Statement from the fourteenth Climate Outlook Forum for the Greater Horn of Africa

23 -26 August 2004, Nairobi, Kenya

Summary

There is increased likelihood of near-normal rainfall over much of the Greater Horn of Africa during September to December 2004 season. High likelihood of near normal to above normal rainfall is indicated over northeastern Sudan, northern Eritrea, southern Djibouti, central and western Ethiopia and southern Sudan, much of Uganda a part from south-western areas, much of western Rwanda, much of Burundi, western and northeastern Tanzania, coastal, southern and western Kenya and eastern Somalia. Central Sudan, northern and southeastern Ethiopia, western Somalia, much of northern Kenya, northeastern and southwestern Uganda, northwestern and eastern Rwanda, eastern Burundi as well as southern, central and northwestern Tanzania have increased likelihood of near-normal to below normal rainfall. It may be recalled that some parts of the region have experienced drought conditions for the past several months. The projected near normal rainfall conditions in the coming season may not be sufficient to wipe out the impacts of the accumulated rainfall deficits that have persisted over parts of these areas. It should also be noted that heavy and short duration episodic events and flush floods are common in many areas of the sub-region, especially over the arid and semi arid zones even during the seasons with below normal rainfall conditions.

The outlook is relevant only for seasonal time scales and relatively large areas. Local and month-to-month variations may occur. Warmer than normal Sea Surface Temperatures have been observed over the central and eastern equatorial Indian Ocean as well as southern Atlantic Ocean. However, colder than normal sea surface temperatures have been observed over north-western Indian Ocean but they are projected to lean towards near-normal conditions during the forecast period. Forecast model outputs also indicate that there is a high likelihood that warmer than normal Sea Surface Temperatures (SSTs), that is often referred to as El-Niño, could develop over the equatorial central Pacific Ocean. Such conditions may not affect the climate of the sub region at the beginning of the season, but could have far reaching impacts towards the end of the forecast period. For example, some of the past El-Niño events have been associated with heavy rainfall occurring between November – February period. Forecast updates will be provided by the National Meteorological Services (NMSs) and the IGAD Climate Prediction and Applications Centre (ICPAC - formerly DMCN). The users are therefore strongly advised to keep in contact with their National Meteorological Services for interpretation of this outlook, finer details, updates and additional guidance.

The Climate Outlook Forum

From 23 to 26 August 2004, the fourteenth Climate Outlook Forum was convened in Nairobi, Kenya by the ICPAC in collaboration with the National Meteorological and Hydrological Services (NMHSs) and partners to formulate consensus guidance for the September to December 2004 rainfall season in the Greater Horn of Africa (GHA). The forum reviewed the state of the global climate system and its implications on the seasonal climate of the sub-region. Among the principal factors taken into account were the observed and predicted SSTs in the tropical Pacific Ocean and over much of the tropical Atlantic and Indian Oceans. Users from Agriculture and Food Security, disaster management, health, livestock, water resources and media among other sectors were active participants in the forum. The users formulated the potential implications of the outlook for September to December 2004 season and developed mitigation strategies for the respective countries and sectors.
Methodology

The forum examined the current and expected SST anomalies over the Pacific Ocean as well as the Indian and Atlantic Oceans together with other factors that affect the climate of the sub region. These factors were assessed using coupled ocean-atmosphere and Regional Dynamical Climate models and empirical statistical models as well as expert interpretation. The current capability of seasonal to inter-annual forecasting allows prediction of spatial and temporal averages and may not fully account for the physical and dynamical factors that influence regional and national climate variability.

The experts established probability distributions to indicate the likelihood of above-, near-, or below-normal rainfall for each zone (see Map). Above-normal rainfall is defined as within the wettest third of recorded rainfall amounts in each zone; near-normal is defined as the third of the recorded rainfall amounts centred around the climatological median; below-normal rainfall as within the driest third of the rainfall amounts. Climatology refers to a situation where any of the three categories have equal chances of occurring.

Outlook

September to December constitutes an important rainfall season over much of the Greater Horn of Africa sub-region. The rainfall outlook for each zone within this sub-region is given below. Zone I: Increased likelihood of near to above-normal rainfall over northeastern Sudan and northern Eritrea.

Zone II: Climatology is suggested over northern Sudan, much of Eritrea, and Djibouti as well as extreme northern Ethiopia.

Zone III: Increased likelihood of near to below-normal rainfall over central Sudan and parts of northern Ethiopia.

Zone IV: Increased likelihood of near to above-normal rainfall over southern Djibouti, central, western and extreme eastern Ethiopia, southern Sudan, much of Uganda, northeastern Tanzania, coastal, southern, western and extreme northern parts of Kenya as well as eastern Somalia.

Zone V: Increased likelihood of near to below-normal rainfall over northeastern Uganda, much of northern Kenya, western Somalia and much of eastern Ethiopia.

Zone VI: Increased likelihood of near to above-normal rainfall over much of Rwanda and Burundi as well as western Tanzania.

Zone VII: Increased likelihood of near to below-normal rainfall over southwestern Uganda, northwestern and eastern Rwanda, eastern Burundi and much of Tanzania.

Note:

The numbers for each zone indicate the probabilities (chances of occurrence) of rainfall in each of the three categories, above-, near-, and below normal. The top number indicates the probability of rainfall occurring in the above-normal category; the middle number is for the near normal and the bottom number for the below-normal category. For example, in case of northeastern Sudan and northern Eritrea (zone I), there is 35% probability of rainfall occurring in the above normal category; 40% probability of rainfall occurring in the near-normal category; and 25% probability of rainfall occurring in the below normal category. It is emphasized that boundaries between zones should be considered as transition areas.

Contributors

The fourteenth climate outlook forum for the Greater Horn of Africa was organised jointly by the IGAD Climate Prediction and Applications Centre (ICPAC), World Meteorological Organisation (WMO), the National Oceanic and Atmospheric Administration / Office of Global Programs (NOAA / OGP) and the International Research Institute for climate prediction (IRI) within the framework of the United States Agency for International Development (USAID) funded project, “Sustainable generation and applications of climate information, products and services for disaster preparedness and sustainable development in the Greater Horn of Africa”.

Contributors to this consensus climate outlook included representatives of the Meteorological Services from ten GHA countries (Insititut Geographique du Burundi; Meteorologie Nationale de Djibouti; Eritrea Meteorological Services; National Meteorological Services Agency of Ethiopia; Kenya Meteorological Department; Rwanda Meteorological Service; Meteorology Department Somalia Republic; Sudan Meteorological Authority; Tanzania Meteorological Agency and Uganda Department of Meteorology) and climate scientists and other experts from national, regional and international institutions and organisations such as ICPAC; Drought Monitoring Centre, Harare; IRI; WMO; University of Nairobi and Maseno University. Additional inputs were provided by the National Centers for Environmental Prediction/Climate Prediction Center (NCEP/CPC), ECMWF and UK Met. Office.

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