The African Monsoon Recent Evolution and Current Status

1. The African Monsoon Recent Evolution and Current Status Update prepared by Climate Prediction Center / NCEP 07 December 2009 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 • Rainfall was above average over Gabon, southern Congo, northwest Angola, western and northwestern parts of DRC, pocket areas of Ethiopia, eastern Kenya and southern Somalia, parts of Zambia, Zimbabwe, southern and central Mozambique, northern parts of South Africa and Madagascar. • However, rainfall was deficient over Tanzania, northern Mozambique, southern and northern portions of DRC and parts of South

4. Rainfall Patterns: Last 7 Days During the past seven days, enhanced rainfall events were observed over Gabon, southern Congo, northwest Angola, western and northwestern parts of DRC, pocket areas of Ethiopia, eastern Kenya and southern Somalia, parts of Zambia, Zimbabwe, southern and central Mozambique, northern parts of South Africa and Madagascar. Rainfall was deficient over Tanzania, northern Mozambique, southern and northern portions of DRC and parts of South Africa.

5. Rainfall Patterns: Last 30 Days During the past 30 days rainfall was below average over parts of the Greater Horn of Africa, including Kenya, Uganda, southwestern Ethiopia, and southern Somalia. Rainfall was above average over Tanzania, much of DRC, Zambia, northern Zimbabwe, and southern Mozambique. However, light rains sustained moisture deficits over southern Madagascar, northern Mozambique, the area along the west coast of Angola. Rainfall was above average over much of Gabon, central Cameroon, and the areas along the Gulf of Guinea coastline.

6. Recent Rainfall Evolution Daily evolution of precipitation during the last 90 days at selected regions shows that moisture deficits remained steady along coastal Guinea and Cameroon (lower panel – left). Deficits are also observed over Uganda and surrounding region (lower panel – right) while southern Somalia recorded significant rainfall amounts (upper panel – right).

7. Atmospheric Circulation:Last 7 Days The 850 hPa wind anomaly (left panel) reflected an anomalous westerly wind flow across northern Africa and a weak anomalous cyclonic circulation centered along the Guinea coast. Also present are the southerlies over central and southern Africa. The 200 hPa wind anomaly reflected an anomalous anticyclonic circulation over northwest Africa and northerlies over southern Africa.

8. NCEP GEFS Model ForecastsNon-Bias Corrected Probability of precipitation exceedance Week-1: Valid 8 – 14 December, 2009Week-2: Valid 15 – 21 December, 2009 For week-1, the global ensemble forecast system (GEFS) suggests over a 90% chance for precipitation to exceed 25 mm over parts of central Africa, much of Zambia, eastern Angola, northern Botswana, Zimbabwe, central Mozambique, eastern South Africa, and Madagascar. The same for week-2, but with lower probabilities.

9. Experimental Week-1 Precipitation Outlooks Week-1 Outlook 8– 14 December, 2009 1. There is an increase chance for above average Precipitation over Gabon and southern parts of Congo and northern Angola: The anomalous convergence between a dry northerly and moist easterly flow is expected to enhance precipitation in the region. Confidence: Moderate 2. There is an increased chance for above average precipitation over eastern and central DRC:The Stronger than normal convergence over the Congo Air Boundary (CAB) area is expected to increase rainfall in the region. Confidence: Moderate 3. There is an increased chance for above average precipitation over southern Ethiopia, eastern Kenya and the adjacent areas of southern Somalia:The anomalous moist easterly flow and its associated convergence is expected to increase precipitation in the region. Confidence: Moderate

10. Experimental Week-2 Precipitation Outlooks Week-2 Outlook 15-21 December, 2009 No Forecast: Weak signal.

11. Summary • Enhanced rainfall events were observed over Gabon, southern Congo, northwest Angola, western and northwestern parts of DRC, pocket areas of Ethiopia, eastern Kenya and southern Somalia, parts of Zambia, Zimbabwe, southern and central Mozambique, northern parts of South Africa and Madagascar, while rainfall was deficient over Tanzania, northern Mozambique, southern and northern portions of DRC and parts of South Africa. • During the past 30 days rainfall was below average over parts of the Greater Horn of Africa, including Kenya, Uganda, southwestern Ethiopia, and southern Somalia. Rainfall was above average over Tanzania, much of DRC, Zambia, northern Zimbabwe, and southern Mozambique. However, light rains sustained moisture deficits over southern Madagascar, northern Mozambique, the area along the west coast of Angola. Rainfall was above average over much of Gabon, central Cameroon, and the areas along the Gulf of Guinea coastline. • For week1, there is an increased chance for above average rainfall over Gabon, southern Congo, northwestern Angola, parts of eastern Africa, central and eastern DRC.