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Posted 5 July 2011

 


Greater Horn of Africa Climate Outlook Forum Considers July-September Rainfall

Severe drought has persisted over most parts of the eastern sector of the equatorial Greater Horn of Africa since the last quarter of 2010 with far reaching socio-economic implications.

The Greater Horn of Africa Climate Outlook Forum issued a consensus statement following a 17 June meeting convened by the Intergovernmental Authority on Development Climate Prediction and Applications Centre (ICPAC), WMO, United Kingdom Met Office and other partners.

It said there is an “increased likelihood” of above normal rainfall over Central Sudan and western Ethiopia in July-September. Above-normal rainfall is defined as within the wettest third of long term recorded rainfall amounts.

It said there is an increased likelihood of above to near normal rainfall over Eritrea, Djibouti, Uganda, Rwanda, northern Burundi, northwestern Tanzania, Western Kenya, extreme northwestern Somalia, southwestern, central and northeastern Ethiopia, as well as southern and parts of northeastern Sudan. Near normal rainfall is defined as the third of the recorded rainfall amounts centred around the climatological median.

Consensus Climate Outlook July-Sept 2011: ICPAC

jpegThe rest of the Greater Horn of Africa region – including drought.hit parts of the eastern sector – is likely to remain seasonally dry, it said.

July-September constitutes a major rainfall season over much of the Greater Horn of Africa’s northern sector (Sudan, Djibouti, Ethiopia, Eritrea and northern Somalia) and the western parts of the equatorial sector. 

The outlook is relevant only for seasonal time scales and relatively large areas. Local and month to-month variations may occur. Forecast updates will be provided by ICPAC and the respective National Meteorological and Hydrological Services

The rest of the Greater Horn of Africa region – including drought.hit parts of the eastern sector – is likely to remain seasonally dry, it said.

July-September constitutes a major rainfall season over much of the Greater Horn of Africa’s northern sector (Sudan, Djibouti, Ethiopia, Eritrea and northern Somalia) and the western parts of the equatorial sector. 

The outlook is relevant only for seasonal time scales and relatively large areas. Local and month to-month variations may occur. Forecast updates will be provided by ICPAC and the respective National Meteorological and Hydrological Services.

July-Sept Long Term Mean Rainfall: ICPAC

Much of the equatorial sector of the Greater Horn of Africa (Kenya, Uganda, Burundi, Rwanda, southern Somalia and northern Tanzania) has two major seasonal rainfall peaks during March-May and October-December. The western and coastal parts receive significant rainfall during July-August.

The persistence of the severe drought over parts of the Eastern sector of equatorial Greater Horn of Africa (including parts of Ethiopia, Kenya and Somalia) since the last quarter of 2010 has been associated with La Niña conditions (unusually cool ocean surface temperatures in the central and eastern tropic Pacific). 

The La Niña episode, which started in July 2010, has now ended and been replaced by near-neutral conditions, with the ocean temperatures, tropical rainfall patterns, and atmospheric winds over the equatorial Pacific Ocean being near the long-term average. It is too early to assess what impact this will have on the October-December rainfall in drought-hit areas.

La Niña is characterized by unusually cool ocean surface temperatures in the central and eastern tropical Pacific. It is the opposite of El Niño, which is characterized by unusually warm ocean surface temperatures in the same area. Both events drive the large-scale ocean-atmosphere circulation patterns in the tropics and have important consequences for weather and climate around the globe. Once established, they typically last for 9 months or more.

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