The African Monsoon Recent Evolution and Current Status Update prepared by Climate Prediction Center / NCEP 15 November 2010 For more information, visit:

Outline Highlights Recent Evolution and Current Conditions NCEP GEFS Forecasts Summary

Highlights: Last 7 Days Moisture deficits continued to persist over most areas in eastern Africa. Moderate to heavy rains sustained moisture surpluses in portions of southern Africa. The exceptions however were eastern Tanzania, central Mozambique, and Madagascar, where rainfall was significantly below average.

Rainfall Patterns: Last 7 Days During the past seven days, rainfall was slightly below average over portions of the Gulf of Guinea region, except for local areas in Ghana and southwestern Nigeria that registered moisture surpluses. Rainfall was also below average over most areas in central Africa and eastern Africa. In contrast parts of southern Africa recorded abundant rains. Rainfall was above average along the northwest-southeast band from southern DRC to eastern South Africa. However, rainfall was below average over most of Tanzania, central Mozambique, and Madagascar.

Rainfall Patterns: Last 30 Days During the past 30 days, rainfall was near average across much of the Sahel and above average over the Gulf of Guinea region, except for parts of Sierra Leone, and local areas in southeastern Nigeria. In central Africa, rainfall was above average over much of Cameroon, Equatorial Guinea, western Gabon, the area along the boundary between Congo and DRC, and western CAR. Rainfall was below average over eastern and southern DRC. In East Africa, central Sudan received above average rainfall. However, moisture deficits spread from Ethiopia and southern Sudan southward to Tanzania, except for few local areas that registered above average rainfall. Local areas in southern Mozambique, Zimbabwe, western Zambia, and eastern Botswana also received above average rainfall, while much of southern Africa experienced below average rainfall.

Rainfall Patterns: Last 90 Days During the past 90 days, rainfall was above average over most parts West Africa except for western Guinea, Sierra Leone, southern Ghana and much of central and eastern Nigeria. In eastern and central Africa, rainfall was above average over parts CAR, Gabon, Congo Republic and northern Ethiopia. Most parts of DRC, parts of southern Sudan, Angola, southern Ethiopia, Somalia and South Africa had below average precipitation.

Rainfall Patterns: Last 180 Days During the past 180 days, rainfall was above average over much of West Africa, except for local areas in western Guinea, Sierra Leone, Liberia, southern Ghana, and much of central and eastern Nigeria. Rainfall was also above average over, parts of Gabon and Congo Republic, eastern DRC and eastern Kenya. Huge moisture surpluses were recorded over southern Chad, CAR and northern Ethiopia, with pockets in southern Somalia and Madagascar. Elsewhere in eastern and central Africa, precipitation was below average.

Recent Rainfall Evolution Daily evolution of precipitation at selected stations indicates that rainfall has been steadily increasing over parts of the Gulf of Guinea region (lower panel – left). The rainfall season has been off to a slow start in portions of southern Africa (lower panel – right). Steady but below average rains continued to fall over parts of eastern Africa (upper panel – right ).

Atmospheric Circulation: Last 7 Days The westerly wind anomalies from the equatorial eastern Atlantic that persisted over West Africa at 850hPa (left panel) have weakened. A westerly trough over the Mediterranean stretching equatorward into West Africa was evident. The 200 hPa wind anomaly shows a cyclonic vortex displaced to the west of the position of the trough at 850hPa. This, together with the trough at 850hpa, may likely have perturbed the ITCZ causing some localized precipitation in parts of West Africa. Low level anticyclonic flow located southewest of Lake Victoria and westerly wind anomalies over the northern Indian Ocean may have contributed to the inhibition of precipitation over may parts of central, eastern, and southern Africa.

NCEP GEFS Model Forecasts Non-Bias Corrected Probability of precipitation exceedance Week-1: Valid November 2010 Week-2: Valid November, 2010 For week-1, there is a high chance for precipitation to exceed 50 mm over portions of central and southern Africa. For week-2, rainfall is likely to exceed 50mm over Liberia and most parts of central and southern Africa.

1. There is an increased chance for above average rainfall along the central coast of Africa from Gabon southward to Tanzania: Anomalous westerly winds from the Atlantic Ocean and their associated convergence across the western parts of equatorial and southern Africa are expected to enhance rainfall in the region. Confidence: Moderate 2. There is an increased chance for below average rainfall over the eastern parts of the horn of Africa: The anomalous dry northwesterly winds are expected to suppress rainfall in this region. Confidence: Moderate Experimental Week-1 Precipitation Outlooks Week-1 Outlook 16 – 22 November, 2010

Experimental Week-2 Precipitation Outlooks Week-2 Outlook November, 2010 No forecast.

Summary During the past seven days, rainfall was slightly below average over portions of the Gulf of Guinea region, except for local areas in Ghana and southwestern Nigeria that registered moisture surpluses. Rainfall was also below average over most areas in central Africa and eastern Africa. In contrast parts of southern Africa recorded abundant rains. Rainfall was above average along the northwest-southeast band from southern DRC to eastern South Africa. However, rainfall was below average over most of Tanzania, central Mozambique, and Madagascar. During the past 30 days, rainfall was near average across much of the Sahel and above average over the Gulf of Guinea region, except for parts of Sierra Leone, and local areas in southeastern Nigeria. In central Africa, rainfall was above average over much of Cameroon, Equatorial Guinea, western Gabon, the area along the boundary between Congo and DRC, and western CAR. Rainfall was below average over eastern and southern DRC. In East Africa, central Sudan received above average rainfall. However, moisture deficits spread from Ethiopia and southern Sudan southward to Tanzania, except for few local areas that registered above average rainfall. Local areas in southern Mozambique, Zimbabwe, western Zambia, and eastern Botswana also received above average rainfall, while much of southern Africa experienced below average rainfall. During the past 90 days, rainfall was above average over most parts West Africa except for western Guinea, Sierra Leone, southern Ghana and much of central and eastern Nigeria. In eastern and central Africa, rainfall was above average over parts CAR, Gabon, Congo Republic and northern Ethiopia. Most parts of DRC, parts of southern Sudan, Angola, southern Ethiopia, Somalia and South Africa had below average precipitation. For week-1, there is an increased chance for above average rainfall along the central coast of Africa from Gabon southward to Tanzania. For week-2, there is an increased chance for below average rainfall over the eastern parts of the horn of Africa