The African Monsoon Recent Evolution and Current Status

1. The African Monsoon Recent Evolution and Current Status Update prepared by Climate Prediction Center / NCEP 21 JUNE 2010 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 • During the past seven days, extremely heavy rains may have resulted in flooding in local areas in southern Cote d’Ivoire. • Rainfall continued to be significantly below average over southeastern Nigeria.

4. Rainfall Patterns: Last 7 Days During the past seven days, moderate to heavy downpours soaked Cote d’Ivoire and the southern areas of Ghana to sustain moisture surpluses in this region. The rains were locally extremely heavy and may have resulted in flooding especially in southern Cote d’Ivoire. Lighter rains fell in Guinea, Sierra Leone, and Liberia. Rainfall was also below average over the central areas of Togo and Benin, while moisture deficits persisted in southeastern Nigeria and western Cameroon. In central Africa, rainfall was above average over the northern areas of DRC, Congo, and CAR. Seasonably dry weather prevailed over eastern and southern Africa.

5. Rainfall Patterns: Last 30 Days During the past 30 days, rainfall was above average along portions of coastal Gulf of Guinea and most parts of Burkina Faso and southern Mali. Rainfall was below average over parts of southern and central Nigeria, as well as coastal central Africa. Rainfall was above average over southern Chad, CAR and the northern areas of Congo and DRC. In east Africa, rainfall was above average over western Ethiopia, while moisture surpluses persisted in the southern parts of Madagascar.

6. Rainfall Patterns: Last 90 Days During the past 90 days, southeastern Guinea, Liberia, and coastal areas of Cote d’Ivoire experienced above average rainfall. However, rainfall was below average over parts of Nigeria. Rainfall was above average over the northern areas of central Africa and parts of the Greater Horn of Africa. Rainfall was below average over southeastern DRC, Tanzania, and along the east coast of Madagascar. The central areas of southern Africa maintained above average rainfall.

7. Rainfall Patterns: Last 180 Days During the past 180 days, rainfall was above average along the western Gulf of Guinea coastline, much of central and eastern Africa, and parts of southern Africa. However, Central Mozambique, western, central and the northern tip of Madagascar had below average rainfall.

8. Recent Rainfall Evolution Daily evolution of precipitation during the last 90 days at selected regions indicates a good start to the rainy season in several locations in the Gulf of Guinea (lower panel – left). Despite steady rainfall, seasonal average has been below average over central Nigeria (lower panel – right). Steady rains maintained soil wetness in western Ethiopia (upper panel – right).

9. Atmospheric Circulation:Last 7 Days The 850 hPa wind anomaly (left panel) reflected westerly wind anomalies across the tropical eastern Atlantic. A strengthening of the Somali Jet as indicated with southerly wind anomalies over the western Indian Ocean was evident. The 200 hPa wind anomaly (right panel) featured an upper level trough centered over Asia coupled with an anomalous cyclonic circulation centered over southern Europe.

10. NCEP GEFS Model ForecastsNon-Bias Corrected Probability of precipitation exceedance Week-1: Valid 22 - 28 June, 2010Week-2: Valid 29 June – 5 July, 2010 For week-1, there is a high chance for precipitation to exceed 50 mm along the coast line of the Gulf of Guinea. For week-2, there is a high chance for precipitation to exceed 50 mm in most parts of Guinea, southern Nigeria, and the southern half of Cameroon. There is also a high chance for precipitation to exceed 50 mm over western Ethiopia.

11. Experimental Week-1 Precipitation Outlooks Week-1 Outlook 22 – 28 June, 2010 • There is an increased chance for above average precipitation along the Gulf of Guinea coast: The anomalous moist winds from the Atlantic Ocean are expected to converge along the coastal areas and enhance rainfall in the region. • Confidence: Moderate • 2. There is an increased chance for below average rainfall over parts of southern Sudan:An anomalous lower tropospheric divergence flow is expected to suppress rainfall in the region. Confidence: Moderate

12. Experimental Week-2 Precipitation Outlooks Week-2 Outlook 29 June – 5 July, 2010 No forecast – Climatology suggested.

13. Summary During the past seven days, moderate to heavy downpours soaked Cote d’Ivoire and the southern areas of Ghana to sustain moisture surpluses in this region. The rains were locally extremely heavy and may have resulted in flooding especially in southern Cote d’Ivoire. Lighter rains fell in Guinea, Sierra Leone, and Liberia. Rainfall was also below average over the central areas of Togo and Benin, while moisture deficits persisted in southeastern Nigeria and western Cameroon. In central Africa, rainfall was above average over the northern areas of DRC, Congo, and CAR. Seasonably dry weather prevailed over eastern and southern Africa. During the past 30 days, rainfall was above average along portions of coastal Gulf of Guinea and most parts of Burkina Faso and southern Mali. Rainfall was below average over parts of southern and central Nigeria, as well as coastal central Africa. Rainfall was above average over southern Chad, CAR and the northern areas of Congo and DRC. In east Africa, rainfall was above average over western Ethiopia, while moisture surpluses persisted in the southern parts of Madagascar. During the past 90 days, southeastern Guinea, Liberia, and coastal areas of Cote d’Ivoire experienced above average rainfall. However, rainfall was below average over parts of Nigeria. Rainfall was above average over the northern areas of central Africa and parts of the Greater Horn of Africa. Rainfall was below average over southeastern DRC, Tanzania, and along the east coast of Madagascar. The central areas of southern Africa maintained above average rainfall. For week-1, there is an increased chance for above average precipitation along the Gulf of Guinea coast. There is an increased chance for below average rainfall over parts of southern Sudan.