The African Monsoon Recent Evolution and Current Status

1. The African Monsoon Recent Evolution and Current Status Update prepared by Climate Prediction Center / NCEP 04 May 2009 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:Last 7 Days • Portions of southwestern Ethiopia received beneficial rains, while light rains sustained moisture deficits over parts of south central Ethiopia and areas in southern Kenya. • Moisture surpluses remained steady in most areas in the Gulf of Guinea region.

4. Rainfall Patterns: Last 7 Days During the past week, light to moderate rains fell over local areas in southwestern Kenya. However, rainfall deficits continued to increase over most areas in the central part of this country. Light rains also sustained moisture deficits over portions of southern Ethiopia. However, heavy rains soaked the western sector. Most areas in central Africa and the Gulf of Guinea region received beneficial rains. Seasonable dryness prevailed over the Sahel.

5. Rainfall Patterns: Last 30 Days During the last 30 days, rainfall was below average over most areas in central Kenya, parts of southern Ethiopia, and local areas in southern Uganda. Light rains sustained moisture deficits over much of southern DRC, northern Angola, and portions of northern Gabon. Moderate to heavy rains persisted in the Gulf of Guinea region in West Africa, resulting in moisture surpluses in the southern areas of Nigeria, Benin, and Togo.

6. Rainfall Patterns: Last 90 Days During the past 90 days, rainfall was above average over northern Namibia and southern Angola. In contrast, rainfall was below average over across much of Zimbabwe, central and southern Mozambique, and western Madagascar. Rainfall was above average over local areas in Tanzania. Further to the north below average rainfall persisted over central Ethiopia, and parts of western Kenya. Rainfall was above average locally over southeastern CAR, northern Congo, and coastal Cameroon.

7. Rainfall Patterns: Last 180 Days Over the past 180 days, rainfall was above average across most areas in continental southern Africa and along the east coast of Madagascar. Rainfall was below average along the northwest coast of Madagascar, northern Angola, southern and central DRC. Rainfall was also below average over most areas in Kenya. In central Africa, rainfall was above average over northern Congo, coastal Cameroon, and parts of the Gulf of Guinea region in West Africa.

8. Recent Rainfall Evolution Daily rainfall evolution during the last 90 days shows that rainfall continued to increase in the Gulf of Guinea region in West Africa (bottom left). Light rains sustained moisture deficits over southern Kenya (bottom right). Light rains persisted over parts of southern Ethiopia and sustained moisture deficits in this area (top right).

9. Atmospheric Circulation:Last 7 Days Over the past 7 days, the 850 hPa wind anomaly (left panel) featured an anomalous low level anticyclonic circulation centered over the subtropical north Atlantic. Westerly wind anomalies are evident off the Gulf of Guinea coast. The 200 hPa wind anomaly (right panel) featured two anticlyconic couplets across northern Africa. Westerly wind anomalies extended from the coast of South America across southern Africa into the Indian Ocean.

10. NCEP GEFS Model ForecastsNon-Bias Corrected Probability of precipitation exceedance Week-1: Valid 5 - 11 May, 2009Week-2: Valid 12 - 18 May, 2009 For week-1, the global ensemble forecast system (GEFS) suggests over 90% chance for precipitation to exceed 50 mm along coastal Gulf of Guinea, including Congo, Gabon, Cameroon, and from Nigeria to Liberia. For week-2 the highest chance for precipitation to exceed 50 mm is confined to northern DRC, southern Congo, and Gabon.

11. Experimental Week-1 & Week-2 Precipitation Outlooks Week-1 Outlook 5 - 11 May, 2009 Week-2 Outlook 12 – 18 May 2009 • An increased chance for above average rainfall over parts of the Gulf of Guinea and central Africa. Convergence of anomalous westerlies from eastern Atlantic and easterlies from the Indian Ocean turning into northeasterlies and the associated MJO related convection over Africa are expected to enhance precipitation in the region. • Confidence: Moderate • An increased chance for above average rainfall over parts of Cameroon, Gabon, DRC, and CAR. The projected MJO is expected to enhance precipitation in the region. • Confidence: Moderate

12. Summary • During the past week, light to moderate rains fell over local areas in southwestern Kenya. However, rainfall deficits continued to increase over most areas in the central part of this country. Light rains also sustained moisture deficits over portions of southern Ethiopia. However, heavy rains soaked the western sector. Most areas in central Africa and the Gulf of Guinea region received beneficial. Seasonable dryness prevailed over the Sahel. • During the last 30 days, rainfall was below average over most areas in central Kenya, parts of southern Ethiopia, and local areas in southern Uganda. Light rains sustained moisture deficits over much of southern DRC, northern Angola, and portions of northern Gabon. Moderate to heavy rains persisted in the Gulf of Guinea region in West Africa, resulting in moisture surpluses in the southern areas of Nigeria, Benin, and Togo. • For week1 valid 28 April – 4 May 2009, there is an increased chance for above average rainfall over Gabon, parts of Congo, southern Cameroon and western DRC. There is also an increased chance for above average rainfall over parts of east African countries.