The African Monsoon Recent Evolution and Current Status Update prepared by Climate Prediction Center / NCEP 14 April 2008 For more information, visit:

Outline Highlights Recent Evolution and Current Conditions NCEP GEFS Forecasts Experimental Week-1 Outlook Summary

Highlights Last 7 Days Heavy rains persisted along coastal Tanzania and the western Ethiopian Highlands, while eastern Ethiopia and southern Somalia received beneficial rains Rainfall was near average across most areas in Kenya, except for the central part, where it was below average. Rainfall was also below average over parts of Uganda. Light rains resulted in below average rainfall along coastal portions of the Guinea coast. Light rains continued to sustain moisture deficits over portions of DRC.

Rainfall Patterns: Last 7 Days During the past 7 days, rainfall persisted over the western Ethiopian Highlands and increased over eastern Ethiopia and southern Somalia. Heavy rains also persisted along coastal Tanzania. Rainfall was below average over southwestern Kenya and Uganda, and along much of the Guinean coast.

Rainfall Patterns: Last 30 Days Over the last 30 days, rainfall was above average over most areas in Tanzania, southern Zambia, and portions of southern Africa. Rainfall was also above average over parts of central Africa. However, below average conditions prevailed over the central areas of Ethiopia and Kenya, much of Madagascar, northern Mozambique, northern Angola, southern DRC, and many countries in the Gulf of Guinea region.

Rainfall Patterns: Last 90 Days Over the past 90 days, rainfall was above average over parts of western southern Africa, northern Mozambique, and Tanzania. Rainfall was below average over parts of the Gulf of Guinea region, southern DRC and northern Angola, Zambia, Malawi, southern Mozambique, and Zimbabwe.

Rainfall Patterns: Last 180 Days Over the past 180 days, rainfall was above average across most areas in southern Africa. Rainfall was below average over portions of the central areas of Africa and the Greater Horn, including Kenya, Uganda, and Ethiopia. Rainfall was also below average over western coastal Guinea.

Recent Rainfall Evolution The recovery of the Belg rains continued in southern Ethiopia continued (top panel - right); Rainfall returned to southwestern Kenya following a short dry spell (bottom panel – right); Alternating frequent wet and dry episodes along portions of the Guinean coast over the past few weeks (bottom panel – left).

Atmospheric Circulation: Last 7 Days Over the past 7 days, the St. Helen and Mascarene High pressure systems (indicated with SH and MH - left panel) respectively over the Atlantic and the Indian Ocean, strengthened. Low level anomalous cyclonic circulation developed over northeastern Atlantic. Feature associated with a upper level cyclonic/anticyclonic couplet over northern Africa. Low level easterlies prevailed across West Africa and over the central Indian Ocean south of the equator. L SH MH

NCEP GEFS Model Forecasts Non-Bias Corrected Probability of precipitation exceedance – Week-1 Valid Apr, 2008 NCEP global ensemble forecast system (GEFS) suggests a high tilt in the odds (90% or above) for precipitation to exceed 25 mm along coastal Tanzania, sections of southwestern and northeastern Kenya, portions of Ethiopia, and local areas in the Gulf of Guinea region (left panel). The highest chance for precipitation to exceed 50 mm (right panel) is confined along coastal Tanzania.

Experimental Week-1 Precipitation Outlook Valid Apr, 2008

Summary Over the past seven days, heavy rains persisted along coastal Tanzania and the western Ethiopian Highlands. Eastern Ethiopia and southern Somalia received beneficial rains in a long time. However, rainfall was near average across most areas in Kenya, except for the central part, where it was below average. Rainfall was also below average over parts of Uganda, and along much of the Guinean coast. Over the last 30 days, heavy rains sustained moisture surpluses over most areas in Tanzania and southern Kenya. Rainfall was also slightly above average over western Ethiopia and southern Somalia. In contrast, light rains resulted in moisture deficits over central Ethiopia, parts of the Gulf of Guinea region, and further south over southern DRC, northern Angola, northern Mozambique, Malawi, and Madagascar. Moisture was slightly above average over CAR, northern Congo, and southwestern Cameroon. Over the last 90 days, rainfall was above average over parts of western southern Africa, northern Mozambique, and Tanzania. Rainfall was below average over Zambia, northern Angola, the southern areas of DRC and Congo, and central Ethiopia. Rainfall was slightly below average over western Kenya, northern Uganda, and along coastal Guinea. Season-to-date rainfall in southern Africa, starting from October 2008, has been overall above average, except for Madagascar. However, the light rains of the past few weeks in the northern areas of Zambia and Angola, and the southern areas of DRC, Congo, and western Gabon resulted in below average rainfall in this subregion. For the period 15– 21 April 2008, The NCEP global ensemble forecast system (GEFS) suggests 90% or above chance for precipitation to exceed 25 mm along coastal Tanzania and locally over southern Ethiopia. There is a high chance for precipitation to exceed 50 mm along coastal Tanzania.