The African Monsoon Recent Evolution and Current Status

1. The African Monsoon Recent Evolution and Current Status Update prepared by Climate Prediction Center / NCEP 14 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 • During the past seven days, enhanced rainfall events were observed over Gabon, southern Congo, parts of eastern Angola, northwestern parts of DRC, parts of southern Ethiopia, much of Uganda, parts of western Kenya, southern Somalia, parts of northern Tanzania, southern Zambia, Botswana, Zimbabwe, parts of South Africa Republic and northern Madagascar. • Rainfall was deficient over central and southern Tanzania, much of Mozambique, western parts of South Africa Republic and southern Madagascar.

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

5. Rainfall Patterns: Last 30 Days During the past 30 days rainfall was below average over parts of the Greater Horn of Africa, central Tanzania, northern Mozambique and southwestern Angola. Rainfall was above average over Gabon, parts of DRC, eastern Angola, Zambia, much of Zimbabwe, northern Botswana, southern Mozambique, northern South Africa Republic and northern Madagascar.

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 central Africa and a weak anomalous cyclonic circulation centered in the southern Atlantic west of southern Africa. The 200 hPa wind anomaly (right panel) reflected an anomalous anticyclonic circulation centered over Mozambique channel and westerly flow over northern Africa.

8. NCEP GEFS Model ForecastsNon-Bias Corrected Probability of precipitation exceedance Week-1: Valid 15 – 21 December, 2009Week-2: Valid 22 – 28 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 Mozambique and Madagascar. The same for week-2, but with slightly lower probabilities.

9. Experimental Week-1 Precipitation Outlooks Week-1 Outlook 15– 21 December, 2009 1. There is an increase chance for above average Precipitation over parts of southern DRC, eastern Angola, much of Zambia, Malawi and northern Mozambique: The anomalous westerly flow from the Atlantic Ocean and its associated convergence is expected to enhance precipitation in the region. Confidence: Moderate 2. There is an increased chance for above average precipitation over northern Madagascar:The Stronger than normal onshore wind is expected to increase rainfall in the region. Confidence: Moderate

10. Experimental Week-2 Precipitation Outlooks Week-2 Outlook 22-28 December, 2009 No Forecast: Weak signal. Confidence: Moderate

11. Summary • During the past seven days, enhanced rainfall events were observed over Gabon, southern Congo, parts of eastern Angola, northwestern parts of DRC, parts of southern Ethiopia, much of Uganda, parts of western Kenya, southern Somalia, parts of northern Tanzania, southern Zambia, Botswana, Zimbabwe, parts of South Africa Republic and northern Madagascar. Rainfall was deficient over central and southern Tanzania, much of Mozambique, western parts of South Africa Republic and southern Madagascar. • During the past 30 days rainfall was below average over parts of the Greater Horn of Africa, central Tanzania, northern Mozambique and southwestern Angola. Rainfall was above average over Gabon, parts of DRC, eastern Angola, Zambia, much of Zimbabwe, northern Botswana, southern Mozambique, northern South Africa Republic and northern Madagascar. • 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 Mozambique and Madagascar. The same for week-2, but with slightly lower probabilities.