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 17 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 totals exceeded 100mm over eastern Guinea-Conakry, Sierra Leone, parts of Liberia and Cote d’Ivoire, and local area in Gabon. • Below-average rainfall was observed across western Senegal and Guinea-Bissau, many parts of Nigeria, Cameroon, southern CAR and parts of South Sudan. • Week-1 outlooks call for an increased chance for above-average rainfall over much of Guinea-Conakry, Sierra Leone, Liberia, Cote d'Ivoire, Ghana, and Togo. In contrast there is an increased chance for below-average rainfall across northern Angola and southwestern DRC, and northern Uganda and southern South Sudan.

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

5. Rainfall Patterns: Last 30 Days During the past 30 days, rainfall was above-average over southern Mauritania, Senegal, The Gambia, Guinea-Bissau, Mali, Guinea-Conakry, Sierra Leone, Liberia, Cote d’Ivoire, Burkina Faso, Ghana, Togo, Benin, western and southern Niger, portions of Nigeria, many parts of Cameroon, Chad, Gabon, Congo-Brazzaville, portions of Central African Republic, and DRC, northern Angola, many parts of Sudan, South Sudan, Eritrea, many parts of Ethiopia, and southern South Africa and southern Madagascar. Below-average rainfall was observed over portions of Nigeria and Cameroon, Equatorial Guinea, eastern Central African Republic, Below-average rainfall was also observed over portions DRC, and local areas in western Kenya and 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 northern Angola received above-average rainfall. Above-average rainfall was also observed along coastal South Africa, and local areas in Mozambique and Madagascar. Rainfall was below-average over parts of Nigeria, local areas in Cameroon, Equatorial Guinea, 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 western Madagascar. Below-average rainfall was observed over parts of Nigeria, western Cameroon, much of Gabon, local areas in Congo-Brazzaville, portions of DRC , northwestern Angola, local areas in Ethiopia, local areas in of Botswana and Zimbabwe, and eastern 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 northern Ethiopia (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 southwesterly 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: 18 – 24 September, 2018 Week-2: Valid 25 Sep – 1 Oct, 2018 For week-1 (left panel) and week-2 (right 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 Ethiopia.

11. Week-1 Precipitation Outlooks 18 – 24 September • There is an increased chance for above-average rainfall over much of Guinea-Conakry, Sierra Leone, Liberia, Cote d'Ivoire, Ghana, and Togo: 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 below-average rainfall across parts of northern Angola and Southern DRC: 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 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

12. Week-2 Precipitation Outlooks 25 Sep – 1 Oct, 2018 • There is an increased chance for above-average rainfall across much of Guinea-Conakry, Guinea-Bissau, Sierra Leone, Liberia, Cote D'Ivoire, Ghana, and Togo: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 Sudan, South Sudan, and Uganda: 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 Southern DRC and northern Angola: An area of anomalous lower-level divergence and below normal Atlantic SSTs are expected to suppress rainfall in the region. Confidence: Moderate

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