The African Monsoon Recent Evolution and Current Status

1. The African Monsoon Recent Evolution and Current Status Update prepared by Climate Prediction Center / NCEP 27 October 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 • Experimental Week-1 and Week-2 Outlooks • Summary

3. Highlights:Last 7 Days • During the past 7 days, moderate to heavy rains soaked parts of the Greater Horn of Africa, including western Kenya, Uganda, southern Sudan, and northwestern Tanzania. • Rainfall continued to linger over pockets in the Sahel, while parts of the eastern sector of the Gulf of Guinea region received less than average rainfall.

4. Rainfall Patterns: Last 180 Days Over the past 180 days, rainfall was above average over most areas in West Africa and central Africa. In the east, rainfall was below average in central Sudan , and in pockets over southwestern Kenya and southern Somalia. Rainfall was above average over western Ethiopia.

5. Rainfall Patterns: Last 90 Days Over the past 90 days, rainfall was above average over most areas in the western part of the Sahel and most areas in the Gulf of Guinea region and parts of central Africa. Rainfall was below average central Sudan, and above average in the south and in western Ethiopia.

6. Rainfall Patterns: Last 30 Days Over the last 30 days, rainfall was above average over pockets in the West Africa and central Africa. In the east, rainfall was above average in western Kenya and in the western part of Ethiopia. Rainfall was slightly below average over eastern South Africa.

7. Rainfall Patterns: Last 7 Days During the past 7 days, rainfall was below average in parts of the Gulf of Guinea region, while sectors in East Africa, including Kenya and Uganda received above average rains. The southern sector of Somalia registered below average rainfall.

8. Recent Rainfall Evolution Over the last 30 days, rainfall continued to be above average over the western part of the Sahel (bottom panel – left). Rainfall was also above average over portions of eastern Africa (bottom panel – right). Rainfall was below average over western Ethiopia (upper panel – right).

9. Atmospheric Circulation:Last 7 Days Over the past 7 days, the 850 hPa wind anomaly (left panel) featured weak westerly anomalies in the Gulf of Guinea with on-shore flow into Nigeria and a band of northerlies over the central portion of north Africa. Also featured is a cyclonic circulation over the central Indian Ocean. The 200hpa wind anomaly featured a westerly anomaly over the Equatorial Atlantic and a weak easterly anomaly over western Indian Ocean into Eastern Africa.

10. Weekly Precipitation Climatology Based on CPC daily precipitation analysis for the period 1979-present, much of the rainfall in Africa during the periods 28 Oct – 3 Nov and 4-10 Nov occurs In central Africa in the Congo Basin, and in the Greater Horn of Africa in the areas encompassing Kenya, northwestern Tanzania, Uganda, and southern Sudan.

11. NCEP GEFS Model ForecastsNon-Bias Corrected Probability of precipitation exceedance Week-1: Valid 28 October – 3 November, 2008Week-2: Valid 4 - 10 November, 2008 For week-1, the global ensemble forecast system (GEFS) suggests 90% chance for precipitation to be above average over portions of central Africa, including northern DRC, Congo, and Gabon. There is a 90% chance or above for precipitation to exceed 50 mm over parts of Ethiopia. For week-2, there is a high chance for precipitation to exceed 50 mm over the eastern half of DRC, parts of Congo, and Gabon. Note: The GFS tends to suppress (increase) precipitation in the Sahel (Gulf of Guinea region).

12. Experimental Week-1 & Week-2 Precipitation Outlook Week-1 Outlook Valid 2 October – 3 November, 2008 Climatology is expected across the Congo Basin and the Greater Horn of Africa: The active phase of the MJO currently centered over the western Pacific far away from Africa, and conflicting local signals including moisture convergence in the Congo basin will increase the chance for average rainfall in central Africa and in the Greater Horn of Africa (see slide # 11). Week-2 Outlook Valid 4-10 November, 2008 Climatology is expected across the Congo Basin and the Greater Horn of Africa: The active phase of the MJO currently centered over the western Pacific far away from Africa, and conflicting local signals including moisture convergence in the Congo basin will increase the chance for average rainfall in central Africa and in the Greater Horn of Africa (see slide # 11).

13. Summary • During the past 7 days, portions of West Africa, including the western and central sectors of the Sahel continued to register moderate to heavy rains. The late rains can be damaging to already harvested crops but kept on the ground. In contrast, rainfall was below average over the eastern part of the Gulf of Guinea region. Light to moderate rains fell over much of the central African rains. Much of Cameroon, CAR, and the northern areas of Gabon, Congo, and DRC received below average rainfall, wile southwestern DRC, central and southern Congo, and eastern Gabon received above average rainfall. The eastern sector of the Greater Horn of Africa, including southern Sudan, Uganda, and western Kenya received beneficial rains as totals average 15 to 50 mm above the mean. The southern part of Somalia received below average rainfall. • Over the last 30 days, the recent rains sustained moisture surpluses over portions of western East Africa, including western Kenya, parts of the Lake Victoria Basin, and southern Sudan. Rainfall also continued to be above average over pockets in the western part of the Sahel, including southeastern Senegal and western Mali. • For the week1 ending 27 October , there is an increased chance for above average rainfall over the Congo Basin. For week2 climatologyis expected.