Seasonal Rainfall Forecast for March to May 2011

(a) Overview

Following the conclusion of the 27th Climate Outlook Forum for the Greater Horn of Africa held in Arusha, Tanzania on 28th February 2011, the international, regional and national scientists reviewed the state of the global climate systems and their implications on the seasonal climate of the sub-region including the influence of sea surface temperature anomalies over the tropical Pacific, Atlantic and Indian Oceans on the evolution of rainfall in the GHA region. Guidance products from the World Meteorological Organisation’s Global Producing Centres and other seasonal climate prediction centres were also assessed. These inputs were combined using expert analysis and interpretation to obtain forecast probabilities for the evolution of regional rainfall during the period March to May 2011.

It was observed that the major physical conditions that are likely to influence the Uganda’s weather for the forecast period of March to May 2011 are current but declining moderate La Niña conditions (building up of a large pool of unusually cold waters in large parts of the eastern and central equatorial Pacific Ocean) which are likely to continue throughout the forecast period of March to May 2011. Other regional systems that are likely Uganda’s weather include the Sea Surface.

Based on the above considerations as well as details of the climatology, model forecasts, trends of the ongoing weather patterns, and the physical features of the different regions of the country, the Department of Meteorology has come up with the following forecast:

(b) General Forecast

Overall, there is increased likelihood of near normal to below normal rainfall over most parts of the northern sector (areas running from west Nile through Masindi, Lira, Soroti to Karamoja) while the southern sector including areas around Lake Victoria extending from Busia to south-western Uganda are expected to experience near normal to above normal rainfall during the first rainy season of March-May 2011. (See figure 2 below).   

(c) Detailed region by region forecast with onset and cessation dates for MAM 2011 

  1. i) Eastern region
  • Eastern Lake Victoria and South Eastern: (Jinja, Kamuli, Iganga, Mayuge, Bugiri, Busia and Tororo).

The region is currently experiencing dry spells which are likely to continue up to around mid March when the onset of steady rains is expected. The peak of the seasonal rains is expected around early April through early May. Overall this region has a high chance of receiving near normal to above normal rains.

  • Eastern Central:  (Pallisa, Mbale, Manafa, Sironko, Kapchorwa, Kumi, Kaberamaido, Soroti).

This region has been experiencing a rather prolonged dry spell which is now easing up as steady rains get established. The steady rains are expected to intensify with peak rains occurring around mid April to mid May.  Thereafter the rains are expected to reduce sharply by late May. A prolonged dry spell is expected during the month of June.  Overall the region is expected to experience near normal to above normal rainfall.

  • North Eastern region:  (Katakwi, Moroto, Kotido, Nakapiripiriti).

The region has been experiencing a rather severe prolonged dry season. The onset of steady rains is expected early April. Overall near normal to below normal rainfall is expected in this region. 

  1. ii) Central Northern Region
  • Eastern Parts: (Lira, Pader, Kitgum)

The region has been mainly dry with occasional outbreaks of light rain showers.  The onset of steady rains is expected around late March / early April with the peak expected around late April/early May.  Overall near normal to below rainfall is expected during this season.

  • Central Northern Parts : (Amuru, Gulu, Apac)

Currently the area is mainly dry and the onset of steady rains is expected around late March to early April.  The steady rains are expected to increase with the peak being experienced around late April to mid May.  This will be followed by a moderate relaxation during the month of June.  Normal to below normal rainfall is expected to prevail during this season.

iii) Western Region

  • North Western: (Moyo, Yumbe, Adjumani, Arua, Terego, Zombo and Nebbi)

This region has been mainly dry with occasional outbreaks of light rain showers. The onset is expected late March to early April and relaxation around mid June. There is a high chance of this region receiving near normal to below normal rainfall during this season.

  • Western Central: (Masindi, Hoima, Kibaale, Kyenjojo, Kamwenge, Kabarole and Bundibugyo)

The region is currently experiencing dry spells with occasional outbreaks of light rain. The steady rains are expected around mid March. Peak rains are expected around early April to mid May.  Rainfall is expected to relax late May with the cessation occurring early June.

  • South Western: (Kasese, Bushenyi, Rukungiri, Kanungu, Ibanda, Mbarara, Kiruhura, Ntungamo, Kisoro, Kabale)

Onset of seasonal rains is getting established in this region. The peak of the steady rains is expected late March to early April and the cessation late April.  Overall the region is expected to receive near normal to above normal rainfall amount during this season.

  1. iv) Lake Victoria Basin and Central areas
  • Central and Western Lake Victoria Basin: (Kalangala, Kampala, Wakiso,            Entebbe, South Mpigi, Eastern Masaka, Mityana)

This region is currently experiencing sporadic out breaks of light showers and thunderstorms but steady rains are expected mid March. The rains are expected to intensify with the peak occurring around late April to early May. The cassation is expected around early June. Overall, there are high chances of normal to above normal rainfall.

  • Western Parts of Central: (Nakasongola, Luwero, Kiboga, Mubende, Sembabule, Western Masaka, Lyantonde,   Rakai)

This region is currently experiencing prolonged dry spells. The onset of seasonal rains is expected around mid March. The rains are expected to intensify with the peak occurring around April. The cassation is expected around mid May. Overall, there are high chances of normal to above normal rainfall over the eastern parts of this region and normal to below normal over the western parts. 

  • Eastern parts of Central: (Mukono, Buikwe and Kayunga)

This region is currently experiencing dry spells with occasional outbreaks of showers and thunderstorms signifying the onset of steady rains. The steady rains are expected to intensify with the peak occurring around mid April.  Thereafter, the rains are expected to relax with cessation occurring mid- June. Overall, near normal to above normal rainfall is expected over this region.

3.0 The implications of the current forecast

  • The performance of rains in the areas that are expected to experience below normal areas will be very poor.
  • The Semi-Arid areas of Karamoja and other areas that are currently experiencing dry conditions are likely to receive deficient rainfall once again. Consequently, some of the disasters that have been associated with the drought conditions are likely to continue in some of these areas.
  • The southern sector of the country is expected to receive enhanced rains that may increase agricultural production
  • The rainfall is expected to start between the first and second week of March over the western parts of the country and spreads to other areas during the second to third week of March 2011.
  • It should be noted that areas expected to receive near normal to below normal rainfall does not mean that they will not receive rainfall at all. It means that they will receive rainfall below the long term mean (Thresholds are indicated in explanatory notes to terminology in Appendix 1)
  • It should also be noted that localised episodic flash flood events may also be observed in areas that are expected to receive below normal rainfall as a result of sporadic heavy down pours and similarly, poor rainfall distribution may occur in localised areas expected to receive above normal rainfall.
    1. Expected impacts

    In general, the occurrence of this poor rainfall performance especially over the Northern and Eastern parts of the country is likely to have some implications on various socio-economic activities in the regions.

    The negative potential impacts include: Failure of crops; lower than normal water levels in dams and lakes which can lead to severe power rationing and the associated large economic losses; rural-urban water shortages for both domestic and industrial use; in pastoral areas lack of pasture and water for animals; shortages in food production and supply in some areas leading to famine and the associated health problems such as malnutrition among others. However it should be noted that many parts of the country have had normal to above normal rains during the past season. This means that the soil moisture is still high in many places which will affect the severity of the potential impacts.

    1. Advisories

    The regions that are expecting enhanced rainfall (near normal to above normal rainfall) should use this chance to improve on agricultural activities. The farmers are advised to make use of this season by optimizing crop yield through appropriate land-use management. They should be encouraged to plant enough food that will also cater for the drought stricken areas. The households with some food stocks in areas that are expected to experience below normal rainfall are urged to use the food stocks sparingly and ensure appropriate food storage practices to avoid losses especially through pest attacks.

    • Crop failure is expected in the regions where below normal rains are expected. In such areas, timely planting of crops that take short duration to mature and tolerant to drought conditions is encouraged. Farmers are therefore advised to approach their nearest extension workers for advice on the appropriate stockists in their locality to plant during such suppressed rainfall season.
    • Even in areas where below normal rains are expected, heavy down pours of rain and flash floods are likely to be experienced in some days.  Farmers are advised to prepare to harvest this water. Roof water harvesting for home consumption, and ground water harvesting into gardens, dams and valley tanks for livestock and sustaining crop production is encouraged. The practice of drip irrigation is encouraged where possible on crops especially vegetables in back yard gardens. Farmers are advised to approach their nearest extension workers for the appropriate water harvesting technologies to use.
    • In conclusion, the expected poor rainfall performance over most areas is likely to increase the level of vulnerability of communities in disaster prone areas far beyond their coping capacities if this prediction is not integrated into agriculture and food security, and other disaster management programmes of the most vulnerable sectors in the country. For instance, it may be recalled that the 1999/2000 La Niña-related drought had severe impacts on both human and animal lives and many social-economic activities. The predicted scenario requires action in sufficient time and in an appropriate manner so as to reduce the possibility of personal injury, loss of life and damage to property. Appropriate coping mechanisms should therefore be put in place to see the vulnerable communities survive through this difficult period until normal conditions are realized.

Note:  This forecast will be updated monthly and as when necessary and the Department will keep users informed of any new developments.

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