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 9 April 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 over local areas in southern Ethiopia, western Tanzania, southern DRC and northwestern Zambia. • Rainfall was below-average over much of the Gulf of Guinea countries. • Week-1 outlooks call for an increased chance for above-average rainfall over Sierra Leone, Liberia, western and northern Angola, southern and eastern DRC, Rwanda, Burundi, western and southern Tanzania, southern Uganda, southwestern and northeastern Kenya, eastern and southern Ethiopia, portions of Somalia, Malawi, and northern Mozambique. In contrast, there is an increased chance for below-average rainfall over northern DRC, southern CAR and western South Sudan.

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

5. Rainfall Patterns: Last 30 Days During the past 30 days, eastern Guinea, parts of Cote d’Ivoire, western Burkina Faso, local areas in Ghana, parts of Togo and Benin, parts of southern Nigeria, Cameroon, CAR, South Sudan, Congo-Brazzaville and parts of DRC, southern and eastern Angola, northern Namibia, much of Tanzania, Uganda, Rwanda, Burundi and Kenya, South Sudan, parts of Ethiopia, local areas in southern Somalia, parts of Zambia, local areas in Malawi, parts of Botswana and Zimbabwe, portions of South Africa, local areas in Mozambique, and portions of Madagascar had above-average rainfall. In contrast, much of Gabon, parts of Angola and DRC, local areas in Zimbabwe, parts of Mozambique, and central and southern Madagascar had below-average rainfall.

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

7. Rainfall Patterns: Last 180 Days During the past 180 days, rainfall was above-average over Sierra Leone, Cote d’Ivoire, parts of Burkina Faso, southwestern Ghana, parts of Togo and Benin, Cameroon, Central African Republic (CAR), much of South Sudan, portions of Ethiopia, parts of Somalia, much of Kenya and Tanzania, Rwanda, Burundi, portions of Uganda, much of Congo-Brazzaville, portions of Democratic Republic of Congo (DRC), parts of Angola, much 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, eastern Ghana, many parts of Nigeria, southern Chad, Gabon, portions of DRC and Angola, northeastern Ethiopia, southeastern Kenya, local areas in Somalia, much of Namibia, local areas in Mozambique, and parts of 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-average over parts of northern Angola (bottom left), and northeastern Ethiopia (top right). In contrast, moderate to heavy rainfall sustained moisture surpluses over parts of Tanzania (bottom right).

9. Atmospheric Circulation:Last 7 Days At 700-hPa level (left), anomalous cross-equatorial flow prevailed near the Greater Horn of Africa.

10. NCEP GEFS Model ForecastsNon-Bias Corrected Probability of precipitation exceedance Week-1: Valid 10 – 16 Apr, 2018 Week-2: Valid 17 – 23 Apr, 2018 For week-1 (left panel) and week-2 (right panel), there is an increased chance for weekly rainfall totals to exceed 50mm over parts Angola, DRC, Rwanda, Burundi, Uganda, Kenya, Tanzania, Somalia, and portions of Ethiopia.

11. Week-1 Precipitation Outlooks • There is an increased chance for above-average rainfall over Sierra Leone and Liberia: 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 northern Angola, southern DRC, western Tanzania, Burundi, Rwanda, and southwestern Kenya: A broad area of anomalous lower-level convergence, coupled with upper-level divergence is expected to enhance rainfall in the region. Confidence: Moderate • There is an increased chance for below-average rainfall over southern CAR, northern DRC, and western South Sudan: An area of anomalous lower-level divergence, combined with upper-level convergence is expected to suppress rainfall in the region. Confidence: Moderate • There is an increased chance for above-average rainfall over eastern Zambia, Malawi, southern Tanzania, and northern Mozambique: Stronger than normal onshore flow, with its associated 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 Kenya, eastern Kenya, and Somalia: A broad area of anomalous lower-level convergence, coupled with upper-level divergence is expected to enhance rainfall in the region. Confidence: Moderate 10 – 16 April, 2018

12. Week-2 Precipitation Outlooks 17 – 23 April, 2018 • There is an increased chance for below-average rainfall over Sierra Leone, Liberia, southern Cote d’Ivoire, and southern Ghana: An area of anomalous lower-level divergence, coupled with upper-level convergence is expected to suppress rainfall in the region. Confidence: Moderate • There is an increased chance for above-average rainfall over eastern DRC, Rwanda, Burundi, Tanzania, Uganda, and western Kenya: A broad 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 Ethiopia and parts of Somalia and Kenya: A broad 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 seven days, rainfall was below-average over eastern of Liberia, many parts of Cote d’Ivoire, Ghana, Togo, Benin, Nigeria, much of Gabon, western and northern Angola, northern DRC, eastern CAR, local areas in southern Kenya and parts of Tanzania. In contrast, local areas in Guinea and Cote d’Ivoire, western Burkina Faso, southeastern Cameroon, eastern Gabon, much of Congo, western CAR, parts of South Sudan, many parts of Ethiopia, Uganda, Kenya, parts of Tanzania, Zambia, central and eastern Angola, parts of South Africa, and much of Madagascar had above-average rainfall. • During the past 30 days, eastern Guinea, parts of Cote d’Ivoire, western Burkina Faso, local areas in Ghana, parts of Togo and Benin, parts of southern Nigeria, Cameroon, CAR, South Sudan, Congo-Brazzaville and parts of DRC, southern and eastern Angola, northern Namibia, much of Tanzania, Uganda, Rwanda, Burundi and Kenya, South Sudan, parts of Ethiopia, local areas in southern Somalia, parts of Zambia, local areas in Malawi, parts of Botswana and Zimbabwe, portions of South Africa, local areas in Mozambique, and portions of Madagascar had above-average rainfall. In contrast, much of Gabon, parts of Angola and DRC, local areas in Zimbabwe, parts of Mozambique, and central and southern Madagascar had below-average rainfall. • During the past 90 days, above-average rainfall was observed over Sierra Leone, eastern Guinea, Cote d’Ivoire, parts of Ghana, Togo, Benin, southern Nigeria, Cameroon, CAR, South Sudan, portions of Congo-Brazzaville, parts of DRC and Angola, southern Ethiopia, Kenya, Tanzania, portions of Zambia, much of Zimbabwe, Botswana, parts of Mozambique, many parts of South Africa, and northern and eastern Madagascar. In contrast, rainfall was below-average over much of Gabon, local areas in Congo-Brazzaville, parts northern Angola, parts of DRC and Ethiopia, much of Namibia, local areas in Botswana South Africa, southern Malawi, local areas in Zambia and Mozambique, and western and southern Madagascar. • Week-1 outlooks call for an increased chance for above-average rainfall over Sierra Leone, Liberia, western and northern Angola, southern and eastern DRC, Rwanda, Burundi, western and southern Tanzania, southern Uganda, southwestern and northeastern Kenya, eastern and southern Ethiopia, portions of Somalia, Malawi, and northern Mozambique. In contrast, there is an increased chance for below-average rainfall over northern DRC, southern CAR and western South Sudan.