The African Monsoon Recent Evolution and Current Status Update prepared by Climate Prediction Center / NCEP 23 March 2009 For more information, visit:

Outline Highlights Recent Evolution and Current Conditions NCEP GEFS Forecasts Summary

Highlights: Last 7 Days During the past week heavy rains soaked portions of Zambia and Madagascar resulting in moisture surpluses in those areas. The rainy season is off to a good start in the Gulf of Guinea region as moderate rains continued to fall. Light or no rain persisted in parts of eastern Africa, including Ethiopia and Kenya.

Rainfall Patterns: Last 180 Days Over the past 180 days, rainfall was near or above average across most areas in continental southern Africa. Rainfall enhancement was greatest in northern Namibia and southern Angola. However, northern Angola and southern DRC, as well as southern Kenya and Gabon received below average rainfall. Rainfall was also below average over northern Madagascar. Further to the north, rainfall was slightly above average along the Guinea coast over West Africa.

Rainfall Patterns: Last 90 Days During the past 90 days, rainfall was above average over most areas in continental southern Africa. The largest moisture surpluses occurred over northwestern Namibia. In contrast, rainfall was below average over most areas in northern Madagascar and along coastal Mozambique. Rainfall was also below average over eastern Tanzania, most areas in Kenya, and the western half of DRC southward into northern Angola. Rainfall was slightly above average in local areas along the Guinea coast.

Rainfall Patterns: Last 30 Days During the last 30 days, rainfall was above average from along the boundary between DRC and Tanzania southward into Zambia, southern Angola, western Namibia, and northern Botswana. Rainfall was below average over northern Angola and in local areas over Gabon and Congo. Rainfall was also below average over western Uganda, southwestern Kenya, and south central Ethiopia.

Rainfall Patterns: Last 7 Days During the past week, heavy downpours soaked parts of Zambia, northern Zimbabwe, central Mozambique, and Madagascar, resulting above average rains in those areas. In contrast, rainfall was below average over in the western part of continental southern Africa from Gabon southward to northwestern Namibia. Rainfall was also below average along coastal Tanzania. Seasonable rains fell along the Guinean coast.

Recent Rainfall Evolution Daily rainfall evolution during the last 90 days shows a good start to the rainy season in the Gulf of Guinea region in West Africa (bottom left), while rainfall is off to a slow start in parts of East Africa (bottom right). Light rains continued to sustain moisture deficits over parts of Ethiopia (top right).

Atmospheric Circulation: Last 7 Days Over the past 7 days, the 850 hPa wind anomaly (left panel) featured westerly wind anomalies over the Gulf of Guinea region and easterly anomalies over the equatorial western Indian Ocean. The 200 hPa wind anomaly (right panel) featured an anomalous ridge centered over Saudi Arabia coupled with an anomalous cyclonic circulation centered over the Sahara desert.

NCEP GEFS Model Forecasts Non-Bias Corrected Probability of precipitation exceedance Week-1: Valid March, 2009 Week-2: Valid April, 2009 For week-1, the global ensemble forecast system (GEFS) suggests over 90% chance for precipitation to exceed 50 mm in isolated areas including Gabon and the Mozambique Channel. For week-2, the model exhibits a chance for precipitation to exceed 50 mm over northern Angola, along the north coast of Mozambique, and over the northern tip of Madagascar.

Experimental Week-1 & Week-2 Precipitation Outlooks Week-1 Outlook Valid 24 –30 March, An increased chance for below average rainfall: Dry low level north winds turning into easterlies are expected to suppress precipitation in this region. Confidence: Moderate Climatology is expected for week-2

Summary During the past week, heavy downpours soaked parts of Zambia, northern Zimbabwe, central Mozambique, and Madagascar, resulting above average rains in those areas. In contrast, rainfall was below average over in the western part of continental southern Africa from Gabon southward to northwestern Namibia. Rainfall was also below average along coastal Tanzania. The rainfall season is off the a slow start in parts of eastern Africa, as light or no rain fell in many parts of the region. In contrast, rainfall was slightly above average in the Gulf of Guinea region. During the last 30 days, rainfall was above average from along the boundary between DRC and Tanzania southward into Zambia, southern Angola, western Namibia, and northern Botswana. Rainfall was below average over northern Angola and in local areas over Gabon and Congo. Rainfall was also below average over western Uganda, southwestern Kenya, and south central Ethiopia. The Outlook for week1 calls for below average rainfall over portions of central Africa, including southern Cameroon, Gabon, Congo, DRC, and northern Angola.