Summary

·         Rainbearing airmasses are moving north faster than usual and are now 200Km north of the average, leading to an earlier than usual beginning of the rains across Sudan. See Page 1.

·         So far, significant rainfall is confined to Southern Sudan, with good rainfalls in the Yei region, borders with Uganda and southeastern Jonglei. However, Central Equatoria has registered little rainfall, with the totals so far at 40% of the average. See Page 2.

·         Unusually, rainfall has been reported at Gadaref and Kassala and also Kosti and Sennar during April, due to the more northerly than usual position of the rainfall systems. This is not expected to continue. See Page 2.

·         Vegetation levels are increasing in Southern Sudan to levels above average in the areas of better rainfall. Elsewhere, situation is normal. See Pages 3 and 4.

·         The wheat crop harvest is now in and preliminary figures are becoming available; favourable temperature regime, increases in area planted and objective estimates of yields, led to a more accurate estimate of 500,000 to 600,000MT for the 2008 wheat production. See Pages 4 and 5.

·         La Niña conditions are now weakening and decaying over the next 2-3 months to neutral conditions which are expected to continue until early 2009. See Page  5.

·         Below average rainfall is forecast in Southern Sudan for March-April-May. Elsewhere, early season rainfall is forecast to be above average, but amounts are usually of little significance for the seasonal totals and for the crops grown. See Page 6

·         Forecasts for July-August-September from diferent sources are not fully consistent, but on balance, a wetter than average JAS period is judged to be the most likely scenario. Initial perspectives for the agricultural season are favourable, but require careful monitoring in the forthcoming months. See Pages 6 and 7.

Seasonal Progress

Rainfall in Sudan mostly results from a northwards movement of humid air masses from March to August and their southwards retreat from September to November. At their northernmost reach, these humid air masses meet with drier and warmer air to form the InterTropical Front (ITF). Since the rains follow south of the ITF, tracking the ITF through the season provides a quick evaluation of the seasonal progress of the rainy season and of its quality.

Fig 1 shows a map with the latest ITF position. Current position of the ITF is markedly northwards of its average position and is now 200Km North of the usual. The difference is more marked in the East of Sudan. As a consequence, the rainfall season is starting earlier than usual and there has been already rainfall in Gedaref-Kassala region in early April and in central Sudan in mid April.

March and Early April Rainfall in Sudan

During March and early April, significant rainfall was confined to Southern Sudan. Here, higher amounts were registered in the Yei region and in southeastern Jonglei with low amounts in Central Equatoria (see Fig 2a,b). Rainfall has been significantly below average in Central Equatoria – about 40% of the average. In West Equatoria and northeastern Jonglei, rainfall is on or above average (see Fig 2c).

The delay in the start of the rainfall season in Central Equatoria is expected to lead to some delay in the start of the agricultural activities, but given the length of growing season periods here, there is plenty of time for recovery. Elsewhere, situation is normal.

 Unusually, in early and mid April, rainfall has been reported at Gedaref and Kassala and also White Nile and Sennar regions. This very early rainfall is a consequence of the rainbearing cloud systems being in a more northerly position than usual. However, this unusual situation is not expected to continue.

Vegetation Status

Vegetation condition and development are assessed by means of the NDVI (Normalized Difference Vegetation Index) – this is a satellite derived parameter which responds (almost) uniquely to vegetation and is available on a global scale every ten days.

Higher greenness in West Equatoria, along the border with Uganda, highlands of East Equatoria and southeastern Jonglei. Wetlands along the White Nile also show high greenness (as usual), as a consequence of rainfall during March and early April. Fig 3a,b shows the increase in vegetation from early March to early April in Southern Sudan, and a decrease in the irrigated schemes (Gezira and New Halfa) due to the end of the Winter Season crops.

In terms of variations from average, above average vegetation is noticeable in West Equatoria, along the borders with Uganda and southwest East Equatoria, pointing to an earlier than usual start of the growing season (see Fig 3c).

So far, we don’t see impacts of lower than average rainfall on vegetation development. However, greenness results from natural vegetation, and negative impacts on early agricultural activities can still be present in the Central Equatoria’s Juba region.

Perspectives on the Wheat Crop

The winter wheat crop is in the final stages of harvest and final production numbers will be available by the  end of April, early May. Wheat is grown as an irrigated crop during Winter (November to March) and the major producing areas (in decreasing order of importance) are the Gezira scheme (Gezira state), and several irrigation perimeters along the Nile in Northern State (Dongola and southwards along the Nile), River Nile State, White Nile State and Kassala state (in the Halfa-el-Jadida irrigation scheme). Other wheat growing areas are now appearing (e.g. Sennar state) but so far make very small contributions to the national total.

The key meteorological factor influencing wheat production is temperature, with higher than normal temperatures during the development stage (early January to mid February) leading to poorer yields. Temperatures this season at meteorological stations within or near the wheat producing areas (see Fig 4a-e) show that December was warmer than usual across all regions; this was followed by colder than average January and February in the more northern locations (Dongola, Abu Hamed) and close to average temperatures elsewhere. March was again warmer than usual but this is of little significance.

These normal meteorological conditions were coupled with good availability of inputs (fuel, fertilizer) and good levels of finance. These factors are behind expectations of good yields across all producing regions.

For this season, the FAO-implemented, EU funded SIFSIA project supported field campaigns of area and yield measurement (crop-cutting campaigns) for the Winter wheat crop (and also the localized winter crop of sorghum and millet in Gash and Tokar), which had last taken place in 2003.

The field campaigns obtained area estimates for Northern and River Nile states only, the remaining regions relying on figures supplied by the state’s MoAs and the Gezira Scheme management. For yield, the campaigns covered the major wheat producing regions with the exception of the Gezira Scheme, where estimates are the responsibility of its management. These field campaigns will result in more accurate figures for crop area and particularly for crop yield. Final results are due by late April / early May and will be published in the next issue.

According to preliminary results (see table right), there is no significant increase in area planted at the country level, but there are considerable variations from region to region : while the Gezira scheme reports a large (+40%) increase in planted area, Northern and River Nile states report a considerable drop (-48%). However, this year’s figures for these two states are based on actual field data, while last year’s are based on subjective indications by the state MoA – the drop may be more an adjustment towards more realistic values.

Elsewhere, wheat areas continue to expand : the Halfa-el-Jadida scheme increased area planted from 5,000 to 33,000fd, while a number of new regions are now planting wheat – in Sennar state, in the Suki irrigation scheme (Sennar state as well) and in Khartoum state. Areas are so far small (22,000fd in total) but may well increase further given current level of incentives for wheat growing. Across all regions harvested areas are about 95% of planted areas (as typical for irrigated conditions).

Yields last season were reported to vary between 1.2MT/fd (Northern State) to 0.75MT/fd in Kosti and Halfa-el-Jadida (they tend to be higher in the areas with cooler Winters). Again these were based on subjective estimates from state and scheme authorrities. Preliminary results from current season field campaigns point to much lower yields (0.6-0.9MT/fd), while initial claims from state and scheme authorities were that yields this season would be better than previous years.

All things considered, relying on preliminary numbers from the field campaigns, the total wheat production for 2007-2008 is expected to be around 500,000 to 600,000MT. A proper comparison with previous years is difficult given the widely different approaches used in the estimations, but this season’s production is expected to have been the highest so far.

Detailed results for the different regions will be published in the next Bulletin.

Seasonal Perspectives

Current El Niño / La Niña Outlook

El Niño (and La Niña) events are disruptions of the ocean-atmosphere system in the Intertropical Pacific which can cause large scale changes in wind circulation and sea surface temperature, and lead to a variety of impacts on rainfall and temperature distribution across the globe.

Presently La Niña conditions still continue from the peak verified in late 2007 (a La Niña year), but conditions are now weakening and will decay to neutral over the next 2-3 months. Forecasts (Fig 5) point to a maintenance of neutral conditions until early 2009.

Note that El Niño – La Niña effects on the climate of Sudan are not known in detail but are judged to be weaker than in other areas such as Southern Africa and Kenya-Tanzania.

Rainfall Outlook

March-April-May 2008 Rainfall

There are a variety of methodologies and models that use tropical east Pacific sea surface temperature (SST) patterns as input to predict/forecast long term (1 to 6 month) changes to rainfall and temperature regimes over wide areas of the globe.

SMA published its seasonal forecast for the rainfall in March-April-May (Fig 6). This early season rainfall is expected to be below average in Southern Sudan with only 20% chance of it being above average. Elsewhere, early season rainfall is forecast to be above average, but note that rainfall during this period in the northern half of the country is of little significance for the seasonal totals and for the crops grown in the region. So far in qualitative terms this forecast is in broad agreement with the actual situation. 

For this same period and the next (April-June), other sources (IRI) indicate average conditions throughout the country.

July-August-September 2008 Rainfall

This period is the crucial one for most crops in Sudan, in particular for the northern regions. There are forecasts available prepared in March for this period from a variety of sources. However, forecasts made at such long ranges have low skill and provide only general guidance. As a result, it is frequent to find conflicting information and this is the case for this season.

Fig 7a,b displays forecasts for JAS 2008 rainfall from IRI (International Research Institute) and CPC/NASA (Climate Prediction Centre). As can be seen, they forecast opposite situations, with the former pointing to a wetter than average season and the latter to a drier than average situation. In the absence of data on their performance, it is not possible to select the best advice, though IRI forecasts have performed subjectively well in the past couple of seasons.

A forecast from a third source (ECMWF, European Centre for Medium-range Weather Forecasts) is shown in Fig 8. This one agrees with the IRI forecast in that it forecasts a wetter than average JAS period across Sudan (and other areas). 

On balance, this Bulletin is inclined to align itself with a scenario of a wetter than average season. If this is verified it will be the fourth season in a row with generally good rainfall and good agricultural production output.

Forecasts for this period are periodically updated and the predicted situation may still change. In any case, actual crop-related quality of the rainfall season is influenced by a range of other factors such as the timing and distribution of rainfall amounts through the season.