The African Monsoon Recent Evolution and Current Status Include Week-1 and Week-2 Outlooks Update prepared by Climate Prediction Center / NCEP 7 February 2011 For more information, visit:

Outline Highlights Recent Evolution and Current Conditions NCEP GEFS Forecasts Summary

Highlights: Last 7 Days Flood threats diminished significantly over the Zambezi and other river basins in southern Africa as rainfall amounts were significantly lower over the past week. Extremely heavy rainfall soaked northern and southern Madagascar to sustain moisture surpluses and flooding in local areas. Week-1 outlooks call for an increased chance for above average rainfall along coastal Angola and over the northern sector of the Mozambique Channel basin including Madagascar. There is an increased chance for below average rainfall over the Maize Triangle of South Africa.

Rainfall Patterns: Last 7 Days During the past seven days, heavy rains soaked the northern and southern sectors of Madagascar. However, rainfall eased in most areas in continental southern Africa. Amounts decreased significantly in Zambia, Zimbabwe, and central Mozambique, alleviating flood threats along the Zambezi and other river basins. Rainfall was only slightly above average over the central areas of Zimbabwe and Mozambique. Light rains fell over most areas in the Maize Triangle of South Africa and eastern Botswana. Rainfall was significantly below average over eastern Angola, the northern areas of Zambia and Mozambique, central Tanzania, southern DRC, central Congo, and much of Gabon.

Rainfall Patterns: Last 30 Days During the past 30 days, rainfall was above average over southern and northern Madagascar and much of continental southern Africa. However, rainfall was below average along the central east coast of Madagascar, most areas northern southern Africa and eastern Africa from northern Mozambique northward into Kenya and DRC.

Rainfall Patterns: Last 90 Days During the past 90 days, rainfall was above average over southern and northern Madagascar and much of continental southern Africa, except for northern Mozambique, Malawi, Tanzania, Zambia, eastern Angola, and DRC. Rainfall was also below average over eastern Africa.

Rainfall Patterns: Last 180 Days During the past 180 days, rainfall was above average over much of West Africa, except for Sierra Leone. Rainfall was also above over parts of southern Africa. Rainfall was below average over most areas in northern southern Africa, central, and eastern Africa.

Recent Rainfall Evolution Daily evolution of precipitation at selected stations indicates season-to-date moisture surpluses in parts of the Maize Triangle of South Africa despite a reduction in rainfall amounts over the past week (lower panel – left). Moisture surpluses held steady in central Mozambique (lower panel – right). Rainfall continued to be steady but below average over southwestern Tanzania (upper panel – right ).

Atmospheric Circulation: Last 7 Days The 850 hPa wind anomaly (left panel) featured an anomalous cyclonic circulation centered southeast of Madagascar. This pattern contributed to the above average rainfall in Madagascar. However, an upper level trough along the Mozambique Channel evident in the 200 hPa wind anomaly (right panel) contributed to the suppressed rainfall over parts of continental southern Africa.

NCEP GEFS Model Forecasts Non-Bias Corrected Probability of precipitation exceedance Week-1: Valid February 2011 Week-2: Valid February, 2011 For week-1, there is a high chance for precipitation to exceed 50 mm over the northern areas of Mozambique and Zambia, and parts of Angola. Same areas for week-2, but with lower probabilities.

Experimental Week-1 Precipitation Outlooks Week-1 Outlook 8 – 14 February, There is an increased chance for above average rainfall along coastal Angola: Anomalous low level westerlies from the southeastern Atlantic are expected to enhance rainfall in this region. Confidence: Moderate 2.There is an increased chance for above average rainfall in the area encompassing eastern Zambia, Malawi, northern Mozambique, and Madagascar: Anomalous cyclonic circulation in the vicinity of the Mozambique Channel is expected to enhance rainfall in this region. Confidence: Moderate. 3.There is an increased chance for below average rainfall over parts of the Maize Triangle of south Africa, the southern areas of Mozambique and Zimbabwe, and eastern Botswana: Lower tropospheric anticyclonic anomaly is expected to suppress rainfall in this region. Confidence: Moderate

Experimental Week-2 Precipitation Outlooks Week-2 Outlook 15 – 21 February 2011 No forecast

Summary During the past seven days, heavy rains soaked the northern and southern sectors of Madagascar. However, rainfall eased in most areas in continental southern Africa. Amounts decreased significantly in Zambia, Zimbabwe, and central Mozambique, alleviating flood threats along the Zambezi and other river basins. Rainfall was only slightly above average over the central areas of Zimbabwe and Mozambique. Light rains fell over most areas in the Maize Triangle of South Africa and eastern Botswana. Rainfall was significantly below average over eastern Angola, the northern areas of Zambia and Mozambique, central Tanzania, southern DRC, central Congo, and much of Gabon. During the past 30 days, rainfall was above average over southern and northern Madagascar and much of continental southern Africa. However, rainfall was below average along the central east coast of Madagascar, most areas northern southern Africa and eastern Africa from northern Mozambique northward into Kenya and DRC. During the past 90 days, rainfall was above average over southern and northern Madagascar and much of continental southern Africa, except for northern Mozambique, Malawi, Tanzania, Zambia, eastern Angola, and DRC. Rainfall was also below average over eastern Africa. For week-1, There is an increased chance for above average rainfall along coastal Angola. There is also an increased chance for above average rainfall in the area encompassing eastern Zambia, Malawi, northern Mozambique, and Madagascar. For week-2, there is an increased chance for below average rainfall over parts of the Maize Triangle of south Africa, the southern areas of Mozambique and Zimbabwe, and eastern Botswana.