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 10 September 2018 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 • Weekly rainfall surpluses exceeded 100mm over parts of Southern Senegal, Guinea-Bissau, Guinea Conakry, Sierra Leone, local areas in Cote d’Ivoire and portions of Nigeria. • Week-1 outlooks call for an increased chance for above-average rainfall over much of West Africa. Outlooks also call for above-average rainfall over southern Chad and northern CAR, eastern Sudan, Eritrea and western Ethiopia. In contrast, there is an increased chance for below-average rainfall across parts of Uganda and South Sudan.

4. Rainfall Patterns: Last 7 Days During the past 7 days, weekly rainfall totals exceeded 100mm over southern Senegal, Guinea-Bissau, many parts of Guinea-Conakry, Sierra Leone, parts of southern Mali and Liberia, western Cote d’Ivoire, parts of Burkina Faso, eastern Ghana, northern Togo, parts of Nigeria, western Cameroon, eastern Sudan, western Eritrea and parts of Ethiopia. Above-average rainfall was observed over southern Mauritania, much of Senegal, The Gambia, Guinea-Bissau, Guinea-Conakry, Mali, Sierra Leone, Liberia, Cote d’Ivoire, portions of Burkina Faso, Ghana, Togo, Benin, parts of Niger and Nigeria, parts of Cameroon, Chad, local areas in CAR, Congo-Brazzaville and DRC, many parts of Sudan, South Sudan, Eritrea, northern Ethiopia, local areas in Uganda, parts of Angola, and southern South Africa. In contrast, below-average rainfall was observed over local areas in Burkina Faso, Nigeria and Cameroon, parts of CAR and DRC, southeastern South Sudan, and parts of southern Ethiopia.

5. Rainfall Patterns: Last 30 Days During the past 30 days, rainfall was above-average over southern Mauritania, much of Senegal, Mali, Guinea-Conakry, Sierra Leone, Liberia, Cote d’Ivoire, Burkina Faso, Ghana, Togo, Benin, western Niger, portions of Nigeria, much of Cameroon, Chad, Congo-Brazzaville, portions of Central African Republic, portions of DRC, northern Angola, many parts of Sudan, South Sudan, Eritrea, much of Ethiopia, and southern South Africa. Below-average rainfall was observed over local areas in Niger, portions of Nigeria, local areas in Central African Republic, Equatorial Guinea. Below-average rainfall was also observed over portions DRC, parts of Uganda, and local areas in southwestern Ethiopia.

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

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

8. Recent Rainfall Evolution Daily evolution of rainfall over the last 90 days at selected locations shows that moderate to locally heavy rainfall sustained moisture surpluses over eastern Guinea-Conakry (bottom left) and eastern Sudan (top right). In contrast, seasonal total rainfall remained below-average over northeastern DRC (bottom right).

9. Atmospheric Circulation:Last 7 Days A broad area of anomalous strong westerly flow with its associated cyclonic shear prevailed over West and Central Africa.

10. NCEP GEFS Model ForecastsNon-Bias Corrected Probability of precipitation exceedance Week-1: 11 – 17 September, 2018 Week-2: Valid 18 – 24 September, 2018 For week-1 (left panel), there is an increased chance for weekly rainfall totals to exceed 50 mm over many places in the Gulf of Guinea countries and the neighboring areas of the Sahel region, northeastern DRC and western Ethiopia. For week-2 (left panel), there is an increased chance for weekly rainfall totals to exceed 50 mm over portions of the Gulf of Guinea countries, northeastern DRC and parts of western Ethiopia.

11. Week-1 Precipitation Outlooks 11 – 17 September, 2018 • There is an increased chance for above-average rainfall over parts of southern Mauritania, Senegal, Guinea-Bissau,Guinea-Conakry, Sierra Leone, Liberia, Mali, Burkina Faso, Cote d'Ivoire, Ghana, Togo, Benin, Niger and Nigeria: A broad 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 across parts of southern Chad, Northern CAR, and southwestern Sudan: 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 below-average rainfall across parts of South Sudan and Uganda: An area of anomalous lower-level divergence and upper-level convergence is expected to suppress rainfall in the region. Confidence: Moderate • There is an increased chance for above-average rainfall over parts of eastern Sudan, western Eritrea, and Ethiopia: An area of anomalous lower-level convergence and upper-level divergence is expected to enhance rainfall in the region. Confidence: Moderate

12. Week-2 Precipitation Outlooks 18 – 24 September, 2018 • There is an increased chance for above-average rainfall across parts of Senegal, Guinea-Conakry, Sierra Leone, Liberia, Mali, Burkina Faso, Cote d'Ivoire, Ghana, Togo, Benin, Nigeria, and Cameroon: A broad area 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 across parts of Southern Sudan: 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 below-average rainfall across parts of Southwestern DRC and northern Angola: An area of anomalous upper-level convergence is expected to suppress rainfall in the region. Confidence: Moderate

13. Summary • During the past 7 days, weekly rainfall totals exceeded 100mm over southern Senegal, Guinea-Bissau, many parts of Guinea-Conakry, Sierra Leone, parts of southern Mali and Liberia, western Cote d’Ivoire, parts of Burkina Faso, eastern Ghana, northern Togo, parts of Nigeria, western Cameroon, eastern Sudan, western Eritrea and parts of Ethiopia. Above-average rainfall was observed over southern Mauritania, much of Senegal, The Gambia, Guinea-Bissau, Guinea-Conakry, Mali, Sierra Leone, Liberia, Cote d’Ivoire, portions of Burkina Faso, Ghana, Togo, Benin, parts of Niger and Nigeria, parts of Cameroon, Chad, local areas in CAR, Congo-Brazzaville and DRC, many parts of Sudan, South Sudan, Eritrea, northern Ethiopia, local areas in Uganda, parts of Angola, and southern South Africa. In contrast, below-average rainfall was observed over local areas in Burkina Faso, Nigeria and Cameroon, parts of CAR and DRC, southeastern South Sudan, and parts of southern Ethiopia. • During the past 30 days, rainfall was above-average over southern Mauritania, much of Senegal, Mali, Guinea-Conakry, Sierra Leone, Liberia, Cote d’Ivoire, Burkina Faso, Ghana, Togo, Benin, western Niger, portions of Nigeria, much of Cameroon, Chad, Congo-Brazzaville, portions of Central African Republic, portions of DRC, northern Angola, many parts of Sudan, South Sudan, Eritrea, much of Ethiopia, and southern South Africa. Below-average rainfall was observed over local areas in Niger, portions of Nigeria, local areas in Central African Republic, Equatorial Guinea. Below-average rainfall was also observed over portions DRC, parts of Uganda, and local areas in southwestern Ethiopia. • During the past 90 days, much of Senegal, The Gambia, southern Mauritania, much of Mali and Guinea-Conakry, Guinea-Bissau, Sierra Leone, Liberia, Côte d’Ivoire, Burkina Faso, Ghana, Togo, Benin, Niger, portions of Nigeria, Chad, many parts of Cameroon, portions of Central African Republic, Congo-Brazzaville, western DRC, Sudan, parts of South Sudan, portions of Ethiopia, southwestern Kenya and local areas in Angola received above-average rainfall. Rainfall was below-average over parts of Nigeria, local areas in Cameroon, Equatorial Guinea, parts of Gabon, southern Congo-Brazzaville, local areas in CAR, central and eastern DRC, southeastern South Sudan, and parts of Ethiopia and Uganda. • Week-1 outlooks call for an increased chance for above-average rainfall over much of West Africa. Outlooks also call for above-average rainfall over southern Chad and northern CAR, eastern Sudan, Eritrea and western Ethiopia. In contrast, there is an increased chance for below-average rainfall across parts of Uganda and South Sudan.