The African Monsoon Recent Evolution and

Current Status

Include Week-1 and Week-2 Outlooks

Update prepared byClimate Prediction Center / NCEP

07 November 2011For more information, visit:http://www.cpc.ncep.noaa.gov/products/Global_Monsoons/African_Monsoons/precip_monitoring.shtml

Outline

• Highlights• Recent Evolution and Current Conditions• NCEP GEFS Forecasts• Summary

Highlights:Last 7 Days

• Rainfall surpluses exceeded 100mm over parts of central Somalia and southeastern Ethiopia.

• Week-1 outlooks call for an increased chance for above average rainfall over southern Gabon, southern Congo, many parts of DRC, western Angola, southern South Sudan Republic, western Uganda, Rwanda, Burundi, northwestern Tanzania, eastern Kenya, southern and central Somalia, portions of Southeast Ethiopia and coastal Tanzania.

Rainfall Patterns: Last 7 Days

During the past seven days, below average rainfall was observed across the Gulf of Guinea coast, many parts of Cameroon, northern Gabon, CAR, portions of Congo, much of DRC, parts of Angola, eastern Kenya, southern Somalia, portions of South Sudan Republic and western Madagascar. In contrast, Parts of Guinea, local areas of Nigeria, southern Gabon, local areas of Congo, central Angola, southern DRC, portions of Zambia and parts of Madagascar received above average rainfall. Heavy rains that persisted across the Horn of Africa resulted in moisture surpluses over eastern Uganda, western Kenya, central Somalia and many parts of Ethiopia.

Rainfall Patterns: Last 30 Days

During the past 30 days, moisture surpluses exceeded 150mm over Northeast Kenya, southern Somalia, portions of Southeast Ethiopia and coastal Gabon. Many parts of Cote D’Ivoire, western Burkina Faso, portions of southern Ghana, Togo, Benin, western and eastern Nigeria, portions of Cameroon, Congo, Gabon, eastern CAR, South Sudan Republic, much of DRC, northern Angola, northern Zambia, northeastern South Africa and portions of Madagascar also received above average rainfall. In contrast, below average rainfall was observed over southern Senegal, Gambia, northern Guinea, southern Mali, portions of southern Chad, Ethiopia, many parts of Angola, northeastern Namibia, western Botswana, central South Africa and Lesotho.

Rainfall Patterns: Last 90 Days

During the past 90 days, below average rainfall was observed over coastal Guinea, Sierra Leone, parts of Liberia, central Nigeria, eastern Sudan, Ethiopia and portions of central Angola. Eastern Senegal, northern Guinea, central Mali, southern Ghana, eastern Burkina Faso, western Chad, portions of CAR and Cameroon, Gabon, northern Congo Brazzaville, much of DRC, Uganda, portions of Kenya, southern and central Somalia, and southeastern Ethiopia had above average rainfall.

Rainfall Patterns: Last 180 Days

During the past 180 days, rainfall was below average over southern Senegal, coastal Guinea Conakry, Sierra Leone, portions of Cote D’Ivoire, western Niger, Much of Nigeria, portions of Cameroon, northern Gabon, eastern Sudan, Eritrea and Ethiopia. Moisture surpluses were observed over northern Guinea Conakry, central Mali, Ghana, local areas of Chad, CAR, southern Gabon, northern Congo Brazzaville, central and eastern DRC, Uganda, western and eastern Kenya, southern and central Somalia, and southeastern Ethiopia.

Recent Rainfall Evolution

Daily evolution of rainfall over the last 90 days at selected stations reflects the suppressed rainfall over central Angola (bottom panel-left) and portions of South Africa (bottom panel – right), and the persistent above average rainfall in portions of the GHA region (top panel – right).

Atmospheric Circulation:Last 7 Days

The 850hPa wind anomaly (left panel) featured convergence between northwesterly and southwesterly anomalies across the GHA region, which may have contributed to the observed heavy rainfall in this region. There were also westerly anomalies over western parts of Equatorial Africa and northwesterly anomalies across central African region. The 200hpa wind anomaly (right panel) featured strong easterly anomalies over western Indian Ocean and the neighboring areas of East Africa.

NCEP GEFS Model ForecastsNon-Bias Corrected Probability of

precipitation exceedance Week-1: Valid 08 – 14 November 2011Week-2: Valid 15 – 21 November 2011

For week-1 (left panel) and week-2 (right panel), there is an increased chance for rainfall to exceed 50 mm over Equatorial Guinea, Gabon, Congo, much of DRC, northern Angola and eastern Kenya.

Experimental Week-1 Precipitation Outlooks

Week-1 Outlook08 – 14 November 2011

1. There is an increased chance for above average precipitation over southern Gabon, southern Congo, western DRC and western Angola: The combination of moist westerly anomalies from the Atlantic Ocean and the projected phase of the MJO is expected to enhance rainfall in the region. Confidence: Moderate

2. There is an increased chance for above average rainfall over eastern DRC, southern South Sudan Republic, western Uganda, Rwanda, Burundi and northwestern Tanzania: Stronger than normal convergence in the Congo Air Boundary (CAB) area is expected to enhance rainfall in the region. Confidence: Moderate

3. There is an increased chance for above average precipitation over eastern Kenya, southern and central Somalia, portions of Southeast Ethiopia and coastal Tanzania: Moist easterly anomalies from the Indian Ocean, with their convergence in the Horn of Africa are expected to enhance rainfall in the region. Confidence: Moderate

Experimental Week-2 Precipitation Outlooks

Week-2 Outlook15 – 21 November 2011

1. There is an increased chance for above average rainfall over Equatorial Guinea, Gabon, Congo Brazzaville, northern Angola and much of DRC: The projected phase of the MJO is expected to enhance rainfall in the regions. Confidence: Moderate

Summary

• During the past seven days, below average rainfall was observed across the Gulf of Guinea coast, many parts of Cameroon, northern Gabon, CAR, portions of Congo, much of DRC, parts of Angola, eastern Kenya, southern Somalia, portions of South Sudan Republic and western Madagascar. In contrast, Parts of Guinea, local areas of Nigeria, southern Gabon, local areas of Congo, central Angola, southern DRC, portions of Zambia and parts of Madagascar received above average rainfall. Heavy rains that persisted across the Horn of Africa resulted in moisture surpluses over eastern Uganda, western Kenya, central Somalia and many parts of Ethiopia.

• During the past 30 days, moisture surpluses exceeded 150mm over Northeast Kenya, southern Somalia, portions of Southeast Ethiopia and coastal Gabon. Many parts of Cote D’Ivoire, western Burkina Faso, portions of southern Ghana, Togo, Benin, western and eastern Nigeria, portions of Cameroon, Congo, Gabon, eastern CAR, South Sudan Republic, much of DRC, northern Angola, northern Zambia, northeastern South Africa and portions of Madagascar also received above average rainfall. In contrast, below average rainfall was observed over southern Senegal, Gambia, northern Guinea, southern Mali, portions of southern Chad, Ethiopia, many parts of Angola, northeastern Namibia, western Botswana, central South Africa and Lesotho.

• During the past 90 days, below average rainfall was observed over coastal Guinea, Sierra Leone, parts of Liberia, central Nigeria, eastern Sudan, Ethiopia and portions of central Angola. Eastern Senegal, northern Guinea, central Mali, southern Ghana, eastern Burkina Faso, western Chad, portions of CAR and Cameroon, Gabon, northern Congo Brazzaville, much of DRC, Uganda, portions of Kenya, southern and central Somalia, and southeastern Ethiopia had above average rainfall.

• Week-1 outlooks call for an increased chance for above average rainfall over southern Gabon, southern Congo, many parts of DRC, western Angola, southern South Sudan Republic, western Uganda, Rwanda, Burundi, northwestern Tanzania, eastern Kenya, southern and central Somalia, portions of Southeast Ethiopia and coastal Tanzania.