The African Monsoon Recent Evolution and Current Status Update prepared by Climate Prediction Center / NCEP 6 December 2010 For more information, visit:

Outline Highlights Recent Evolution and Current Conditions NCEP GEFS Forecasts Summary

Highlights: Last 7 Days In East Africa, light rains continued to sustain moisture deficits over many areas including Kenya and southern Somalia. Rainfall deficits also persisted in eastern DRC. Heavy downpours may have resulted in flooding in local areas in southern Africa, including central Mozambique.

Rainfall Patterns: Last 7 Days During the past seven days, little or no rain sustained moisture deficits in eastern Africa. Below average rainfall was also evident in eastern Gabon and Congo, and persisted over much of DRC. Further south, however, in the northern areas of southern Africa, heavy downpours drenched much of this region, and may have resulted in flooding in local areas, especially central Mozambique, where the heaviest rains occurred. Rainfall was also above average over portions of western Madagascar. In contrast, rainfall was below average over most areas in the Maize Triangle of South Africa (except for pockets in the area bordering southern Mozambique) and along the east coast of Madagascar.

Rainfall Patterns: Last 30 Days During the past 30 days, in West Africa moisture remains confined along the Gulf of Guinea coastline, while seasonably dry conditions prevailed in the Sahel. In Central Africa, rainfall was above average over pockets in central Cameroon, western Gabon, most areas in Congo, and southern CAR. Rainfall was below average over much of DRC. In East Africa, rainfall was below average across the region from southern Ethiopia southward to Tanzania. In southern Africa, heavy downpours resulted in moisture surpluses across much of the eastern sector of the region including central and southern Mozambique, southern Malawi, Zimbabwe, Botswana, northwestern Namibia, southeastern Angola, and portions of western Zambia. Rainfall was below average over pockets in in the Maize Triangle of South Africa.

Rainfall Patterns: Last 90 Days During the past 90 days, rainfall was above average over pockets in West Africa. Rainfall was also locally above average over western CAR, parts of Gabon, and central Congo. Rainfall was below average over much of eastern DRC eastward to most areas in eastern Africa. Rainfall was above average over central Mozambique and local areas in eastern Zimbabwe.

Rainfall Patterns: Last 180 Days During the past 180 days, rainfall was above average over much of West Africa, except for local areas in The Gambia, Sierra Leone and central Nigeria. Rainfall was also above average over parts of central Africa including southern Chad, southern Cameroon, northern Congo, and southern Gabon. Rainfall was below average over eastern DRC. In east Africa, rainfall was above average over northern Ethiopia, and below average locally over central Kenya and southern Somalia.

Recent Rainfall Evolution Daily evolution of precipitation at selected stations indicates that despite episodic heavy rains, moisture deficits persisted in most areas of the Maize Triangle of South Africa (lower panel – left). Recent heavy rains sustained the moisture surpluses accumulated over the past two weeks in central Mozambique (lower panel – right). Light rains sustained moisture deficits in parts of Kenya (upper panel – right ).

Atmospheric Circulation: Last 7 Days The 850 hPa wind anomalies (right panel) featured easterlies across much of East African and the Indian Ocean, which contributed to the rainfall deficits in this region. In southern Africa, an anomalous cyclonic circulation centered over South Africa, and the strengthening of both the Saint Helen and Mascarene High Pressure Systems may have helped stir the moisture surpluses observed in this region. The 200 hPa wind anomaly map (left panel) supported this evidence with upper level divergence in much of southern Africa, and consistent with the lower level circulation.

NCEP GEFS Model Forecasts Non-Bias Corrected Probability of precipitation exceedance Week-1: Valid December 2010 Week-2: Valid December, 2010 For week-1, there is a high chance for precipitation to exceed 50 mm over portions of central and southern Africa, including Gabon, southern Congo and DRC, and southeastern Angola. For week-2, rainfall is likely to exceed 50mm over Gabon, portions of Zambia, northern Zimbabwe, and Madagascar.

1.There is an increased chance for above average rainfall over parts of the northern areas of southern Africa in the areas including Mozambique, Malawi, Zambia, and Zimbabwe: A nomalous low level convergence across the central and eastern parts of southern African countries is expected to enhance rainfall in this region. Confidence: Moderate 2.There is an increased chance for below average rainfall over southern Somalia, Kenya and northern Tanzania: Anomalous dry easterlies are expected to suppress precipitation in this region. Confidence: Moderate Experimental Week-1 Precipitation Outlooks Week-1 Outlook 7 – 13 December, 2010

Experimental Week-2 Precipitation Outlooks Week-2 Outlook 14 – 20 December, 2010 No forecast.

Summary During the past seven days, little or no rain sustained moisture deficits in eastern Africa. Below average rainfall was also evident in eastern Gabon and Congo, and persisted over much of DRC. Further south, however, in the northern areas of southern Africa, heavy downpours drenched much of this region, and may have resulted in flooding in local areas, especially central Mozambique, where the heaviest rains occurred. Rainfall was also above average over portions of western Madagascar. In contrast, rainfall was below average over most areas in the Maize Triangle of South Africa (except for pockets in the area bordering southern Mozambique) and along the east coast of Madagascar. During the past 30 days, in West Africa moisture remains confined along the Gulf of Guinea coastline, while seasonably dry conditions prevailed in the Sahel. In Central Africa, rainfall was above average over pockets in central Cameroon, western Gabon, most areas in Congo, and southern CAR. Rainfall was below average over much of DRC. In East Africa, rainfall was below average across the region from southern Ethiopia southward to Tanzania. In southern Africa, heavy downpours resulted in moisture surpluses across much of the eastern sector of the region including central and southern Mozambique, southern Malawi, Zimbabwe, Botswana, northwestern Namibia, southeastern Angola, and portions of western Zambia. Rainfall was below average over pockets in in the Maize Triangle of South Africa. During the past 90 days, rainfall was above average over pockets in West Africa. Rainfall was also locally above average over western CAR, parts of Gabon, and central Congo. Rainfall was below average over much of eastern DRC eastward to most areas in eastern Africa. Rainfall was above average over central Mozambique and local areas in eastern Zimbabwe. For week-1, there is an increased chance for above average rainfall over parts of the northern areas of southern Africa in the areas including Mozambique, Malawi, Zambia, and Zimbabwe. There is an increased chance for below average rainfall over southern Somalia, Kenya, and northern Tanzania