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 09 September 2013 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 • Moderate to locally heavy rainfall sustained moisture surpluses over the western end of West Africa. • Below-average rainfall prevailed over northern Ghana, Togo, Benin Nigeria, and portions of the central African countries. • Week-1 outlooks call for an increased chance for above-average rainfall over many places in the Gulf of Guinea region. In contrast, there is an increased chance for below-average rainfall over southeastern South Sudan Republic.

4. Rainfall Patterns: Last 7 Days During the past seven days, above-average rainfall was observed over much of Senegal, Guinea, Sierra Leone, portions of Mali, local areas in Burkina Faso and northern Cote d’Ivoire, southeastern Nigeria, many parts of Cameroon, local areas in CAR, central and southern Congo, southwestern DRC, southeastern Sudan, local areas in the Lake Victoria region and parts of Ethiopia. In contrast, local areas in Cote d’Ivoire, many places in Ghana, Togo, Benin and Nigeria, southern Chad, CAR, northern Congo, and portions of DRC had below average rainfall.

5. Rainfall Patterns: Last 30 Days During the past 30 days, rainfall was below-average over Liberia, Cote d’Ivoire, Ghana, much of Togo and Benin, many parts of Nigeria, western and central Cameroon, Equatorial Guinea, northern Gabon, local areas in CAR and Sudan, portions of South Sudan and DRC. In contrast, much of Senegal, Guinea, Sierra Leone, Mali, Burkina Faso, portions of Niger, eastern Cameroon, western CAR, central Sudan, local areas in South Sudan and DRC, many parts of Ethiopia, and local areas in the Lake Victoria region received below-average rainfall.

6. Rainfall Patterns: Last 90 Days During the past 90 days, Guinea, Sierra Leone, portions of Mali, local areas in Burkina Faso, western Niger, local areas in southern Chad, CAR and northwestern DRC, and portions of Ethiopia received above-average rainfall. In contrast, rainfall was below-average over Liberia, Cote D’Ivoire, Ghana, Togo, Benin, Nigeria, Equatorial Guinea, northern Gabon, central Congo, local areas in DRC, eastern Sudan, northwestern Ethiopia and Eritrea.

7. Rainfall Patterns: Last 180 Days During the past 180 days, rainfall was above-average over much of Guinea, Sierra Leone, portions of Mali, Burkina Faso, western Niger, much of CAR, local areas in DRC and South Sudan, many parts of Ethiopia, western Kenya, southern Somalia, and local areas in northern Angola. In contrast, parts of Liberia, Ghana, Nigeria, southern Cameroon, Equatorial Guinea, northern Gabon, central Congo, local areas in eastern DRC, southeastern Angola and western Zambia, southern Tanzania, northern Mozambique, and northern Madagascar 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 Guinea (bottom panel-left). Seasonal total rainfall remained below-average, despite frequent rainfall observation over portions of Nigeria(bottom panel right) , and Sudan (top panel-right).

9. Atmospheric Circulation:Last 7 Days The 850hPa wind anomaly (left panel) featured anomalous easterly to northeasterly flow across northern Indian Ocean and the Greater Horn of Africa.

10. NCEP GEFS Model ForecastsNon-Bias Corrected Probability of precipitation exceedance Week-1: Valid September 10 – September 16, 2013Week-2: Valid September 17 – September 23, 2013 For week-1 (left panel) and week-2 (right panel), there is an increased chance for rainfall to exceed 50 mm over many places in the Gulf of Guinea countries, parts of central African region, and western Ethiopia.

11. Experimental Week-1 Precipitation Outlooks Sept 10 – Sept 16, 2013 • There is an increased chance for above-average rainfall over many places in the Gulf of Guinea region: Anomalous lower-lever convergence associated with the West African monsoon flow is expected to enhance rainfall in the region. Confidence: Moderate • There is an increased chance for below-average rainfall over southeastern South Sudan: Anomalous lower-level divergence is expected to suppress rainfall in the region. Confidence: Moderate

12. Experimental Week-2 Precipitation Outlooks Sept 17 – Sept 23, 2013 • There is an increased chance for below-average rainfall over eastern Liberia, Cote d’Ivoire, Ghana, Togo, Benin, and western Nigeria: Anomalous lower-level off-shore flow with its associated divergence is expected to suppress rainfall in the region. Confidence: Moderate

13. Summary During the past seven days, above-average rainfall was observed over much of Senegal, Guinea, Sierra Leone, portions of Mali, local areas in Burkina Faso and northern Cote d’Ivoire, southeastern Nigeria, many parts of Cameroon, local areas in CAR, central and southern Congo, southwestern DRC, southeastern Sudan, local areas in the Lake Victoria region and parts of Ethiopia. In contrast, local areas in Cote d’Ivoire, many places in Ghana, Togo, Benin and Nigeria, southern Chad, CAR, northern Congo, and portions of DRC had below average rainfall. During the past 30 days, rainfall was below-average over Liberia, Cote d’Ivoire, Ghana, much of Togo and Benin, many parts of Nigeria, western and central Cameroon, Equatorial Guinea, northern Gabon, local areas in CAR and Sudan, portions of South Sudan and DRC. In contrast, much of Senegal, Guinea, Sierra Leone, Mali, Burkina Faso, portions of Niger, eastern Cameroon, western CAR, central Sudan, local areas in South Sudan and DRC, many parts of Ethiopia, and local areas in the Lake Victoria region received below-average rainfall. During the past 90 days, Guinea, Sierra Leone, portions of Mali, local areas in Burkina Faso, western Niger, local areas in southern Chad, CAR and northwestern DRC, and portions of Ethiopia received above-average rainfall. In contrast, rainfall was below-average over Liberia, Cote D’Ivoire, Ghana, Togo, Benin, Nigeria, Equatorial Guinea, northern Gabon, central Congo, local areas in DRC, eastern Sudan, northwestern Ethiopia and Eritrea. Moderate to locally heavy rainfall sustained moisture surpluses across the western end of West Africa. Week-1 outlooks call for an increased chance for above-average rainfall over many places in the Gulf of Guinea region. In contrast, there is an increased chance for below-average rainfall over southeastern South Sudan Republic.