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 10 January 2011 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 • Heavy rains continued to drench parts of northern Namibia and southern Angola with satellite rainfall estimates exceeding 100 mm in local areas. The rains may sustain threats for local flooding. Heavy rains brought relief to northern Mozambique • Dry conditions sustained moisture deficits in Tanzania and Madagascar. • Week-1 forecasts call for enhanced rainfall activity along coastal Angola and Namibia, and over the eastern part of southern Africa. Suppressed rainfall is expected over portions of central Africa. • Week-2 outlooks valid January 18-24 call for suppressed rainfall along coastal Angola and Namibia, and over the northeastern sector of southern Africa. Above average rainfall is expected over parts of central Africa extending into the Maize Triangle of South Africa.

4. Rainfall Patterns: Last 7 Days During the past seven days, rainfall was variable across southern Africa. The area along the border between northern Namibia and southern Angola, portions of the Maize Triangle of South Africa continued to receive sizable rainfall amounts. Moderate to heavy rains also fell along coastal Tanzania and over northern Mozambique. In contrast, light rains sustained moisture deficits over much of Madagascar, the southern areas of Mozambique and Zimbabwe, parts of Malawi, and most areas in Tanzania. Below average rainfall was observed for two consecutive weeks in Zambia. Rainfall was below average over eastern DRC and enhanced over Congo, Gabon, and southern Cameroon.

5. Rainfall Patterns: Last 30 Days During the past 30 days, rainfall was above average over much of South Africa, western Botswana, and Angola. Rainfall was below average over Madagascar, portions of central and northern Mozambique, much Tanzania, Kenya, southern Somalia, and southwestern Ethiopia. In central Africa, rainfall was below average over northern DRC. However, above average rainfall was observed across much of central and southern DRC, and the southern areas of Congo and Gabon. Rainfall was above average locally over parts of the Gulf of Guinea region.

6. Rainfall Patterns: Last 90 Days During the past 90 days, rainfall was above average over many areas in southern Africa, except for the north and central east coast of Madagascar. In contrast, rainfall was below average over parts of Tanzania, much of Kenya, Somalia, and Ethiopia. Rainfall was also below average over DRC. Rainfall was above average over the western part of central Africa, including portions of Congo, southern Gabon, CAR, Cameroon, and areas in the Gulf of Guinea region.

7. Rainfall Patterns: Last 180 Days During the past 180 days, rainfall was above average over much of West Africa, except for central Nigeria. Rainfall was also above average over parts of central Africa including southern Chad, southern Cameroon, central Congo, and southern Gabon. Rainfall was below average over eastern DRC. In east Africa, rainfall was above average over northern Ethiopia, and below over eastern Kenya and southern Somalia. In southern Africa, rainfall was above average over southern Madagascar, central Mozambique, southern Zambia, and in local areas over western Botswana and central Angola. Rainfall was below average along east coast Madagascar.

8. Recent Rainfall Evolution Daily evolution of precipitation at selected stations indicates that steady rains sustained moisture surpluses in parts of the Maize Triangle of South Africa (lower panel – left). Despite a small decline, rainfall continued to be above average over parts of central Mozambique (lower panel – right). Rainfall was slightly below average over portions of central Tanzania (upper panel – right ).

9. Atmospheric Circulation:Last 7 Days The 850 hPa wind anomalies (right panel) featured easterly wind anomalies over southern Madagascar feeding moisture into continental southern Africa. There is an anomalous cyclonic circulation centered off the coast of Namibia. Southeasterly wind anomalies were evident along the coastal Tanzania. These features combined with the circulation pattern in the 200 hPa wind anomaly map (left panel) may have contributed to the observed precipitation anomalies of the past week.

10. NCEP GEFS Model ForecastsNon-Bias Corrected Probability of precipitation exceedance Week-1: Valid 11 - 17 January 2011 Week-2: Valid 18 - 24 January, 2011 For week-1, there is a high chance for precipitation to exceed 50 mm over central Mozambique, Zimbabwe, and southern Zambia. For week-2, the chance for precipitation to exceed 50 mm is highest in western Zambia.

11. Experimental Week-1 Precipitation Outlooks • There is an increased chance for below average rainfall over parts of central Africa: The eastward shift of the meridional arm of the ITCZ and the projected phase of the MJO signal are expected to suppress rainfall in the region.Confidence: Moderate • There is an increased chance for above average rainfall along coastal Angola and Namibia: Anomalous westerlies from the warm southeast Atlantic Ocean and their associated convergence are expected to enhance rainfall in the region. Confidence: Moderate • There is an increased chance for above average rainfall over eastern southern Africa: The eastward shift of the meridional arm of the ICTZ converging with anomalous moist easterlies from the western Indian Ocean are expected to increase rainfall in the region. Confidence: Moderate • There is an increased chance for tropical cyclone development across northern Madagascar and the Mozambique Channel: Above normal SST and low vertical wind shear are expected to enhance rainfall in this region. Confidence: Moderate. Week-1 Outlook 11 - 17 January, 2011

12. Experimental Week-2 Precipitation Outlooks Week-2 Outlook 18 – 24 January 2011 • There is an increased chance for below average • rainfall along coastal Angola and Namibia: • The projected phase of the MJO is expected to • suppress rainfall in this region. • Confidence: Moderate. • 2. There is an increased chance for above average • rainfall over parts of central Africa and southern • Africa: The phase of the MJO combined with • La Nina is expected to enhance rainfall in this • region. Confidence: Moderate. • There is an increased chance for below average • rainfall over northeastern southern Africa: • The phase of the MJO is expected to suppress • rainfall in this region. Confidence: Moderate.

13. Summary During the past seven days, rainfall was variable across southern Africa. The area along the border between northern Namibia and southern Angola, portions of the Maize Triangle of South Africa continued to receive sizable rainfall amounts. Moderate to heavy rains also fell along coastal Tanzania and over northern Mozambique. In contrast, light rains sustained moisture deficits over much of Madagascar, the southern areas of Mozambique and Zimbabwe, parts of Malawi, and most areas in Tanzania. Below average rainfall was observed for two consecutive weeks in Zambia. Rainfall was below average over eastern DRC and enhanced over Congo, Gabon, and southern Cameroon. During the past 30 days, rainfall was above average over much of South Africa, western Botswana, and Angola. Rainfall was below average over Madagascar, portions of central and northern Mozambique, much Tanzania, Kenya, southern Somalia, and southwestern Ethiopia. In central Africa, rainfall was below average over northern DRC. However, above average rainfall was observed across much of central and southern DRC, and the southern areas of Congo and Gabon. Rainfall was above average locally over parts of the Gulf of Guinea region. During the past 90 days, rainfall was above average over many areas in southern Africa, except for the north and central east coast of Madagascar. In contrast, rainfall was below average over parts of Tanzania, much of Kenya, Somalia, and Ethiopia. Rainfall was also below average over DRC. Rainfall was above average over the western part of central Africa, including portions of Congo, southern Gabon, CAR, Cameroon, and areas in the Gulf of Guinea region. For week-1, there is an increased chance for above average rainfall along coastal Angola and Namibia, and over the eastern part of southern Africa from Tanzania to the Maize Triangle of South Africa. Suppressed rainfall is expected over portions of central Africa. There is an increased chance for tropical cyclone development over the Mozambique Channel. For week-2, there is an increased chance for below average rainfall along coastal Angola and Namibia, and over the northeastern sector of southern Africa. Above average rainfall is expected over parts of central Africa and the Maize Triangle of South Africa.