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 August 2015 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 total rainfall exceeded 150mm over western Guinea Sierra Leone. Heavy rainfall was also observed over local areas in eastern Senegal, Guinea-Bissau, southwestern Mali, eastern Sudan and northwestern Ethiopia. • Week-1 outlooks call for an increased chance for above-average rainfall over much of Senegal, Guinea, Guinea-Bissau, Sierra Leone, Gambia, southern and central Mali, Burkina Faso, portions of northern Cote d'Ivoire, northern Ghana, northern Togo, western Ethiopia and the neighboring areas of eastern Sudan and southern Eritrea.

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

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

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

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

8. Recent Rainfall Evolution Daily evolution of rainfall over the last 90 days at selected places reflects that moderate to heavy rainfall sustained moisture surpluses over portions of eastern Senegal (bottom left), and helped to offset accumulated rainfall deficits over parts of southern Niger (bottom right). In contrast, seasonal total rainfall remained below-average over portions of northeastern Ethiopia (top right).

9. Atmospheric Circulation:Last 7 Days The 850hpa wind anomalies (left panel) featured westerlies across the Sahel region, and anomalous lower-level easterlies along the Gulf of Guinea coast, resulting in lower-level cyclonic shear across Guinea and the neighboring areas. This anomalous lower-level cyclonic shear, combined with anomalous upper-level divergent flow (right panel) may have contributed to the observed heavy rainfall in the region.

10. NCEP GEFS Model ForecastsNon-Bias Corrected Probability of precipitation exceedance Week-1: Valid 18 – 24 Aug 2015Week-2: Valid 25 – 31 Aug 2015 For week-1 (left panel) and week-2(right panel), there is an increased chance for rainfall to exceed 50 mm over portions of Senegal, Gambia, Guinea-Bissau, Guinea-Conakry, Sierra Leone, northern Cote d’Ivoire, southern Mali, Burkina Faso, northern Ghana, northern Togo, Benin, Nigeria, Cameroon, southern Chad, western Sudan and western Ethiopia.

11. Week-1 Precipitation Outlooks 18 – 24 August, 2015 • There is an increased chance for above-average rainfall over much of Senegal, Guinea, Guinea-Bissau, Sierra Leone, Gambia, southern and central Mali, Burkina Faso, portions of northern Cote d'Ivoire, northern Ghana and northern 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 western Ethiopia and the neighboring areas of eastern Sudan and southern Eritrea: 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 portions of South Sudan, Uganda and northeastern Democratic Republic of the Congo: Anomalous lower-level divergence and upper-level convergence is expected to suppress rainfall in the region. Confidence: Moderate

12. Week-2 Precipitation Outlooks 25 – 31 August, 2015 • There is an increased chance for above-average rainfall over southern Niger, portions of northern Nigeria, Chad and western Sudan: A broad area of anomalous lower-level convergence is expected to enhance is expected to enhance rainfall in the region. Confidence: Moderate • There is an increased chance for below-average rainfall over much of South Sudan Republic, portions of southern Sudan, northeastern DRC and western Uganda: Anomalous lower-level divergence coupled with anomalous upper-level convergence is expected to enhance rainfall in the region. Confidence: Moderate

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