African Monsoon: Recent Evolution and Current Status

1. The African Monsoon Recent Evolution and Current StatusInclude Week-1 and Week-2 Outlooks Update prepared by Climate Prediction Center / NCEP 9 July 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 • Weekly rainfall surpluses exceeded 100mm across eastern Sudan and western Ethiopia. • Week-1 outlooks call for an increased chance for above-average rainfall across many places in the Sahel and northern Gulf of Guinea countries, and western Ethiopia. In contrast, there is an increased chance for below-average rainfall over northeastern DRC, and parts of southern CAR and southern South Sudan.

4. Rainfall Patterns: Last 7 Days During the past 7 days, weekly rainfall totals exceeded 100mm over eastern Guinea-Conakry and northwestern Côte d’Ivoire, as well as eastern Sudan and western Ethiopia. Above-average rainfall was observed over the south half of Senegal, Mali, Guinea-Bissau, southern Mauritania, Ghana, southern Togo, northern Benin, southern Niger, much of Nigeria, southern, and western Central African Republic. Sierra Leone, parts of Liberia and Côte d’Ivoire, northeastern Nigeria, northern Central African Republic, northern DRC, parts of South Sudan and southern Ethiopia received below-average rainfall.

5. Rainfall Patterns: Last 30 Days During the past 30 days, below-average rainfall was observed over local areas in Sierra Leone, Liberia, northern Ghana, southeastern Burkina Faso, northeastern Nigeria, local areas in southwestern Cameroon, Equatorial Guinea, parts of Central African Republic. Below-average rainfall was also observed over northeastern DRC, southeastern South Sudan, parts of Uganda and southwestern Ethiopia. Rainfall was above-average over Mali, Guinea-Conakry, Côte d’Ivoire, much of Burkina Faso, Ghana, Togo, Benin, Niger, many parts of Nigeria, Cameroon, Chad, Congo-Brazzaville, western and eastern Central African Republic, western DRC, southern and eastern Sudan, portions of South Sudan, western Eritrea, and portions of Ethiopia.

6. Rainfall Patterns: Last 90 Days During the past 90 days, southern Mali, eastern Guinea-Conakry, Côte d’Ivoire, much of Burkina Faso, many parts of Ghana, northern Togo and Benin, northern Niger, Chad, many parts of Nigeria, Central African Republic, portions of Congo-Brazzaville, many parts of DRC, many places in the Greater Horn of Africa, Angola, northern Zambia, Mozambique and local areas in Namibia, South Africa and southern Botswana received above-average rainfall. Rainfall was below-average over much of Senegal, The Gambia, Guinea-Bissau, eastern Guinea-Conakry, Sierra Leone, parts of Ghana, Togo and Benin, eastern Burkina Faso, portions of Nigeria, Gabon, pats of Congo-Brazzaville, local areas in DRC, northeastern Ethiopia, eastern Eritrea and Madagascar.

7. Rainfall Patterns: Last 180 Days During the past 180 days, rainfall was above-average over eastern Guinea-Conakry, many parts of Mali, northern Sierra Leone, northern Liberia, much of Cote d’Ivoire, Burkina Faso, parts of Ghana, Togo and Benin, parts of Nigeria, central and southern chad, CAR, southern Sudan, much of South Sudan, many parts of Ethiopia, southern Somalia, much of Kenya and Tanzania, Rwanda, Burundi, much of Uganda, Equatorial-Guinea, portions of Congo-Brazzaville, parts of DRC and Angola, Zambia, South Africa, northern Namibia, many parts of Botswana and Mozambique, northern Malawi, much of Zimbabwe, and northern and eastern Madagascar. Below-average rainfall was observed over the far western West Africa, southern sierra Leone and Liberia, parts of Ghana, eastern Burkina Faso, parts of Nigeria, Gabon, portions of DRC and Angola, northeastern Ethiopia, many parts of Namibia, central and southern Botswana, local areas in South Africa and Mozambique, and western and southern Madagascar.

8. Recent Rainfall Evolution Daily evolution of rainfall over the last 90 days at selected locations shows that seasonal rainfall totals remain below-average over parts of eastern Burkina Faso (bottom left). Moderate to locally heavy rainfall sustained moisture surpluses over parts of Chad (bottom right) and eastern Sudan (top right).

9. Atmospheric Circulation:Last 7 Days A broad area of anomalous lower-level cyclonic shear (left) and upper-level divergence across West and Central Africa may have contributed to observed above-average rainfall in the region.

10. NCEP GEFS Model ForecastsNon-Bias Corrected Probability of precipitation exceedance Week-1: Valid 10 – 16 July, 2018 Week-2: Valid 17 – 23 July, 2018 For week-1 (left panel), there is an increased chance for weekly rainfall totals to exceed 50 mm across southwestern Guinea, Sierra Leone and western Liberia, as well as local areas in Cameroon and Nigeria, and western Ethiopia. For week 2 (right panel) , there is an increased chance for rainfall totals to exceed 50 mm across Guinea, Sierra Leone, south Mali, Burkina Faso, south Niger, north Nigeria, local areas over Chad and Cameroon, western Eritrea and western Ethiopia.

11. Week-1 Precipitation Outlooks 10 - 16 July, 2018 • There is an increased chance for above-average rainfall across portions of Senegal, Gambia, Guinea-Bissau, Guinea-Conakry, Sierra Leone, southern Mali, Liberia, Northern Côte d’Ivoire, Burkina Faso, southwestern Niger, Togo, Benin, Nigeria: Stronger than normal monsoon flow across West Africa, coupled with an area anomalous lower-level convergence and upper-level divergence is expected to enhance rainfall in the region. Confidence: Moderate • There is an increased chance for below-average rainfall over northern Congo-Brazzaville, northern DRC, and western CAR: 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 eastern Sudan, western Ethiopia and, Eritrea: 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 17 - 23 July, 2018 • There is an increased chance for above-average rainfall over Guinea-Conakry, Sierra Leone and parts of Liberia: An area 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 northern Nigeria, Cameroon and southern Chad: An area of anomalous lower-level convergence and upper-level divergence is expected to enhance rainfall in the region. Confidence: Moderate

13. Summary During the past 7 days, weekly rainfall totals exceeded 100mm over eastern Guinea-Conakry and northwestern Côte d’Ivoire, as well as eastern Sudan and western Ethiopia. Above-average rainfall was observed over the south half of Senegal, Mali, Guinea-Bissau, southern Mauritania, Ghana, southern Togo, northern Benin, southern Niger, much of Nigeria, southern, and western Central African Republic. Sierra Leone, parts of Liberia and Côte d’Ivoire, northeastern Nigeria, northern Central African Republic, northern DRC, parts of South Sudan and southern Ethiopia received below-average rainfall. During the past 30 days, below-average rainfall was observed over local areas in Sierra Leone, Liberia, northern Ghana, southeastern Burkina Faso, northeastern Nigeria, local areas in southwestern Cameroon, Equatorial Guinea, parts of Central African Republic. Below-average rainfall was also observed over northeastern DRC, southeastern South Sudan, parts of Uganda and southwestern Ethiopia. Rainfall was above-average over Mali, Guinea-Conakry, Côte d’Ivoire, much of Burkina Faso, Ghana, Togo, Benin, Niger, many parts of Nigeria, Cameroon, Chad, Congo-Brazzaville, western and eastern Central African Republic, western DRC, southern and eastern Sudan, portions of South Sudan, western Eritrea, and portions of Ethiopia. During the past 90 days, southern Mali, eastern Guinea-Conakry, Côte d’Ivoire, much of Burkina Faso, many parts of Ghana, northern Togo and Benin, northern Niger, Chad, many parts of Nigeria, Central African Republic, portions of Congo-Brazzaville, many parts of DRC, many places in the Greater Horn of Africa, Angola, northern Zambia, Mozambique and local areas in Namibia, South Africa and southern Botswana received above-average rainfall. Rainfall was below-average over much of Senegal, The Gambia, Guinea-Bissau, eastern Guinea-Conakry, Sierra Leone, parts of Ghana, Togo and Benin, eastern Burkina Faso, portions of Nigeria, Gabon, pats of Congo-Brazzaville, local areas in DRC, northeastern Ethiopia, eastern Eritrea and Madagascar. Week-1 outlooks call for an increased chance for above-average rainfall across many places in the Sahel and northern Gulf of Guinea countries, and western Ethiopia. In contrast, there is an increased chance for below-average rainfall over northeastern DRC, and parts of southern CAR and southern South Sudan.