote d’Ivoire, local areas in Nigeria, southern Cameroon, Equatorial Guinea, much of Gabon, western CAR, portions of DRC, portions of Ethiopia, local areas in Somalia, Uganda, Kenya, and Tanzania. In contrast, Burkina Faso, southern Cote d’Ivoire, Ghana, Togo, Benin, much of Nigeria, northern Cameroon, eastern CAR, Congo-Brazzaville, northwestern Angola, portions of DRC, southern Ethiopia, and northeastern Kenya had below- average rainfall. During the past 90 days, rainfall was above-average over Guinea-Conakry, Sierra Leone, Cote d’Ivoire, southwestern Ghana, Benin, southern Nigeria, portions of Cameroon, Equatorial Guinea, much of Gabon, Congo-Brazzaville, central and southern CAR, South Sudan Republic, many parts of DRC, parts of Uganda and Ethiopia, Kenya, southern Somalia, many parts of Tanzania, Zambia, Botswana, Zimbabwe, central and northern Mozambique and many parts of Madagascar. In contrast, local areas in Liberia, Burkina Faso, Togo, northern Nigeria, northern Cameroon, local areas in southern Gabon, Angola, portions of Namibia and South Africa, southern Mozambique, Malawi, local areas in Tanzania, many parts of Ethiopia and local areas in Madagascar had below-average rainfall. Week-1 outlooks call for an increased chance for below-average rainfall across many places in the Gulf of Guinea countries. In contrast, there is an increased chance for above-average rainfall over many parts of Ethiopia, and portions of northern Somalia.