The African Monsoon Recent Evolution and Current Status

1. The African Monsoon Recent Evolution and Current Status Update prepared by Climate Prediction Center / NCEP 21 March 2008 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 • Beneficial rains returned to South Africa for the second consecutive week, while light or no rain persisted over the southern areas of Mozambique and Zimbabwe. • Light or no rain continued to delay the onset of the rainy season in many areas in the Greater Horn of Africa, including Kenya and Ethiopia.

4. Overview • Over the past 7 days, moderate to heavy rains sustained moisture surpluses over many areas in southern Africa, including South Africa and Namibia. Moderate to heavy downpours also returned in above average rains over southeastern Angola, Zambia, northern Zimbabwe, central Mozambique, southern Malawi, western Botswana, and western Tanzania. Rainfall was near average over southwestern Kenya. However, light to moderate rains sustained moisture deficits in many areas of the Greater Horn of Africa, including most areas in Kenya, much of Ethiopia, where the Belg rains are yet to settle, southern Somalia, Uganda, Rwanda, and Burundi. Rainfall was also below average over the Gulf of Guinea region, while seasonably dry weather prevailed in the Sahel. • Over the last 30 days, the impact of TC Ivan and Jokwe resulted in above average rainfall rainfall along the west coast of Madagascar and portions of northern Mozambique. The wet conditions over the past week in South Africa resulted in above average rainfall for the last 30 days. Rainfall was also above average over portions of western Botswana, and central Namibia. However, lighter than average rains offset the impact of TCs Ivan and Jokwe and sustained moisture deficits along the east coast of Madagascar. Lower than average rains also sustained moisture deficits over southern Mozambique, Zimbabwe, eastern Botswana, most areas in Zambia, and portions of central Tanzania. Light rains also continued to sustain moisture deficits over most areas in Kenya, Ethiopia, southern Sudan, and Uganda. • Over the last 90 days, rainfall was overall above average over most areas in southern Africa, except for the southern areas of Mozambique and Zimbabwe, central Madagascar, northeastern Zambia, and northern Angola. • For the period 22-28 March 2008, the NCEP global ensemble forecasts (GEFS) suggests that there is a 90% chance or above for precipitation to exceed 50 mm over most areas in Tanzania, and southwestern Kenya, and local areas along the Gulf of Guinea coast. There is a 95% chance for precipitation to exceed 25 mm over the Kwazulu/Natal province of South Africa. According to the GEFS, the chance for moderate to heavy rains to occur in eastern Africa is weak.

5. Rainfall Patterns: Last 7 Days During the past 7 days, rainfall was again above average over portions of southern Africa, including northwestern Namibia, southeastern Angola, Zambia, northern Zimbabwe, central Mozambique and southern Malawi, the Maize Triangle of South Africa, western Botswana, and western Tanzania. Rainfall was also near average over southwestern Kenya, but was lower than average over eastern Kenya, Uganda, and Ethiopia, where the Belg rains are yet to settle.

6. Rainfall Patterns: Last 30 Days Over the last 30 days, rainfall was above average along the west coast of Madagascar and portions of northern Mozambique as a result of TCs Ivan and Jokwe. Rainfall was also above average over portions of northeastern South Africa, western Botswana, and central Namibia. However, lighter than average rains sustained moisture deficits along the east coast of Madagascar, southern Mozambique, Zimbabwe, eastern Botswana, most areas in Zambia, and portions of central Tanzania. Light rains also continued to sustain moisture deficits over most areas in the Greater Horn of Africa, central Africa, and the Gulf of Guinea region.

7. Rainfall Patterns: Last 90 Days Over the past 90 days, rainfall was above average over portions of southern Africa. The largest rainfall departures occurred over southern Angola, and northern Mozambique due in part to TCs Ivan and Jokwe. Rainfall was also above average over southern Zambia, central Mozambique, northern Botswana, and much of Namibia. Overall, Madagascar, received above average rainfall along its southwest and northeast coastal areas. Recent short term dryness sustained moisture deficits over the southern areas of Zimbabwe and Mozambique.

8. Recent Evolution: Rainfall Recently, southern Mozambique (top panel) received isolated heavy rains over the past 10 days, but not enough to offset the moisture deficits observed over the past several weeks. Since TC Jokwe, rainfall has been below average over southern Madagascar (middle panel). Crops in the Maize Triangle of South Africa benefited from heavy rainfall over the past week..

9. Atmospheric Circulation:Last 7 Days @ AH AM Over the past 7 days, low level easterly wind anomalies (left panel) persisted over the central Indian Ocean (IO) between 10 and 20S. The St. Helen and Mascarene high pressure systems (indicated by AH and AM on the left panel) also strengthened, creating favorable conditions for frontal systems to move across southern Africa. The moderate to heavy rains observed over South Africa over the last 7 days were also associated with the upper level atmospheric anomalous anticyclonic (counter clockwise) circulation (indicated with the @ sign on the right panel). The dryness over eastern Africa was associated with low level westerly wind anomalies over the equatorial IO.

10. NCEP GEFS Model ForecastsNon-Bias Corrected Probability of precipitation exceedance – Week-1Valid Mar 22-28, 2008 The NCEP global ensemble forecast system (GEFS) suggest that there is a 90% chance or above for precipitation to exceed 50 mm over most areas in Tanzania, and southwestern Kenya, and local areas along the Gulf of Guinea coast line. There is a 95% chance for precipitation to exceed 25 mm over the Kwazulu/Natal province of South Africa. According to the GEFS, the chance for moderate to heavy rains to occur in eastern Africa is weak.

11. Summary • Over the past 7 days, moderate to heavy rains sustained moisture surpluses over many areas in southern Africa, including South Africa and Namibia. Moderate to heavy downpours also returned in above average rains over southeastern Angola, Zambia, northern Zimbabwe, central Mozambique, southern Malawi, western Botswana, and western Tanzania. Rainfall was near average over southwestern Kenya. However, light to moderate rains sustained moisture deficits in many areas of the Greater Horn of Africa, including most areas in Kenya, much of Ethiopia, where the Belg rains are yet to settle, southern Somalia, Uganda, Rwanda, and Burundi. Rainfall was also below average over the Gulf of Guinea region, while seasonably dry weather prevailed in the Sahel. • Over the last 30 days, the impact of TC Ivan and Jokwe resulted in above average rainfall rainfall along the west coast of Madagascar and portions of northern Mozambique. The wet conditions over the past week in South Africa resulted in above average rainfall for the last 30 days. Rainfall was also above average over portions of western Botswana, and central Namibia. However, lighter than average rains offset the impact of TCs Ivan and Jokwe and sustained moisture deficits along the east coast of Madagascar. Lower than average rains also sustained moisture deficits over southern Mozambique, Zimbabwe, eastern Botswana, most areas in Zambia, and portions of central Tanzania. Light rains also continued to sustain moisture deficits over most areas in Kenya, Ethiopia, southern Sudan, and Uganda. • Over the last 90 days, rainfall was overall above average over most areas in southern Africa, except for the southern areas of Mozambique and Zimbabwe, central Madagascar, northeastern Zambia, and northern Angola. • For the period 22-28 March 2008, the NCEP global ensemble forecasts (GEFS) suggests that there is a 90% chance or above for precipitation to exceed 50 mm over most areas in Tanzania, and southwestern Kenya, and local areas along the Gulf of Guinea coast. There is a 95% chance for precipitation to exceed 25 mm over the Kwazulu/Natal province of South Africa. According to the GEFS, the chance for moderate to heavy rains to occur in eastern Africa is weak.