CLIMATE WATCH FOR SEPTEMBER 2004

Executive summary

IGAD Climate Prediction and Applications Centre (ICPAC), formerly known as Drought Monitoring Centre - Nairobi (DMCN) provides regular regional climate advisories including ten day, monthly and seasonal climate bulletins as well as timely early warning information regarding climate hazards such as drought and floods and the associated impacts. Consensus seasonal climate outlooks are normally provided within the framework of the Regional Climate Outlook forums in collaboration with several international centres such as the International Research Institute for Climate Prediction (IRI), before the onset of the major rainfall seasons for timely early warning of any impending climate hazards such as drought and floods and the potential impacts. The fourteenth climate outlook forum (COF14) that was held in Nairobi between 23 and 27 August 2004 provided climate projections for September – December 2004 season.

ICPAC also occasionally publishes "the climate watch" bulletin in order to provide update information regarding any potential development of some unique climate hazards that could have significant impacts on the climate of the region. Parts of the sub-region have been under persistence drought for several months. COF14 climate outlook indicates that some of the areas that have been experiencing drought are likely to receive below normal rainfall during September – December period. Further some of these areas are located within the tropics where the next major rainfall season after October-December 2004 will be in March – May 2005.

Forecast model outputs from advanced climate centres 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 central equatorial Pacific Ocean. Some of the past El-Niño events have been associated with heavy rainfall occurring between November – February period. The current issue of the climate watch bulletin is to provide a review of the performance of the last two rainfall seasons as well as an update of the current and projected state of the climate system and their potential impacts in the Greater Horn of Africa (GHA) for the period October to December 2004.

March to May is the major rainfall season for many parts of the equatorial sector of the sub region. During March to May 2004, near normal to below normal rainfall was recorded over most parts of these areas with only localised areas receiving normal to above normal rainfall. In general, the performance of the March to May 2004 rainfall season, in many parts of the region, was not good, especially for food production. At many locations the onset of the rains was late, and the rains also ceased quite early. As a result, drought conditions have continued to bite many parts of the sub region.

June to September is the major rainfall season for the northern parts of the sub region and western parts of the equatorial sector. Normal to wet conditions were experienced over parts of the northern and western parts of the equatorial sectors. However the cumulated rainfall from March to September 2004 indicates that many parts of the sub region have been under significant moisture stress (drought) for several months. In fact, famine has been declared a national disaster in some countries of the sub?region, including Kenya.

Consensus climate outlook developed by ICPAC and partners at the (COF14) that was held in Nairobi between 23 - 27 August 2004 indicates that during the period September to December 2004 there is high likelihood of near normal to above normal rainfall over northeastern Sudan, northern Eritrea, southern Djibouti, central and western Ethiopia and southern Sudan, much of Uganda, much of western Rwanda, much of Burundi, western and northeastern Tanzania, coastal, southern and western Kenya and eastern Somalia. Increased likelihood of near-normal to below normal rainfall is indicated over 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 (see cover page).

Continued dry conditions of these areas will have severe implication on livestock, food security, water resources, health, and many other economic, environmental and societal factors. The moisture stress would lead to lack of water, famine, diseases, mass migration of animals and people among many other socio-economic miseries and exacerbate the already deteriorating situation with regard to food security. Food security outlook that was developed at COF14 by ICPAC, FEWS-NET, IRI, WFP, WMO and other partners confirmed the expected pathetic nature of food insecurity in the Greater Horn of Africa by the end of December 2004.

Some of the extreme climate events such as floods and droughts that have been observed in Greater Horn of Africa (GHA) have been linked to the occurrence of El Niño / La Niña events (the warming / cooling of Sea Surface Temperatures of the equatorial Pacific Ocean). Others have been related to unique evolution of Sea Surface Temperatures (SSTs) over the Indian and Atlantic Oceans. Forecast model outputs from advanced climate centres indicate that El Niño conditions are likely to develop towards the end of the year. Such condition 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 ICPAC. The users are therefore strongly advised to keep in contact with their National Meteorological and Hydrological Services for detailed national information, products and updates.

2. Seasonal Rainfall Assessment

Many socio-economic activities in the GHA region depend heavily on rainfall. As such, it is the most important climate element in the region. It is equally important due to its high degree of variability both in space and time and very strong seasonality. Based on the rainfall regimes, the sub-region can be divided into three sectors namely the northern, equatorial and Southern sectors.

Over much of the equatorial sector rainfall is concentrated within two peak seasons of March-May and October-December. However, the western and coastal areas also receive significant rainfall during the months of July-August. The northern sector has peak rainfall concentrated largely during the northern summer months of June to September with few areas receiving the secondary peak during March to May season. The southern parts of the sub region have peak rainfall concentrated mainly within the southern summer months of December to February.

2.1 March to May 2004

The March to May is the major rainy season in the equatorial sector. The rainfall totals compared to long term average for the season shows that many locations in the equatorial sector received rainfall amounts that were below the long term average for the season, see figure 1.

Figure 1: March to May 2004 rainfall compared to the long-term Mean (LTM) for the season over the
equatorial sector.

The spatial patterns of the Drought Severity Index for the month of May 2004 are shown in figure 2. The patterns indicate that very wet conditions were observed over parts of the equatorial and northern sectors of the sub-region. However dry conditions were observed over vast areas of the subregion with isolated areas experiencing driest conditions on record for the month since 1961 (see figure 2).

2.2 June to August 2004

The June to August season is a significant season in the northern sector. The June to August rainfall totals compared to long term average for the season shows that most of the stations in the northern sector received totals that were below the long term average for the season (see figure 3a).

Figure 3a: June to August 2004 rainfall compared to the long-term Mean (LTM) for the season over
the northern sector.

The June to August rainfall totals compared to long term average for the season shows that most of the stations in the equatorial sector received totals that were below the long term average for the season (see figure 3b).

Figure 3b: June to August 2004 rainfall compared to the long-term Mean (LTM) for the season over
the equatorial sector.

2.3 Climate stress monitoring

Cumulated water stresses as reflected from cumulative rainfall patterns are shown in figure 4 for some selected stations in the sub-region for the period March to August 2004.

Parts of the sub-region have been under persistence drought for several months. COF14 climate outlook indicates that some of the areas that have been experiencing drought are likely to receive below normal rainfall during September – December period. Some of these areas are further located within the tropics that will expect the next major rainfall season after October-December 2004 to be in March – May 2005. It should also be noted that warm temperatures have also persisted over parts of the region for several months (see Figures 5a and 5b minimum and maximum temperature anomalies for August 2004).
Continued dry and hot conditions of these areas will have severe implication on livestock, food security, water resources, health, and many other economic, environmental and societal factors.

3. Consensus climate outlook for September - December 2004

Consensus seasonal climate outlooks are normally provided by ICPAC, within the framework of the Climate Outlook forums, in collaboration with several international centres including, International Research Institute (USA), before the onset of the major rainfall seasons for timely early warning any impending climate hazards such as drought and floods and the potential impacts. The fourteenth climate outlook forum (COF14) that was held in Nairobi between 23 and 27 August 2004 provided climate projections for September – December 2004 season.

September to December constitutes an important rainfall season over much of the Greater Horn of Africa sub-region. COF14 outlook for the period September to December is given in the cover page. COF14 indicated increased likelihood of near to above-normal rainfall over northeastern Sudan, northern Eritrea, Djibouti, central, western and extreme eastern Ethiopia, southern Sudan, much of Uganda, northeastern and western Tanzania, western Rwanda and Burundi as well southern half and extreme northern parts of Kenya and eastern Somalia. Increased likelihood of near to below-normal rainfall over central Sudan and parts of northern and eastern Ethiopia, northeastern and southwestern Uganda, much of northern Kenya, western Somalia, eastern Rwanda eastern Burundi and much of Tanzania. Climatology is suggested over northern Sudan, much of Eritrea, and Djibouti as well as extreme northern Ethiopia.

COF14 examined the current state of the global climate system and its implications over the GHA region, together with the potential roles of the complex regional systems. Among the principal factors taken into account were the evolution patterns of the Sea Surface Temperature (SST) anomalies over various parts of the global Oceans, particularly over the Indian and Atlantic Oceans, the Quasi-Biennial Oscillation (QBO), monsoons and upper level wind circulation. These and other factors that affect the climate over the Greater Horn of Africa were similarly assessed. These were used in the development of simple empirical models for the September to December (SOND) seasonal rainfall outlook. While deriving the consensus climate outlook for the SOND 2004 season, products from ICPAC / IRI dynamical experimental pilot project were also used, together with those from several other advanced climate centres. The centres whose products were utilized include the National Oceanic and Atmospheric Administration/National Centers for Environmental Prediction (NOAA/NCEP), European Centre for Medium Range Weather Forecasts (ECMWF), United Kingdom Meteorological Office and the International Research Institute for climate prediction (IRI). It should be noted that the current status of seasonal to inter-annual climate modelling allows prediction of spatial and temporal averages that may not fully account for the physical and dynamical factors that influence regional and local climate variability.

4. Climate indicators

4.1 Current sea surface temperatures patterns

Figure 6: Sea surface temperature anomalies for the period August 22 to September 18, 2004 (Courtesy of NOAA/CDC)

The map of Sea Surface Temperature (SST) anomalies for the period from 22 August to 18 September 2004 (Figure 6) indicate that warmer than average Sea Surface Temperatures (SSTs) dominated much of the tropical Atlantic Ocean extending to south-western parts of the Indian Ocean. On the other hand colder that average SSTs were observed eastern, central and northern parts of the Indian Ocean. The statistical and coupled model forecasts by most advanced climate Centres indicate that El-Niño conditions will continue to develop during the next three months. The El-Niño conditions coupled with the prevailing Sea Surface Temperature (SST) patterns over the Atlantic and Indian Ocean are likely to enhance rainfall over the equatorial sector towards the end of the year.

5. Food Security Outlook

From 25 to 27 August 2004, the first Food Security Outlook Forum (FSOF) was convened in Nairobi, Kenya. The (FSOF) was an initiative of the Intergovernmental Authority on Development (IGAD), Igad Climate Predictions and Applications Centre (ICPAC), the World Food Program (WFP), the International Research Institute for Climate Prediction (IRI), the United States Geological Survey (USGS), and the Famine Early Warning Systems Network (FEWS NET). In order to accommodate the probabilistic nature of the forecasts, the precipitation maps were developed for three scenarios: worst case, best case and most likely. The most likely scenarios are included in this report and were used by the countries to create their food security outlooks. The current food security situation as well as sectoral outlooks were interpreted and refined with expert judgment. It was recognized that food security is a product of multiple factors, a number of, which were not included in this FSOF.

The map indicated that areas that are likely to be extremely food insecure include western Sudan, parts of southern and eastern Ethiopia, northern Somalia, northwestern and northeastern Kenya as well as northern Uganda. Highly food insecure areas include southwestern Sudan, much of Eritrea, southern Ethiopia and northeastern Kenya. Moderately food insecure areas include southeastern Sudan, southeastern and coastal areas in Kenya as well as central and southern Somalia (Figure 7).

Figure 7: Regional Food Security Outlook map, GHA, end of December 2004.