The African Monsoon Recent Evolution and Current Status

The African Monsoon Recent Evolution and Current Status Include Week-1 and Week-2 Outlooks Update prepared by Climate Prediction Center / NCEP 17 December 2012 For more information, visit: http: //www. cpc. ncep. noaa. gov/products/Global_Monsoons/African_Monsoons/precip_monitoring. shtml

Outline • Highlights • Recent Evolution and Current Conditions • NCEP GEFS Forecasts • Summary

Highlights: Last 7 Days • Weekly total rainfall exceeded 75 mm over eastern DRC, many parts of Zambia, northern Mozambique, and local areas in Tanzania, South Africa and Madagascar. • Suppressed rainfall prevailed over portions of Angola, Namibia, much of Zimbabwe, and southern Mozambique. • Week-1 outlooks call for an increased chance for above-average rainfall over southern DRC, eastern Angola, much of Zambia, northern Botswana and northern Zimbabwe. In contrast, there is an increased chance for below-average rainfall over Southwest Angola, Northwest Namibia, eastern South Africa and the neighboring areas of Botswana and Zimbabwe, and southern Mozambique.

Rainfall Patterns: Last 7 Days During the past seven days, above-average rainfall was observed over southern Cote d’Ivoire, local areas in Gabon, Congo and Angola, many parts of DRC and Zambia, portions of Tanzania, northern Mozambique, local areas in Botswana, many parts of South Africa, and local areas in Madagascar. In contrast, southern Gabon, southern Congo, many parts of Angola and Namibia, local areas in DRC, western Tanzania, portions of Kenya and Zambia, much of Zimbabwe, Central and South Mozambique, local areas in South Africa, and portions of Madagascar.

Rainfall Patterns: Last 30 Days During the past 30 days, above-average rainfall was observed over portions of Guinea, Sierra Leone, Liberia, portions of Cote d’Ivoire, southern Ghana, local areas in Nigeria, Equatorial Guinea, much of Gabon, parts of DRC, Congo, Angola and Zambia, local areas in Namibia, Botswana, Mozambique, Tanzania and Kenya, and portions of South Africa and Madagascar. In contrast, local areas in Gabon, portions of DRC, local areas in Angola and Botswana, much of Zimbabwe, southern Zambia, southern Mozambique, local areas in South Africa, portions of Tanzania, Kenya, southern Somalia and northern Madagascar received below average rainfall.

Rainfall Patterns: Last 90 Days During the past 90 days, eastern Senegal, much of Guinea, Guinea-Bissau, Sierra Leone, local areas in Mali, Liberia, local areas in Burkina Faso and Cote d’Ivoire, Ghana, portions of Nigeria, Cameroon, CAR and DRC, much of Gabon, portions of South Sudan, portions of Angola, Uganda, local areas in Kenya, Southwest Ethiopia, and portions of Madagascar had above average rainfall. In contrast, rainfall was below average over local areas in East and Southeast Africa.

Rainfall Patterns: Last 180 Days During the past 180 days, rainfall was above-average over portions of Senegal, southern Mauritania, many parts of Mali, Guinea Bissau, Guinea, Sierra Leone, portions of Liberia, local areas in Cote d’Ivoire, much of Burkina Faso, Ghana and Benin, portions of Nigeria and Niger, southern Chad, northern Cameroon, much of CAR, portions of Gabon and DRC, portions of Angola, South Sudan, Uganda, western Kenya, local areas in Ethiopia, eastern South Africa and portions of Madagascar. Coastal Cote d’Ivoire, portions of Nigeria, local areas in Cameroon, Equatorial Guinea, northern Gabon, local areas in Congo and DRC, portions of Ethiopia, Eritrea, portions of Kenya and southern Somalia had below average rainfall.

Recent Rainfall Evolution Daily evolution of rainfall over the last 90 days at selected stations that the recent moderate rainfall helped to offset some of moisture deficits across portions of Zambia (bottom panel – left), and northern Mozambique (top panel right). In contrast, the recent decrease in rainfall sustained moisture deficits over portions of Zimbabwe (bottom panel –right).

Atmospheric Circulation: Last 7 Days The 850 h. Pa wind anomaly (left panel) featured anomalous lower level moist southeasterly to easterly winds across Southeast Africa, which may have contributed to the observed moderate to heavy rainfall in the region.

NCEP GEFS Model Forecasts Non-Bias Corrected Probability of precipitation exceedance Week-1: Valid 18 – 24 December 2012 Week-2: Valid 25 – 31 December 2012 For week-1 (left panel), there is an increased chance for rainfall to exceed 50 mm over southern Gabon, southern portions of DRC, eastern Angola, many parts of Zambia, northern Mozambique, western Tanzania, northern Zimbabwe, eastern South Africa and Madagascar. The probabilities of exceedance tend to decrease over Angola, Mozambique, and South Africa during week-2 (right panel)

Experimental Week-1 Precipitation Outlooks 18 – 24 December 2012 1. There is an increased chance for below average rainfall over Southwest Angola and Northwest Namibia: Lower level wind divergence is expected to suppress rainfall in the region. Confidence: Moderate 2. There is an increased chance for above average rainfall over southern DRC, eastern Angola, much of Zambia, northern Botswana and northern Zimbabwe: Anomalous lower level westerlies, with their associated cyclonic turning are expected to enhance rainfall in the region. Confidence: Moderate 3. There is an increased chance for below average rainfall over eastern South Africa and the neighboring areas of Botswana and Zimbabwe, and southern Mozambique: Combination of anomalous lower level divergence and upper level cyclonic flow is expected to suppress rainfall in the region. Confidence: Moderate

Experimental Week-2 Precipitation Outlooks 25 – 31 December 2012 1. There is an increased chance for above average rainfall over Southeast Angola, eastern Namibia, southern Zambia, Zimbabwe, and much of Botswana: Anomalous lower level wind convergence is expected to enhance rainfall in the region. Confidence: Moderate

Summary • During the past seven days, above-average rainfall was observed over southern Cote d’Ivoire, local areas in Gabon, Congo and Angola, many parts of DRC and Zambia, portions of Tanzania, northern Mozambique, local areas in Botswana, many parts of South Africa, and local areas in Madagascar. In contrast, southern Gabon, southern Congo, many parts of Angola and Namibia, local areas in DRC, western Tanzania, portions of Kenya and Zambia, much of Zimbabwe, Central and South Mozambique, local areas in South Africa, and portions of Madagascar. • During the past 30 days, above-average rainfall was observed over portions of Guinea, Sierra Leone, Liberia, portions of Cote d’Ivoire, southern Ghana, local areas in Nigeria, Equatorial Guinea, much of Gabon, parts of DRC, Congo, Angola and Zambia, local areas in Namibia, Botswana, Mozambique, Tanzania and Kenya, and portions of South Africa and Madagascar. In contrast, local areas in Gabon, portions of DRC, local areas in Angola and Botswana, much of Zimbabwe, southern Zambia, southern Mozambique, local areas in South Africa, portions of Tanzania, Kenya, southern Somalia and northern Madagascar received below average rainfall. • During the past 90 days, eastern Senegal, much of Guinea, Guinea-Bissau, Sierra Leone, local areas in Mali, Liberia, local areas in Burkina Faso and Cote d’Ivoire, Ghana, portions of Nigeria, Cameroon, CAR and DRC, much of Gabon, portions of South Sudan, portions of Angola, Uganda, local areas in Kenya, Southwest Ethiopia, and portions of Madagascar had above average rainfall. In contrast, rainfall was below average over local areas in East and Southeast Africa. • Week-1 outlooks call for an increased chance for above-average rainfall over southern DRC, eastern Angola, much of Zambia, northern Botswana and northern Zimbabwe. In contrast, there is an increased chance for below-average rainfall over Southwest Angola, Northwest Namibia, eastern South Africa and the neighboring areas of Botswana and Zimbabwe, and southern Mozambique.