African Monsoon: Recent Evolution & Current Status

1. The African Monsoon Recent Evolution and Current StatusInclude Week-1 and Week-2 Outlooks Update prepared by Climate Prediction Center / NCEP 17 January 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 120mm across southern and northwestern Madagascar, the Comoros Islands, and portions of northern Mozambique. • Return of moderate to locally heavy rainfall resulted in moisture surpluses across portions of southern Angola, western and central DRC, and western Tanzania. • Week-1 outlooks call for an increased chance for above average rainfall over southern Angola, northern Namibia, southern Tanzania, Malawi, eastern Zambia, northern Zimbabwe, much of Mozambique, the Comoros Islands and western Madagascar.

4. Rainfall Patterns: Last 7 Days During the past seven days, above average rainfall was observed over local areas in Gabon, western and central DRC, southern Angola, local areas in northern Namibia, southern Botswana and South Africa, eastern end of Zambia, western and southern Tanzania, northern Mozambique, northwestern and southern Madagascar, and the Comoros Islands. In contrast, below average rainfall was observed over southern Gabon, many parts of Congo, portions of northern and southern DRC, parts of Uganda, southwestern Kenya, northern Tanzania, many parts of Zambia, Botswana, Zimbabwe, central and southern Mozambique, portions of South Africa and central Madagascar.

5. Rainfall Patterns: Last 30 Days During the past 30 days, much of Gabon, Equatorial Guinea, Congo, many parts of DRC, portions of northern Angola, many parts of Zambia, southern Malawi, central and southern Mozambique, portions of South Africa, central Namibia, many parts of Botswana, western and southern Zimbabwe, portions of South Africa, much of Uganda, Kenya, southwestern Ethiopia, and southwestern and northeastern coast of Madagascar received below average rainfall. In contrast, above average rainfall was observed over local areas in DRC, central and southern Angola, parts of Malawi, northern Namibia, northeastern Zimbabwe, northern Mozambique, many parts of Tanzania and much of Madagascar.

6. Rainfall Patterns: Last 90 Days During the past 90 days, central Congo, western DRC, parts of Uganda, much of Tanzania, Kenya, southern Somalia, southern Ethiopia, western Zambia, portions of Angola, local areas in northern Botswana, coastal Mozambique and northern coast of Madagascar received above average rainfall. Below average rainfall was observed across southwestern Cameroon, much of Gabon, Equatorial Guinea, northern DRC, central Zambia, local areas in Botswana, portions of South Africa, central Mozambique and portions of Madagascar.

7. Rainfall Patterns: Last 180 Days During the past 180 days, rainfall was above average across northern Guinea, central Mali, local areas in Chad, parts of Congo, CAR, portions of DRC, southern South Sudan Republic, Uganda, much of Kenya, Rwanda, Burundi, southern Ethiopia, central and southern Somalia, many parts of Tanzania, portions of Angola, western Zambia and northern Botswana. Moisture deficits were observed across southern Mauritania, southern Senegal, coastal Guinea Conakry, Sierra Leone, western Burkina Faso and western Niger, portions of Nigeria, southern Cameroon, northern Gabon, eastern Sudan, Eritrea, portions of Ethiopia, portions of South Africa, central Mozambique and parts of Madagascar.

8. Recent Rainfall Evolution Daily evolution of rainfall over the last 90 days at selected stations reflects rainfall deficits that prevailed over Gabon (bottom panel-left), central Mozambique (top panel – right) and northeastern South Africa (bottom panel – right).

9. Atmospheric Circulation:Last 7 Days The 850hPa wind anomaly (left panel) featured anomalous cyclonic circulation in the vicinity of the Mozambique Channel, which may have contributed to observed heavy rainfall across southeastern Africa. The moist westerly anomalies from the Atlantic Ocean may have also contributed to the observed moisture surpluses across portions of Angola. The 200hPa wind anomaly (right panel) featured stronger than normal subtropical westerly jet across Northeast Africa and the neighboring areas.

10. NCEP GEFS Model ForecastsNon-Bias Corrected Probability of precipitation exceedance Week-1: Valid 18 – 24 January 2012Week-2: Valid 25 – 31 January 2012 For week-1 (left panel), there is an increased chance for rainfall to exceed 50 mm over southeastern Africa, including the Mozambique Channel and western Madagascar. For week 2 (right panel), the probabilities of exceedence tend to decrease over many parts of the Mozambique Channel.

11. Experimental Week-1 Precipitation Outlooks Week-1 Outlook 18 – 24 January 2012 • There is an increased chance for below average rainfall over northeastern Angola, southern DRC, Rwanda, Burundi and western Tanzania : Anomalous lower tropospheric divergence is expected to suppress rainfall in the region. Confidence: Moderate • There is an increased chance for above average rainfall along the Angola-Namibia border: 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 Zambia, Malawi, southern Tanzania, northern Zimbabwe, Mozambique, the Mozambique Channel and western Madagascar: Anomalous cyclonic circulation in the Mozambique Channel is expected to enhance rainfall in the region. Confidence: Moderate

12. Experimental Week-2 Precipitation Outlooks Week-2 Outlook 25 – 31 January 2012 • There is an increased chance for below average rainfall over eastern Namibia, Botswana, and parts of South Africa: Anomalous lower tropospheric divergence is expected to suppress rainfall in the region. Confidence: Moderate • There is an increased chance for above average rainfall over southern Mozambique and Madagascar: Anomalous cyclonic shear in the Vicinity of the Mozambique Channel and the neighboring areas of the Indian Ocean is expected to enhance rainfall in the region. Confidence: Moderate

13. Summary During the past seven days, above average rainfall was observed over local areas in Gabon, western and central DRC, southern Angola, local areas in northern Namibia, southern Botswana and South Africa, eastern end of Zambia, western and southern Tanzania, northern Mozambique, northwestern and southern Madagascar, and the Comoros Islands. In contrast, below average rainfall was observed over southern Gabon, many parts of Congo, portions of northern and southern DRC, parts of Uganda, southwestern Kenya, northern Tanzania, many parts of Zambia, Botswana, Zimbabwe, central and southern Mozambique, portions of South Africa and central Madagascar. During the past 30 days, much of Gabon, Equatorial Guinea, Congo, many parts of DRC, portions of northern Angola, many parts of Zambia, southern Malawi, central and southern Mozambique, portions of South Africa, central Namibia, many parts of Botswana, western and southern Zimbabwe, portions of South Africa, much of Uganda, Kenya, southwestern Ethiopia, and southwestern and northeastern coast of Madagascar received below average rainfall. In contrast, above average rainfall was observed over local areas in DRC, central and southern Angola, parts of Malawi, northern Namibia, northeastern Zimbabwe, northern Mozambique, many parts of Tanzania and much of Madagascar. During the past 90 days, central Congo, western DRC, parts of Uganda, much of Tanzania, Kenya, southern Somalia, southern Ethiopia, western Zambia, portions of Angola, local areas in northern Botswana, coastal Mozambique and northern coast of Madagascar received above average rainfall. Below average rainfall was observed across southwestern Cameroon, much of Gabon, Equatorial Guinea, northern DRC, central Zambia, local areas in Botswana, portions of South Africa, central Mozambique and portions of Madagascar. Week-1 outlooks call for an increased chance for above average rainfall over southern Angola, northern Namibia, southern Tanzania, Malawi, eastern Zambia, northern Zimbabwe, much of Mozambique, the Comoros Islands and western Madagascar.