The African Monsoon Recent Evolution and Current Status Include Week-1 and Week-2 Outlooks

1. The African Monsoon Recent Evolution and Current StatusInclude Week-1 and Week-2 Outlooks Update prepared by Climate Prediction Center / NCEP 21 May 2018 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 • Rainfall was below-average over many places in the Gulf of Guinea countries. • Above-average rainfall was observed across portions of central and eastern Africa. • Week-1 outlooks call for an increased chance for above-average rainfall over parts of Nigeria, Cameroon, Chad, CAR, parts of eastern DRC, Burundi, Rwanda, Uganda, South Sudan, Kenya, and Ethiopia. In contrast, there is an increased chance for below-average rainfall over parts of Guinea, Sierra Leone, Liberia , Cote d'Ivoire, Ghana, and southern Mali.

4. Rainfall Patterns: Last 7 Days During the past seven days, rainfall was below-average over much of Guinea-Conakry, Sierra Leone, Liberia, Cote d’Ivoire, parts of Burkina Faso and Ghana, Togo, Benin, much of Nigeria, western and central Cameroon, parts of Gabon, southern Congo-Brazzaville, local areas in DRC and Uganda, and northwestern Ethiopia. In contrast, local areas in northern Ghana, Togo and Benin, southeastern Cameroon, parts of CAR, northern Congo-Brazzaville, northern Angola, many parts of DRC, parts of South Sudan, southwestern Ethiopia, parts of Kenya, northern Uganda, and portions of Tanzania received above-average rainfall.

5. Rainfall Patterns: Last 30 Days During the past 30 days, much of Guinea-Conakry, Sierra Leone, Liberia, southern Mali, southern Cote d’Ivoire, Burkina Faso, northern Ghana, parts of Togo and Benin, portions of Nigeria, southern Cameroon, parts of Gabon, local areas in South Sudan, and portions of Ethiopia and northern Somalia had below-average rainfall. In contrast, central and northern Cote d’Ivoire, southern Ghana, portions of Nigeria, local areas in Cameroon, much of CAR, northern Gabon, northern Angola, DRC, Rwanda, Burundi, parts of Uganda and South Sudan, southern and western Kenya, parts of Ethiopia, southern Somalia, and local areas in Tanzania had above-average rainfall.

6. Rainfall Patterns: Last 90 Days During the past 90 days, above-average rainfall was observed over northern Sierra Leone, parts of Liberia, eastern Guinea Conakry, much of Cote d’Ivoire, parts of Ghana, southwestern Burkina Faso, Togo, Benin, portions of Nigeria, much of Cameroon, CAR, South Sudan, much of Congo-Brazzaville, many parts of DRC, portions of Angola, western and southern Ethiopia, Kenya, Uganda, Somalia, Tanzania, Zambia, much of Zimbabwe, Botswana, many parts of Mozambique and South Africa, and northwestern Madagascar. In contrast, rainfall was below-average over much of Guinea, southern Mali, southern Sierra Leone and southern Liberia, local areas in Nigeria, much of Gabon, local areas in Congo-Brazzaville, parts of Angola, local areas in DRC and Ethiopia, western and southern Namibia, parts of South Africa, and southern Madagascar.

7. Rainfall Patterns: Last 180 Days During the past 180 days, rainfall was above-average over local areas in Sierra Leone and Liberia, Cote d’Ivoire, southwestern Burkina Faso, parts of Ghana, Togo, Benin, Nigeria, Cameroon, Central African Republic (CAR), much of South Sudan, western and southern Ethiopia, parts of Somalia, much of Kenya and Tanzania, Rwanda, Burundi, Uganda, much of Congo-Brazzaville, Democratic Republic of Congo (DRC), parts of Angola, parts of Zambia, parts of South Africa, many parts of Mozambique, northern Botswana, much of Zimbabwe, and northern and eastern Madagascar. In contrast, below-average rainfall was observed over the far western West Africa, local areas in Ghana, and Nigeria, Gabon, portions of DRC and Angola, parts of northern and western Ethiopia, much of Namibia, Botswana, local areas in Mozambique, parts of and South Africa and southwestern Madagascar.

8. Recent Rainfall Evolution Daily evolution of rainfall over the last 90 days at selected locations shows that seasonal total rainfall remained below-normal over parts of Guinea (bottom left) and northern Angola (bottom right). In contrast, moderate to heavy rainfall sustained moisture surpluses over parts of Kenya (top right).

9. Atmospheric Circulation:Last 7 Days A broad area of anomalous lower-level southerly flow with its associated convergence prevailed across central Africa.

10. NCEP GEFS Model ForecastsNon-Bias Corrected Probability of precipitation exceedance Week-1: Valid 22 – 28 May, 2018 Week-2: Valid 29 May – 4 June, 2018 For week-1 (left panel) and week-2 (right panel), there is an increased chance for weekly rainfall totals to exceed 50mm over in the Lake Victoria region, portions of Ethiopia and Kenya, and local areas in Cameroon.

11. Week-1 Precipitation Outlooks 22 – 28 May, 2018 • There is an increased chance for below-average rainfall over parts of Guinea, Sierra Leone, Liberia , Cote d'Ivoire, Ghana, and southern Mali: An area of anomalous lower level divergence and upper-level convergence is expected to suppress rainfall in the region. Confidence: Moderate • There is an increased chance for above-average rainfall over parts of Nigeria, Cameroon, Chad, and CAR: An area of anomalous lower-level convergence and upper-level divergence is expected to enhance rainfall in the region. Confidence: Moderate • There is an increased chance for above-average rainfall over parts of eastern DRC, Burundi, Rwanda, Uganda, southern South Sudan, western Kenya, and western Ethiopia: An area of anomalous lower-level convergence and upper-level divergence is expected to enhance rainfall in the region. Confidence: Moderate

12. Week-2 Precipitation Outlooks 29 May – 4 June, 2018 • There is an increased chance for above-average rainfall over much of Nigeria, Cameroon, southern Chad, CAR, northern DRC, South Sudan, and western Ethiopia: A broad area of anomalous lower-level convergence and pockets northern DRC, South Sudan, Sudan and Ethiopia. Confidence: Moderate

13. Summary • During the past seven days, rainfall was below-average over much of Guinea-Conakry, Sierra Leone, Liberia, Cote d’Ivoire, parts of Burkina Faso and Ghana, Togo, Benin, much of Nigeria, western and central Cameroon, parts of Gabon, southern Congo-Brazzaville, local areas in DRC and Uganda, and northwestern Ethiopia. In contrast, local areas in northern Ghana, Togo and Benin, southeastern Cameroon, parts of CAR, northern Congo-Brazzaville, northern Angola, many parts of DRC, parts of South Sudan, southwestern Ethiopia, parts of Kenya, northern Uganda, and portions of Tanzania received above-average rainfall. • During the past 30 days, much of Guinea-Conakry, Sierra Leone, Liberia, southern Mali, southern Cote d’Ivoire, Burkina Faso, northern Ghana, parts of Togo and Benin, portions of Nigeria, southern Cameroon, parts of Gabon, local areas in South Sudan, and portions of Ethiopia and northern Somalia had below-average rainfall. In contrast, central and northern Cote d’Ivoire, southern Ghana, portions of Nigeria, local areas in Cameroon, much of CAR, northern Gabon, northern Angola, DRC, Rwanda, Burundi, parts of Uganda and South Sudan, southern and western Kenya, parts of Ethiopia, southern Somalia, and local areas in Tanzania had above-average rainfall. • During the past 90 days, above-average rainfall was observed over northern Sierra Leone, parts of Liberia, eastern Guinea Conakry, much of Cote d’Ivoire, parts of Ghana, southwestern Burkina Faso, Togo, Benin, portions of Nigeria, much of Cameroon, CAR, South Sudan, much of Congo-Brazzaville, many parts of DRC, portions of Angola, western and southern Ethiopia, Kenya, Uganda, Somalia, Tanzania, Zambia, much of Zimbabwe, Botswana, many parts of Mozambique and South Africa, and northwestern Madagascar. In contrast, rainfall was below-average over much of Guinea, southern Mali, southern Sierra Leone and southern Liberia, local areas in Nigeria, much of Gabon, local areas in Congo-Brazzaville, parts of Angola, local areas in DRC and Ethiopia, western and southern Namibia, parts of South Africa, and southern Madagascar. • Week-1 outlooks call for an increased chance for above-average rainfall over parts of Nigeria, Cameroon, Chad, CAR, parts of eastern DRC, Burundi, Rwanda, Uganda, South Sudan, Kenya, and Ethiopia. In contrast, there is an increased chance for below-average rainfall over parts of Guinea, Sierra Leone, Liberia , Cote d'Ivoire, Ghana, and southern Mali.