The African Monsoon Recent Evolution and Current Status

1. The African Monsoon Recent Evolution and Current Status Update prepared by Climate Prediction Center / NCEP 28 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 • Areas in East Africa benefited from the northward shift of the Intertropical Convergence Zone (ITCZ) as heavier than average rains fell over northern Tanzania and southern Kenya. Rainfall was significantly below average over southern DRC, and the northern areas of Angola and Zambia. • Light or no rain continued to delay the onset of the rainy season in many areas in the Greater Horn of Africa, including northern Kenya and Ethiopia. Rainfall was slightly below average over parts of the Gulf of Guinea region.

4. Rainfall Patterns: Last 7 Days During the past 7 days, the area of maximum rainfall shifted north to include northern Tanzania, and the southern areas of Kenya and Uganda. Southwestern Ethiopia and the Gulf of Guinea region received light rains. Rainfall was below average over the northern areas of Angola, Zambia, Mozambique, and Madagascar. Rainfall was also below average over southern DRC and Malawi.

5. Rainfall Patterns: Last 30 Days Over the last 30 days, rainfall was above average over northern Tanzania, local areas in northern Mozambique and western Botswana, northwestern Nambia, and portions of eastern South Africa. Rainfall was below average over the northern areas of Zambia and Angola, the southern areas of DRC and Congo, and local areas in northern Cameroon and the Gulf of Guinea region.

6. 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. 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, Mozambique, and Ethiopia.

7. Recent Rainfall Evolution Slow onset of the Belg rains in southern Ethiopia (top panel - right); Adequate moisture in southwestern Kenya (bottom panel – right); Rainfall decrease in the Gulf of Guinea region over the past two weeks.

8. Atmospheric Circulation:Last 7 Days L Over the past 7 days, low level westerly wind anomalies (left panel) persisted over the central Indian Ocean (IO) between 10 and 20S. A tropical low pressure system indicated with “L” was evident northeast of Madagascar. The tropical low moved southeastward and did not affect Madagascar. The light rains observed over Ethiopia over the last 7 days were also associated with the upper level easterly wind anomalies (right panel) across the central IO.

9. NCEP GEFS Model ForecastsNon-Bias Corrected Probability of precipitation exceedance – Week-1Valid Mar 29 - Apr 4, 2008 The NCEP global ensemble forecast system (GEFS) suggests a low tilt in the odds (20-40%) for precipitation to exceed 50 mm over the southwestern areas of Kenya and Ethiopia (right panel). The odds are higher for these areas for the 25 mm threshold (right panel).

10. Summary • Over the past seven days, as the Intertropical Convergence Zone (ITCZ) began its northward shift, rainfall diminished significantly in southern Africa. However, local areas on eastern South Africa and southern Mozambique received above average rainfall. Rainfall was significantly below average over the northern areas of Angola and Zambia, and southern DRC, as the area of maximum rainfall shifted to northern Tanzania, southern Kenya, and Uganda, where moderate to heavy showers resulted in above average rainfall. However, light rain fell over southwestern Ethiopia and the southern tip of Somalia, while dry conditions prevailed elsewhere. Most areas in the Gulf of Guinea region also received light rains. Rainfall was below average over the area encompassing southeastern Cote d’Ivoire and southwestern Ghana. Seasonably dry weather prevailed across the Sahel. • Over the last 30 days, the wet conditions of the past week resulted in above average rainfall in northern Tanzania and southern Kenya. Rainfall was also above average over local areas in northern Mozambique and southern Malawi, northeastern South Africa, local areas in western Botswana, and northern Namibia. Lower than average rains resulted in moisture deficits over the northern areas of Angola and Zambia, southern DRC, and Madagascar. In Ethiopia, the Belg season continued to be delayed in many areas as light or no rain sustained moisture deficits. Rainfall was below average over local areas in the Gulf of Guinea region. • Over the last 90 days, rainfall was overall above average over most areas in Namibia, southern Angola, southwestern Zambia, eastern Mozambique, Tanzania, and parts of Madagascar. Rainfall was below average over portions of central Africa, Uganda, southwestern Kenya, and Ethiopia. • For the period 29 March – 4 April 2008, the NCEP global ensemble forecast system (GEFS) suggests a low tilt in the odds to favor above average rainfall over most areas in eastern Africa.