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 05 December 2011 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 • Another week of heavy rainfall sustained moisture surpluses across southern Ethiopia, Kenya and eastern Uganda. • Rainfall continued to be suppressed across northern DRC, Congo and portions of Gabon. • Week-1 outlooks call for an increased chance for above average rainfall over southern Angola, northern Namibia western Botswana, northern Zambia, eastern DRC, eastern Uganda, much of Tanzania, southern Kenya, Malawi and northern Mozambique, while rainfall deficits are expected across portions of central and southeastern African countries.

4. Rainfall Patterns: Last 7 Days During the past seven days, below average rainfall was observed over local areas across the Gulf of Guinea coast, portions of southern Cameroon, much of Gabon, Congo, northern DRC, western Angola, central and eastern Zambia, central Tanzania, northern and southern Zimbabwe, Malawi, northern and southern Mozambique, southern and eastern Botswana, northeastern South Africa, Swaziland, and southern and western Madagascar. In contrast, moisture surpluses were observed across southern Ethiopia, much of Kenya, southern Somalia, parts of Uganda, western and southeastern Tanzania, central and southern Angola, local areas in Namibia, southern South Africa and northern Madagascar.

5. Rainfall Patterns: Last 30 Days During the past 30 days, above average rainfall was observed across eastern Guinea, coastal Cote D’Ivoire, local areas in southern Nigeria, southern and northern ends of Congo, western and southern DRC, much of Angola, northern Zambia, Uganda, portions of Tanzania, much of Kenya, southern Ethiopia, southern and central Somalia, northern Botswana, eastern Zimbabwe, southern Mozambique and parts of northern Madagascar. In contrast, eastern Liberia, portions of Cote D’Ivoire, southern Nigeria, many parts of Cameroon, Gabon, Equatorial Guinea, central Congo, CAR, central and northern DRC, parts of South Sudan Republic, southwest Ethiopia, eastern and central Namibia, southwestern Botswana, many places of South Africa, Lesotho, Swaziland and much of Madagascar had below average rainfall.

6. Rainfall Patterns: Last 90 Days During the past 90 days, moisture deficits were observed across southern Mauritania, Senegal, western Mali, portions of Burkina Faso, coastal Guinea, local areas in Nigeria, southern Cameroon, northern Gabon, central Sudan, western and eastern Ethiopia, parts of Namibia, southwestern Botswana, South Africa, Lesotho, parts of Mozambique and Madagascar. In contrast, central Mali, coastal Cote D’Ivoire, southern Ghana, Togo, southern Benin, local areas in Cameroon, Gabon, Congo, CAR, DRC, Uganda, northern Tanzania, much of Kenya, central and southern Somalia, southern Ethiopia, and southern South Sudan Republic received above average rainfall.

7. Rainfall Patterns: Last 180 Days During the past 180 days, rainfall was above average across northern Guinea, central Mali, Ghana, Togo, southern Benin, local areas in Chad, coastal Gabon, parts of Congo, northern CAR, portions of DRC, southern South Sudan Republic, Uganda, much of Kenya, southern Ethiopia, central and southern Somalia, northern Tanzania and northern Angola. Moisture deficits were observed across southern Mauritania, southern Senegal, coastal Guinea Conakry, Sierra Leone, Liberia, western Cote D’Ivoire, local areas in western Burkina Faso, western Niger much of Nigeria, portions of Cameroon, northern Gabon, eastern Sudan, Eritrea, Ethiopia with developing moisture deficits in southern Botswana, Lesotho, central areas in South Africa and southern Madagascar.

8. Recent Rainfall Evolution Daily evolution of rainfall over the last 90 days at selected stations reflects the recent decrease in rainfall across northern DRC (bottom panel-left). Rainfall continued to be suppressed over many parts of South Africa (bottom panel – right). In contrast, an other week of heavy rains sustained moisture surpluses across Kenya (top panel – right).

9. Atmospheric Circulation:Last 7 Days The 850hPa wind anomaly (left panel) featured anomalous convergence between northerly and southwesterly winds across East Africa and anomalous cyclonic flow near Angola and Namibia, which may have contributed to the above average rainfall in the regions. The 200hPa wind anomaly (right panel) featured a stronger than normal Subtropical Westerly Jet across northern Africa.

10. NCEP GEFS Model ForecastsNon-Bias Corrected Probability of precipitation exceedance Week-1: Valid 06 – 12 December 2011Week-2: Valid 13 – 19 December 2011 For week-1 (left panel) there is an increased chance for rainfall to exceed 50 mm over southern Gabon, southern Congo, southern and central DRC, Angola, northern Namibia, Zambia, Rwanda, Burundi, Tanzania, northern Mozambique, northern Madagascar and local areas in South Africa. For week-2 (right panel), higher chances for heavy rainfall are expected to extend towards Zimbabwe and southern Mozambique.

11. Experimental Week-1 Precipitation Outlooks • There is an increased chance for below average rainfall over Gabon, Congo and portions of DRC: The combination of anomalous lower tropospheric divergence across central Africa and the projected phase of the MJO are expected to suppress rainfall in the region. Confidence: Moderate • There is an increased chance for above average rainfall over southern Angola, northern Namibia and western Botswana: Anomalous westerlies from the Atlantic Ocean are expected to enhance rainfall in the region.. Confidence: Moderate • There is an increased chance for above average rainfall over eastern DRC, Rwanda, Burundi, northern Zambia, Malawi, northern Mozambique, much of Tanzania and southern Kenya: The combination of anomalous lower tropospheric convergence across East Africa and the projected phase of the MJO are expected to enhance rainfall in the region. Confidence: Moderate • There is an increased chance for below average rainfall over eastern Zimbabwe, northeastern South Africa, Swaziland, and central and southern Mozambique: Lower tropospheric divergence across southeastern Africa is expected to suppress rainfall in the region.. Confidence: Moderate Week-1 Outlook 06 – 12 December 2011

12. Experimental Week-2 Precipitation Outlooks Week-2 Outlook 13 – 19 December 2011 No forecast

13. Summary During the past seven days, below average rainfall was observed over local areas across the Gulf of Guinea coast, portions of southern Cameroon, much of Gabon, Congo, northern DRC, western Angola, central and eastern Zambia, central Tanzania, northern and southern Zimbabwe, Malawi, northern and southern Mozambique, southern and eastern Botswana, northeastern South Africa, Swaziland, and southern and western Madagascar. In contrast, moisture surpluses were observed across southern Ethiopia, much of Kenya, southern Somalia, parts of Uganda, western and southeastern Tanzania, central and southern Angola, local areas in Namibia, southern South Africa and northern Madagascar. During the past 30 days, above average rainfall was observed across eastern Guinea, coastal Cote D’Ivoire, local areas in southern Nigeria, southern and northern ends of Congo, western and southern DRC, much of Angola, northern Zambia, Uganda, portions of Tanzania, much of Kenya, southern Ethiopia, southern and central Somalia, northern Botswana, eastern Zimbabwe, southern Mozambique and parts of northern Madagascar. In contrast, eastern Liberia, portions of Cote D’Ivoire, southern Nigeria, many parts of Cameroon, Gabon, Equatorial Guinea, central Congo, CAR, central and northern DRC, parts of South Sudan Republic, southwest Ethiopia, eastern and central Namibia, southwestern Botswana, many places of South Africa, Lesotho, Swaziland and much of Madagascar had below average rainfall. During the past 90 days, moisture deficits were observed across southern Mauritania, Senegal, western Mali, portions of Burkina Faso, coastal Guinea, local areas in Nigeria, southern Cameroon, northern Gabon, central Sudan, western and eastern Ethiopia, parts of Namibia, southwestern Botswana, South Africa, Lesotho, parts of Mozambique and Madagascar. In contrast, central Mali, coastal Cote D’Ivoire, southern Ghana, Togo, southern Benin, local areas in Cameroon, Gabon, Congo, CAR, DRC, Uganda, northern Tanzania, much of Kenya, central and southern Somalia, southern Ethiopia, and southern South Sudan Republic received above average rainfall. Week-1 outlooks call for an increased chance for above average rainfall over southern Angola, northern Namibia western Botswana, northern Zambia, eastern DRC, eastern Uganda, much of Tanzania, southern Kenya, Malawi and northern Mozambique, while rainfall deficits are expected across portions of central and southeastern African countries.