The African Monsoon Recent Evolution and Current Status Include Week-1 and Week-2 Outlooks

1. The African Monsoon Recent Evolution and Current StatusInclude Week-1 and Week-2 Outlooks Update prepared by Climate Prediction Center / NCEP 21 August 2017 For more information, visit: http://www.cpc.ncep.noaa.gov/products/Global_Monsoons/African_Monsoons/precip_monitoring.shtml

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

3. Highlights:Last 7 Days • Below-average rainfall was observed over many places in West Africa. • Rainfall was above-average over portions of DRC, Sudan, northern Ethiopia and Eritrea. • Week-1 outlooks call for an increased chance for above-average rainfall over southern Mauritania, Senegal, Gambia, Guinea-Bissau, portions of Mali and Burkina Faso, western Niger, and eastern Sudan, South Sudan Republic, western Ethiopia and Eritrea.

4. Rainfall Patterns: Last 7 Days During the past seven days, above-average rainfall was observed over much of Senegal, southern Mauritania, parts of Guinea, Sierra Leone, Togo, Benin, parts of Niger and Chad, local areas in CAR, parts of DRC, Sudan, portions of South Sudan, Eritrea, and northern Ethiopia. In contrast, rainfall was below-average over portions of Mali, eastern Guinea, Liberia, Burkina Faso, Ghana, western Niger, Nigeria, Cameroon, local areas in South Sudan and Uganda, and southwestern Ethiopia.

5. Rainfall Patterns: Last 30 Days During the past 30 days, rainfall was above-average over much of Senegal, southern Mauritania, much of Mali, the Gambia, Guinea-Bissau, Guinea-Conakry, Sierra Leone, parts of Cote d’Ivoire, portions of Burkina Faso and Ghana, many parts of Niger, Togo, Benin, portions of Nigeria and Cameroon, parts of Congo-Brazzaville, local areas in southern Chad, CAR, parts of DRC and South Sudan, many parts of Sudan and Ethiopia, portions of Uganda and local areas in Kenya. In contrast, southwestern Mali, Liberia, southern Cote d’Ivoire, local areas in Burkina Faso, parts of Nigeria, local areas in Cameroon, portions of Chad, local areas in DRC, CAR and South Sudan had below-average rainfall.

6. Rainfall Patterns: Last 90 Days During the past 90 days, rainfall was above-average over southern Mauritania, Senegal, the Gambia, Guinea-Bissau, Guinea-Conakry, Sierra Leone, Liberia, Mali, Cote d’Ivoire, Ghana, Burkina Faso, western and central Niger, much of Togo, Benin, many parts of Nigeria, Cameroon, Congo-Brazzaville, much of CAR, southern Chad, northern and western DRC, southern and eastern Sudan, South Sudan Republic, many parts of Ethiopia, and local areas in Kenya and Somalia. In contrast, below-average rainfall was observed over local areas in Liberia and Cote d’Ivoire, portions of Nigeria, Equatorial Guinea, Gabon, central and eastern DRC, local areas in Ethiopia and Somalia, parts of Uganda, and coastal South Africa.

7. Rainfall Patterns: Last 180 Days During the past 180 days, rainfall was above-average over parts of Mauritania, Senegal, Gambia, Guinea-Bissau, many parts of Mali, Sierra Leone, Guinea-Conakry, parts of Liberia, Cote d’Ivoire, Burkina Faso, much of Ghana, Niger, Benin, portions of Nigeria, many parts of Cameroon, southern Chad, CAR, much of South Sudan, many parts of Ethiopia, southern and eastern Sudan, parts of Congo-Brazzaville, portions of southern Angola, portions of DRC, Namibia, Botswana, Zimbabwe, Malawi, much of Zambia, portions of South Africa, many parts of Mozambique and Tanzania, and Madagascar. In contrast, below-average rainfall was observed over local areas in Liberia, Cote d’Ivoire and Ghana, portions of Nigeria, Equatorial Guinea, Gabon, central Congo-Brazzaville, portions of DRC, much of Angola, parts of southern Ethiopia, Somalia, many parts of Kenya, local areas in Uganda and Tanzania, southern Namibia, southern Botswana, portions of South Africa, and local areas in Mozambique.

8. Recent Rainfall Evolution Daily evolution of rainfall over the last 90 days at selected locations shows that moderate to heavy rainfall sustained moisture surpluses over portions of Sierra Leone (bottom left) northwestern Ethiopia (top right). In contrast, seasonal total rainfall remained below-average over southeastern South Sudan (bottom right).

9. Atmospheric Circulation:Last 7 Days Anomalous lower-level dry northeasterly to easterly flow prevailed across portions of West Africa, whereas anomalous onshore flow was observed across Cameroon, Gabon, Congo-Brazzaville, extending into southern Chad and CAR.

10. NCEP GEFS Model ForecastsNon-Bias Corrected Probability of precipitation exceedance Week-1: Valid 22 – 28 August, 2017 Week-2: Valid 29 Aug – 04 Sep, 2017 For week-1 (left panel) and week-2 (right panel), there is an increased chance for weekly rainfall totals to exceed 50mm over many places in the Sahel and northern Gulf of Guinea countries, northern DRC, South Sudan, and western Ethiopia.

11. Week-1 Precipitation Outlooks 22 - 28 August 2017 • There is an increased chance for above-average rainfall over southern Mauritania, Senegal, Gambia, Guinea Bissau, portions of Mali and Burkina Faso, and western Niger: An area of anomalous lower-level convergence and upper-level divergence is expected to enhance rainfall in the region. Confidence: Moderate • There is an increased chance for above-average rainfall over, eastern Sudan, South Sudan Republic, western Ethiopia and Eritrea: An area of anomalous lower-level convergence coupled with upper-level divergence is expected to enhance rainfall. Confidence: Moderate

12. Week-2 Precipitation Outlooks 29 Aug - 4 Sep 2017 • There is an increased chance for below-average rainfall across southern Mauritania, Senegal, Gambia, Guinea-Bissau, northern Guinea, and western Mali: An area of anomalous lower-level divergence is expected to suppress rainfall in the region. Confidence: Moderate • There is an increased chance for above-average rainfall across southern Niger and northern Nigeria: An area of anomalous lower-level convergence is expected to enhance rainfall in the region. . Confidence: Moderate • There is an increased chance for above-average rainfall across southern Chad, southern Sudan, much of South Sudan Republic, and portions of Ethiopia: An area of anomalous lower-level convergence coupled with upper-level divergence is expected to enhance rainfall in the region. Confidence: Moderate

13. Summary • During the past 30 days, rainfall was above-average over much of Senegal, southern Mauritania, much of Mali, the Gambia, Guinea-Bissau, Guinea-Conakry, Sierra Leone, parts of Cote d’Ivoire, portions of Burkina Faso and Ghana, many parts of Niger, Togo, Benin, portions of Nigeria and Cameroon, parts of Congo-Brazzaville, local areas in southern Chad, CAR, parts of DRC and South Sudan, many parts of Sudan and Ethiopia, portions of Uganda and local areas in Kenya. In contrast, southwestern Mali, Liberia, southern Cote d’Ivoire, local areas in Burkina Faso, parts of Nigeria, local areas in Cameroon, portions of Chad, local areas in DRC, CAR and South Sudan had below-average rainfall. • During the past 30 days, rainfall was above-average over much of Senegal, southern Mauritania, much of Mali, the Gambia, Guinea-Bissau, Guinea-Conakry, Sierra Leone, parts of Cote d’Ivoire, portions of Burkina Faso and Ghana, many parts of Niger, Togo, Benin, portions of Nigeria and Cameroon, parts of Congo-Brazzaville, local areas in southern Chad, CAR, parts of DRC and South Sudan, many parts of Sudan and Ethiopia, portions of Uganda and local areas in Kenya. In contrast, southwestern Mali, Liberia, southern Cote d’Ivoire, local areas in Burkina Faso, parts of Nigeria, local areas in Cameroon, portions of Chad, local areas in DRC, CAR and South Sudan had below-average rainfall. • During the past 90 days, rainfall was above-average over southern Mauritania, Senegal, the Gambia, Guinea-Bissau, Guinea-Conakry, Sierra Leone, Liberia, Mali, Cote d’Ivoire, Ghana, Burkina Faso, western and central Niger, much of Togo, Benin, many parts of Nigeria, Cameroon, Congo-Brazzaville, much of CAR, southern Chad, northern and western DRC, southern and eastern Sudan, South Sudan Republic, many parts of Ethiopia, and local areas in Kenya and Somalia. In contrast, below-average rainfall was observed over local areas in Liberia and Cote d’Ivoire, portions of Nigeria, Equatorial Guinea, Gabon, central and eastern DRC, local areas in Ethiopia and Somalia, parts of Uganda, and coastal South Africa. • Week-1 outlooks call for an increased chance for above-average rainfall over southern Mauritania, Senegal, Gambia, Guinea-Bissau, portions of Mali and Burkina Faso, western Niger, and eastern Sudan, South Sudan Republic, western Ethiopia and Eritrea.