The African Monsoon Recent Evolution and Current Status

1. The African Monsoon Recent Evolution and Current Status Update prepared by Climate Prediction Center / NCEP 30 March 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 • Tropical Cyclone Izilda made land fall in southern Madagascar (26 March) and caused local flooding in some localities. The heavy rains associated with the storm increased the 90-day moisture surplus in this region. • Rainfall was significantly below average over parts of southern and central Africa.

4. Rainfall Patterns: Last 180 Days Over the past 180 days, rainfall was near or above average across most areas in continental southern Africa. Rainfall enhancement was greatest in northern Namibia and southern Angola. However, northern Angola and southern DRC, as well as northern Madagascar received below average rainfall. Areas in central Africa, including Gabon, local areas in central Congo, and southern Kenya also received below average rainfall. Rainfall was slightly above average along the Guinea coast over West Africa.

5. Rainfall Patterns: Last 90 Days During the past 90 days, rainfall was above average over most areas in continental southern Africa. The largest moisture surpluses occurred over northwestern Namibia. In contrast, rainfall was below average over most areas in northern Madagascar and along coastal Mozambique. Rainfall was also below average over eastern Tanzania, most areas in Kenya, and the western half of DRC southward into northern Angola. Rainfall was slightly above average in local areas along the Guinea coast.

6. Rainfall Patterns: Last 30 Days During the last 30 days, rainfall was above average over parts of southern Africa, including northern Botswana, Zambia, the area along the border between DRC and Tanzania. Tropical Cyclone Izilda contributed to the excessive rains in southern Madagascar. In contrast, rainfall was below average over parts of the Greater Horn of Africa, including northern Tanzania, southwestern Kenya, eastern Uganda, and south central Ethiopia. Rainfall was above average in local areas in the Gulf of Guinea region.

7. Rainfall Patterns: Last 7 Days During the past week, rainfall diminished significantly over southern Africa as the ITCZ began its northward migration. Light or no rain resulted in moisture deficits over southern Angola, western Zambia, southern DRC, and locally along the northern coast of Mozambique. Tropical Cyclone Izilda brought heavy rains to the southern areas of Madagascar. Further to the north, local areas along the Guinean coast and in southwestern Ethiopia registered above average rainfall.

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). Tropical Cyclone Izilda increased moisture surpluses over southern Madagascar (bottom right). Episodic heavy rainfall did not help erase the 90-day moisture deficits over southwestern Ethiopia (top right).

9. Atmospheric Circulation:Last 7 Days Over the past 7 days, the 850 hPa wind anomaly (left panel) featured a low level cyclonic circulation centered over the Mozambique Channel reflecting the presence of tropical cyclone Izilda. Easterly wind anomalies prevailed over central Africa. The 200 hPa wind anomaly (right panel) featured anomalous upper level divergence over southwest Indian Ocean.

10. NCEP GEFS Model ForecastsNon-Bias Corrected Probability of precipitation exceedance Week-1: Valid 31 March – 6 April, 2009Week-2: Valid 7-13 April, 2009 For week-1, the global ensemble forecast system (GEFS) suggests over 90% chance for precipitation to exceed 50 mm along the eastern boundary of DRC and over the Mozambique Channel northwest of Madagascar. For week-2, the model exhibits a chance for precipitation to exceed 50 mm over central Africa off the Atlantic coast.

11. Experimental Week-1 & Week-2 Precipitation Outlooks Week-1 Outlook Valid 31 March – 6 April, 2009 Week-2 Outlook Valid 7 –13 April, 2009 • An increased chance for above average rainfall over parts of Central Africa and along the Guinea coast: The active phase of the MJO over Africa is expected to enhance precipitation in this region. • Confidence: Moderate • An increased chance for above average rainfall over parts of Central Africa: The active phase of the MJO over Africa is expected to enhance precipitation in this region. • Confidence: Moderate

12. Summary • During the past week, rainfall diminished significantly over southern Africa as the ITCZ began its northward migration. Light or no rain resulted in moisture deficits over southern Angola, western Zambia, southern DRC, and locally along the northern coast of Mozambique. Tropical Cyclone Izilda brought heavy rains to the southern areas of Madagascar. Further to the north, local areas along the Guinean coast and in southwestern Ethiopia registered above average rainfall. • During the last 30 days, rainfall was above average over parts of southern Africa, including northern Botswana, Zambia, the area along the border between DRC and Tanzania. Tropical Cyclone Izilda contributed to the excessive rains in southern Madagascar. In contrast, rainfall was below average over parts of the Greater Horn of Africa, including northern Tanzania, southwestern Kenya, eastern Uganda, and south central Ethiopia. Rainfall was above average in local areas in the Gulf of Guinea region. • The active phase of the Madden Julian Oscillation (MJO) over Africa during week1 and week2 is expected to result in above average rainfall over parts of Central Africa and along the Guinea coast. For week2, the area of above average precipitation is expected to shift east and to include parts of southern Sudan, Uganda, and southwestern Ethiopia.