The African Monsoon Recent Evolution and Current Status

1. The African Monsoon Recent Evolution and Current Status Update prepared by Climate Prediction Center / NCEP 02 June 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 Outlook • Summary

3. Highlights:Last 7 Days • Light or no rain fell in the southern areas of the Sahel as the rainy season is generally off to a slow start in this subregion. • Beneficial rains fell in eastern parts of the Gulf of Guinea region. • Near average rains fell in western Ethiopia and in the regions adjacent to Lake Victoria.

4. Rainfall Patterns: Last 180 Days Over the past 180 days, rainfall was below average over most areas in the Gulf of Guinea region, central Africa, and parts of the Greater Horn of Africa. Rainfall was above average over portions of Tanzania and in parts of southern Africa, except for northern and eastern Madagascar, and locally the southern areas of Zimbabwe and Mozambique.

5. Rainfall Patterns: Last 90 Days Over the past 90 days, rainfall was below average over most areas in the Gulf of Guinea region, central Africa, and parts of the Greater Horn of Africa. Rainfall was above average in local areas in southern Africa.

6. Rainfall Patterns: Last 30 Days Over the last 30 days, rainfall was below average over most of Ethiopia, Kenya, Uganda, northwestern Tanzania, Rwanda, and Burundi. Rainfall was also below average over portions of central Africa and along portions of the Gulf of Guinea coast.

7. Rainfall Patterns: Last 7 Days During the past 7 days, rainfall was near average across most crop areas in Africa, except in local areas along the Guinean coast and in central Kenya and southwester Ethiopia, where rainfall was slightly below average.

8. Recent Rainfall Evolution Moisture deficits persisted in portions of the northern Horn of Africa (top panel - right); Western Kenya and Uganda continued to register below average rainfall (bottom panel – right); Below average rains also sustained moisture deficits over parts of the Gulf of Guinea region (bottom panel – left).

9. Atmospheric Circulation:Last 7 Days Over the past 7 days, the 850 hPa wind anomaly (left panel) featured a westerly wind anomalies in the eastern Atlantic north of the equator. Easterly wind anomalies are evident in the central Indian Ocean. The 200 hPa wind anomaly (right panel) features a northeasterly flow across northern Africa feeding into strong westerlies in the Indian Ocean south of the equator.

10. Rainfall Climatology: 27 May-2June Rainfall totals for the week 27 May – 2 June range between 15 and 45 mm over the Gulf of Guinea region, extending north into the southern areas of the Sahel, western Ethiopia, southwestern Kenya, eastern Uganda, and along coastal Kenya and northeast Tanzania.

11. NCEP GEFS Model ForecastsNon-Bias Corrected Probability of precipitation exceedance – Week-1Valid 3 June - 9 June, 2008 NCEP global ensemble forecast system (GEFS) suggests a high tilt in the odds (90% or above) for precipitation to exceed 25 mm along the Guinean coast, as well as coastal Kenya and northeastern Tanzania, the western Ethiopian highlands, and northern central Africa (left panel). Areas with the highest chance for precipitation to exceed 50 mm (right panel) include western Ethiopia, northeast DRC, Cameroon, and sections along coastal Gulf of Guinea.

12. Experimental Week-1 Precipitation OutlookValid 27 May - 2 June, 2008 • An increased chance for above average • rainfall along the Guinean coastline, from Liberia to • Nigeria: The enhanced phase of the MJO, a low pressure, • System and the low level moisture advection from the Gulf • of Guinea are expected to enhance rainfall in this region. • Confidence: High • 2. An increased chance for above average • rainfall over western Ethiopia: The active phase of the • MJO is expected to enhance precipitation in this area. • Confidence: Moderate • 3. An increased chance for above average • rainfall along the coasts of northern Kenya and • southern Somalia: Low level moisture advection from the • western Indian ocean is expected to enhance precipitation • in this area. • Confidence: Moderate

13. Summary • Over the past 7 days, light to moderate rains fell over parts of the Gulf of Guinea region, including eastern Cote d’Ivoire, Ghana, Togo, and Benin. Light or no rain fell in the southern areas of the Sahel, as the rainy season is off to a slow start in this region. Rainfall was below average over portions of Burkina Faso. In central Africa, rainfall was lighter than average over CAR, northern Congo, and in local areas in northern DRC. In the Greater Horn of Africa, rainfall was below average in southwestern Ethiopia and central Kenya, while eastern Uganda and the area in the vicinity of Lake Victoria received above average rainfall. Generally, seasonably dry weather prevailed in southern Africa. • Cumulative rainfall over many areas in the Gulf of Guinea region over the past 30 and 90 days remain below average. The areas most severely affected include western Cote d’Ivoire, which registered only 50% of the cumulative 90-day rainfall totals. As the rainy season begins to wind down in many parts of the Greater Horn of Africa, Parts of the region are likely to end the season with significant moisture deficits. Parts of Kenya, Uganda, and Ethiopia registered only a little bit more than 50% of the cumulative 90-day total rainfall. • For the period 3 June – 9 June 2008, there is an increased chance for above average rainfall along the Guinean coastline, northern central Africa, southwestern Ethiopia, and along the coastal boundary between Kenya and Somalia.