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 04 September 2012 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 160mm across Southeast Nigeria, western Cameroon, southern Chad, and local areas in Guinea, Mali and Burkina Faso. • Week-1 outlooks call for an increased chance for above average rainfall over southern Senegal, Gambia, Guinea-Bissau, Guinea, Sierra Leone, portions of Liberia and Cote d’Ivoire, western Burkina Faso, southern Mali, CAR and the neighboring areas of Cameroon, Chad, Congo, DRC and South Sudan Republic. In contrast, below average rainfall is expected across northern Nigeria and the neighboring areas of Benin and Niger.

4. Rainfall Patterns: Last 7 Days During the past seven days, above average rainfall was observed over portions of Mali, Burkina Faso, Local areas in Guinea, northern Ghana, southern Niger, portions of Nigeria and Cameroon, southern Chad, portions of CAR, DRC, South Sudan Republic, eastern Sudan, portions of Ethiopia and Uganda. In contrast, portions of Senegal, southern Mauritania, many parts of Guinea, portions of Sierra Leone, Liberia, Cote D’Ivoire, western Burkina Faso, local areas in Mali, portions of Nigeria, Niger and Cameroon. Local areas in CAR and DRC, portions of Sudan and South Sudan, Eritrea and Northeast Ethiopia had below average rainfall.

5. Rainfall Patterns: Last 30 Days During the past 30 days, above-average rainfall was observed over southern Mauritania, much of Senegal, portions of Guinea Conakry, many parts of Mali, Burkina Faso, local areas in Cote d’Ivoire, portions of Niger and Nigeria, southern Chad, much of CAR, local areas in Sudan, South Sudan Republic, portions of DRC, local areas in Kenya and Uganda, and portions of Ethiopia. In contrast, many places in the Gulf of Guinea, Local areas in Senegal and CAR, portions of DRC and Sudan, Eritrea and Ethiopia received below average rainfall.

6. Rainfall Patterns: Last 90 Days During the past 90 days, rainfall was above average over portions of Senegal, much of Guinea Conakry, Guinea Bissau and Sierra Leone, portions of Mali, much of Burkina Faso, southern Niger, local areas in Nigeria and Cameroon, southern Chad, portions of CAR, South Sudan Republic, local areas in Sudan, Uganda and Kenya, and portions of Ethiopia. In contrast, portions of Liberia, coastal Cote d’Ivoire, portions of Nigeria, Cameroon, Equatorial Guinea, northern Gabon, portions of Congo, and local areas in DRC and Ethiopia had below average rainfall.

7. Rainfall Patterns: Last 180 Days During the past 180 days, rainfall was above-average over portions of Guinea Conakry and much of Sierra Leone, portions of Senegal, southern Mauritania, Mali, local areas in Ghana, Togo and Benin, portions of northern Nigeria, southern Chad, local areas in CAR and Gabon, western Kenya, South Sudan, portions of Madagascar, Somalia and local areas in Ethiopia. In contrast, moisture deficits were observed over parts of Liberia, coastal Cote d’Ivoire, portions of Nigeria, much ofCameroon, portions of Congo and Ethiopia.

8. Recent Rainfall Evolution Daily evolution of rainfall over the last 90 days at selected stations reflects that the recent heavy rains helped to offset some of the the rainfall deficits over Southeast Nigeria (bottom panel – left). Seasonal total rainfall remained above-average across portions of Nigeria (bottom panel – right). Moderate to heavy rains sustained rainfall surpluses across portions of Ethiopia (top panel – right).

9. Atmospheric Circulation:Last 5 Days The 850hPa wind anomaly (left panel) featured anomalous lower level westerlies across the Gulf of Guinea region. The 200hpa wind anomaly (right panel) featured anomalous anticyclonic flow across Southeastern Africa.

10. NCEP GEFS Model ForecastsNon-Bias Corrected Probability of precipitation exceedance Week-1: Valid 05 – 11 September 2012Week-2: Valid 12 – 18 September 2012 For week-1 (left panel) and week-2 (right panel), there is an increased chance for rainfall to exceed 50 mm over many places of the Gulf of Guinea and Central African countries, and across portions of South Sudan and western Ethiopia.

11. Experimental Week-1 Precipitation Outlooks Week-1 Outlook 05 – 11 September 2012 • There is an increased chance for above-average rainfall over southern Senegal, Gambia, Guinea-Bissau, Guinea, Sierra Leone, portions of Liberia and Cote d’Ivoire, western Burkina Faso and southern Mali: Anomalous westerlies from the Atlantic Ocean and their associated convergence are expected to enhance rainfall in the region. Confidence: Moderate • There is an increased chance for below-average rainfall over northern Nigeria and the neighboring areas of Benin and Niger: Anomalous lower level divergence is expected to suppress rainfall in the region. Confidence: Moderate • There is an increased chance for above-average rainfall over CAR and the neighboring areas of Cameroon, Chad, Congo, DRC and South Sudan Republic: Anomalous southwesterly winds from the Atlantic Ocean and their associated convergence across portions of Central Africa are expected to enhance rainfall in the region. Confidence: Moderate

12. Experimental Week-2 Precipitation Outlooks Week-2 Outlook 12 – 18 September 2012 • There is an increased chance for above-average rainfall across portions of the Central African countries: Anomalous southwesterly winds from the Atlantic Ocean, with their associated convergence are expected to enhance rainfall in the region. Confidence: Moderate

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