Sudan Seasonal Monitor

Sudan Meteorological Authority

Federal Ministry of Agriculture and Forestry

Issue 4 July 2008

Summary

•. The rains are showing only moderate northwards progress, in contrast with the early progress during April and May. See Page 1-2.

• The regions of Central Equatoria, Southern Jonglei and Eastern Equatoria in Southern Sudan are ffected by a dry period lasting from mid June to early July. In contrast, Upper Nile saw above average rainfall, a situation extending across to South Kordofan, Blue Nile and Sennar. The little northwards progress of June rainfall led to lower rainfall than expected across large areas of Darfur in the west and in Gedaref in the east. See Page 2-3.

• Early July rainfall was generally better across the country except for the Central Equatoria, southern Jonglei and East Equatoria regions where dry conditions persisted at least until mid July. In this region, the cumulative rainfall since March is about two thirds of the normal and impacts on agriculture may already be noticeable. See Page 3.

• Growing season conditions have been verified in eastern North Kordofan, White Nile, Sennar and Gedaref, but not yet in North Darfur, northern regions of South and West Darfur and western North Kordofan. In eastern East Equatoria no sign yet of growing season conditions. See Page 4.

• Vegetation still at above average levels but with much less intensity than before. Patches of below average vegetation are now appearing as a result of drier conditions in some regions. See Page 5.

• Forecasts for July-September rainfall still indicate above average rainfall but some latest issues indicate lower probabilities of this happening. Given weak northwards progress of the rains, a less optimistic perspective is now advised. See Pages 6.

Seasonal Progress


Fig 1a – Position of the ITF over Africa in July Dekad1 2008 (red) compared to average position (black) and previous position (orange) (Source : CPC).	Fig 1b – Position of the ITCZ over Sudan along the current season compared to a 15 year average. (Source: CPC).

Rainfall in Sudan mostly results from 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, the seasonal progress of the rainy season and of its quality can be evaluated by tracking the ITF. Fig 1(a) shows a map with the latest ITF position, the previous position and the usual position, while Fig 1(b) shows a plot with the average position over Sudan from the beginning of the season.

The current ITF position is currently at its position across Sudan. An initial period (April-May) when the ITF was well north of the average, was followed by a period with very little northwards movement. As a consequence, there has been little northwards progress of rainfall and growing season conditions.

During June, significant rainfall was confined to South-western Sudan, in particular in Western Equatoria, West Bahr-el-Ghazal and Blue Nile (Fig 2a). Elsewhere in Southern Sudan, amounts were low, across south-Eastern regions of Bahr-el-Jabal, lower Jonglei and Eastern Equatoria. In most of Bahr-el-Jbel conditions have been markedly dry from the second week of June onwards.

Low rainfall was also noticed in large areas of Darfur, northeastern regions of Kassala and Gedaref. As a result June rainfall was below average in Greater Darfur, Bahr el Jabel, Gadaref and Kassala.

However, early July brought an improvement in conditions (Fig 2c) : rainfall was good across most regions; in particular in West Equatoria, Greater Bahr-el-Gazal, Upper Nile, South Kordofan, Blue Nile, Sennar and Gedarife good rainfall amounts occurred and the dry conditions that had been predominant during June came to end.

In contrast, conditions stayed dry across most of Greater Darfur, western North Kordofan and also in Bahr-el-Jbel where dryness continued (half of the normal rainfall in early July) and may impact on crops.

The total rainfall from the beginning of the season (Fig 2d) shows above average rainfall across Bahr el Gazal, Warab, Unity and Upper Nile and also in eastern Greater Kordofan, Blue Nile and Sennar, due to better rainfall in mid and late June.

On the other hand, the map clearly shows some persistent dryness in eastern South Sudan, from Bahr-el-Jebel across to East Equatoria and southern Jonglei.

A more in-depth evaluation of the effect of rainfall can be made by comparing it to the water demand imposed by the environmental conditions (i.e. temperature, humidity, solar insolation and wind levels). This comparison between rainfall and environmental water demand is expressed by a ratio between the two, the Moisture Index (MI). So higher (lower) MI values correspond to wetter (drier) conditions.

The MI is useful because you can use it to estimate if conditions suitable for crop planting have occurred and if crops have their water requirements satisfied.

The Moisture Index (MI) in Sudan during this period shows high moisture values in South Kordofan and northern regions of Southern Sudan, Upper Nile, as a result of good rainfall.

There has been little northwards progress of suitable moisture conditions, although in early July good moisture conditions spread from southeastern North Kodofan across White Nile into Sennar and Gedaref.

The maps also show clearly the dry conditions that have prevailed in East Equatoria and Bahr-el-Jbel as a consequence of low rainfall.

To detect the onset of the growing season (i.e. occurrence of suitable conditions for planting and early crop development), we identify areas where the MI exceeds a value of 35% (which corresponds to the water needs of a crop in the first stages of development) for at least two 10 day periods. Fig 4 shows the dates on which the growing season is estimated to have started across Sudan :

Season well under way across Southern Sudan, except in the eastern half of Eastern Equatoria, where moisture conditions have not been good enough for the onset of growing season. The region is predominantly a pastoral region and the current situation may pose problems to this livelihood if moisture conditions do not improve.

Growing season conditions made some progress in Southern Darfur and also in southern half of West Darfur. In North Kordofan, conditions became suitable in the southeastern region of the state and have spread across southern half of White Nile, Sennar and most of Gedaref. This will allow a timely start of the agricultural activities.

Elsewhere no progress has been made and conditions need to improve over the next couple of weeks for a timely start of the agricultural season for subsistence farmers.

In general the start of the growing season is occurring later than in 2007 across most of the country, but in particular in North Darfur and North Kordofan and other northern areas, where growing season conditions in 2007 started in late June.

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.

Continued vegetation progress in lower South Darfur, South Kordofan and eastern regions of Blue Nile and Sennar. Northwards progress was very moderate in line with little northwards progress of the rains.

Vegetation development continued in Southern Sudan approaching the seasonal maximum levels – however, in East Equatoria further green up has been very moderate, with lower development than in 2007, though this was an exceptional year.

Above average vegetation is still dominant across Southern Sudan but becoming closer to average. Vegetation is still much above average in Jonglei, possibly due to maintenance of good rainfalls in the mountains along the border and flow from higher ground in Ethiopia.

Most of this is judged to be due to natural vegetation growth. Crops are unlikely to be doing so well, specially in Central and Eastern Equatoria where conditions are on average and below average areas begin to appear.

In northern Sudan significant developmente due to the effect of rainfall can be seen in Blue Nile and Sennar but South Kordofan is showing a tendency to below average values.

July-August-September (JAS) is the crucial period for most crops in Sudan, in particular for the northern regions. Forecasts for JAS rainfall have been prepared in May by SMA while international institutions updated their JAS forecasts in June.

Fig 6a shows the SMA forecast for June-September rainfall. Fig 6b displays a forecast for JAS 2008 rainfall from IRI (International Research Institute).and Fig 7 a forecast from the ECMWF, European Centre for Medium-range Weather Forecasts. The general consensus is still of a wetter than average season across most of the country, though with conditions close to normal in Southern Sudan.

However, it is noticeable that the June updating of the ECMWF forecast (Fig 7), has considerably moderated these indications towards closer to average conditions than a month ago. Considering the current ITF evolution (see page 1), the forecasts may have to be viewed with some reservations.