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 13 August 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 western Guinea-Conakry, and parts of Sierra Leone and Mali. • Week-1 outlooks call for an increased chance for above-average rainfall over parts of Senegal, Guinea-Conakry, Sierra Leone, Mali, Burkina Faso, Cote d'Ivoire, Ghana, Togo, Benin, Nigeria, Niger, and parts of eastern Chad, northern CAR, northern South Sudan and Sudan. In contrast, there is an increased chance for below-average rainfall over parts of CAR, northern Congo, northern DRC and South Sudan.

4. Rainfall Patterns: Last 7 Days During the past 7 days, weekly rainfall totals exceeded 100mm in western Guinea-Conakry, Sierra Leone and parts of Mali and Burkina Faso. Above-average rainfall was observed over much of Guinea-Conakry and Mali, Sierra Leone, Burkina Faso, Niger, portions of Nigeria, Mali, Chad, Cameroon, portions of Sudan and northern Ethiopia. Below average rainfall was observed western and central Senegal, local areas in Sierra Leone, parts of Cote d’Ivoire and Ghana, portions of Nigeria, parts of southern Chad, CAR, parts of DRC and South Sudan, Local areas in Sudan and portions of Ethiopia.

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

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

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

8. Recent Rainfall Evolution Daily evolution of rainfall over the last 90 days at selected locations shows that little or no rainfall was observed along coastal Senegal (bottom left) and parts of southwestern Ethiopia (bottom right) over the past several weeks. In contrast, moderate to locally heavy rainfall continued to sustain moisture surpluses over portions of Sudan (top right).

9. Atmospheric Circulation:Last 7 Days An area of anomalous cyclonic circulation in portions of West Africa, and anomalous lower-level convergence in Sudan may have contributed to the observed rainfall surpluses in the regions.

10. NCEP GEFS Model ForecastsNon-Bias Corrected Probability of precipitation exceedance Week-1: Valid 14 – 20 August, 2018 Week-2: Valid 21 – 27 August, 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 many places in the Sahel region, and parts of Sudan, northeastern DRC, western Kenya, parts of Eritrea and Ethiopia.

11. Week-1 Precipitation Outlooks 14 – 20 August, 2018 • There is an increased chance for above-average rainfall over parts of Senegal, Guinea, Sierra Leone, Mali, Burkina Faso, Cote d'Ivoire, Ghana, Togo, Benin, Nigeria, and Niger: 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 CAR, northern Congo, northern DRC and South Sudan: An area of 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 Chad, northern CAR, northern South Sudan and Sudan: 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 21 – 27 August, 2018 • There is an increased chance for above-average rainfall across parts of Mali, Burkina Faso, northern Benin, Niger, Nigeria, northern Cameroon, Chad and western Sudan: 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 over parts of northern DRC, Rwanda, Uganda, South Sudan, southern Ethiopia and Kenya: An area of anomalous upper-level divergence is expected to enhance rainfall in the region. Confidence: Moderate

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