The African Monsoon Recent Evolution and Current Status Update prepared by Climate Prediction Center / NCEP 20 April 2009 For more information, visit:

Outline Highlights Recent Evolution and Current Conditions NCEP GEFS Forecasts Summary

Highlights: Last 7 Days Moderate to heavy rains brought relief to areas in southwestern Ethiopia, parts of Uganda, and southwestern Kenya. Moderate to heavy rains sustained moisture surpluses over parts of the Gulf of Guinea region.

Rainfall Patterns: Last 180 Days Over the past 180 days, rainfall was above average across most areas in continental southern Africa and along the east coast of Madagascar. Rainfall was below average along the northwest coast of Madagascar, northern Angola, southern and central DRC. Rainfall was also below average over southern Kenya. In central Africa, rainfall was below average over southern Gabon, while northern Congo, and coastal Cameroon received above average rainfall. Parts of the Gulf of Guinea region in West Africa also received above average rainfall.

Rainfall Patterns: Last 90 Days During the past 90 days, rainfall was above average over northern Namibia and southern Angola. In contrast, rainfall was below average over eastern Zimbabwe, central and southern Mozambique, and western Madagascar. Further to the north, rainfall was above average over much of Tanzania, southern Uganda, and parts of eastern DRC. Rainfall was above average locally over southeastern CAR. Northern Congo, and coastal Cameroon.

Rainfall Patterns: Last 30 Days During the last 30 days, Tropical Cyclones Izilda and Jade dumped heavy downpours in parts of Madagascar resulting in above average rainfall in the eastern and southern areas of this country. Rainfall was near average across much of continental southern Africa from central Mozambique and Zimbabwe southward the South Africa. However, light rains resulted in moisture deficits over much of Angola and western Zambia. Rainfall was also below average over southern Kenya, in local areas over southeastern and central DRC, and over central Gabon. In the Gulf of Guinea region of West Africa, rainfall was above average over parts of Cote d’Ivoire, and much of Ghana and Togo.

Rainfall Patterns: Last 7 Days During the past week, seasonably dry weather settled in southern Africa as the ITCZ continued its northward migration. Light to moderate rains resulted in near average conditions over central Africa with a slight dry bias over southern DRC and a wet bias in local areas in the north and southern Congo. Moderate to heavy rains improved conditions in local areas over southwestern Kenya and parts of southwestern Ethiopia. In the Gulf of Guinea region, moderate the heavy rains sustained moisture surpluses over Cote d’Ivoire, Ghana, Togo, Benin, and parts of Nigeria.

Recent Rainfall Evolution Daily rainfall evolution during the last 90 days shows that rainfall continued to increase in the Gulf of Guinea region in West Africa (bottom left). (bottom right). Light rains sustained moisture deficits over southern Kenya (bottom right). Beneficial rains fell over southwestern Ethiopia over the past week resulting in reduced moisture deficits (top right).

Atmospheric Circulation: Last 7 Days Over the past 7 days, the 850 hPa wind anomaly (left panel) featured an anomalous low level cyclonic circulation centered over the south Indian Ocean south of Madagascar. There was an anomalous southerly flow along the east coast of Africa that extended from the Mozambique Channel into the central Indian Ocean. Along the equator, there were westerly anomalies converging over the Gulf of Guinea region with an anomalous easterly flow from the Congo basin.

NCEP GEFS Model Forecasts Non-Bias Corrected Probability of precipitation exceedance Week-1: Valid April, 2009 Week-2: Valid 28 April - 4 May, 2009 For week-1 and week-2, the global ensemble forecast system (GEFS) suggests over 80% chance for precipitation to exceed 50 mm over parts of Central Africa, including Gabon and southern Cameroon.

Experimental Week-1 & Week-2 Precipitation Outlooks Week-1 Outlook Valid April, An increased chance for below average rainfall over parts of central and eastern Africa: As the active phase of the MJO is projected to enter the western Pacific region, precipitation is expected to be suppressed in this region. Confidence: Moderate Week-2 Outlook Valid 28 April – 4 May 2009 Climatology is expected across Africa

Summary During the past week, seasonably dry weather settled in southern Africa as the ITCZ continued its northward migration. Light to moderate rains resulted in near average conditions over central Africa with a slight dry bias over southern DRC and a wet bias in local areas in the north and southern Congo. Moderate to heavy rains improved conditions in local areas over southwestern Kenya and parts of southwestern Ethiopia. In the Gulf of Guinea region, moderate the heavy rains sustained moisture surpluses over Cote d’Ivoire, Ghana, Togo, Benin, and parts of Nigeria. During the last 30 days, Tropical Cyclones Izilda and Jade dumped heavy downpours in parts of Madagascar resulting in above average rainfall in the eastern and southern areas of this country. Rainfall was near average across much of continental southern Africa from central Mozambique and Zimbabwe southward the South Africa. However, light rains resulted in moisture deficits over much of Angola and western Zambia. Rainfall was also below average over southern Kenya, in local areas over southeastern and central DRC, and over central Gabon. In the Gulf of Guinea region of West Africa, rainfall was above average over parts of Cote d’Ivoire, and much of Ghana and Togo. As the MJO is projected to propagate east and the active phase likely to be located the western Pacific during week1, precipitation is expected to be suppressed over parts of central and eastern Africa during the period April 2009.