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MARCH TO MAY 2020 SEASONAL RAINFALL OUTLOOK OVER UGANDA
1. Rainfall performance for September 2019 to January 2020
Uganda National Meteorological Authority (UNMA) released the Seasonal Climate Outlook for the September to December (SOND) 2019 period on 9th September 2019. It indicated that much of Uganda was expected to receive enhanced rainfall (Above Normal) that could result into disasters such as landslides and floods especially in the areas that are prone to such disasters. The forecast was perfectly correct. From September 2019 to January 2020, several districts in Uganda have been experiencing occasional outbreaks of heavy showers and thunderstorms that resulted into flash floods in most urban areas and landslides in hilly areas.
The spatial distribution of the observed rainfall in terms of total in (mm) and deviation from average rainfall over the country for the months of September 2019 to January 2020 with their corresponding statistics are indicated in the Annex 1.
The SOND 2019 rains were associated with positive Indian Ocean Dipole (IOD), that aided higher evaporation, and also created a low pressure zone in western part of the Indian Ocean and hence allowing in reversal winds from the colder parts of Indian Ocean to transport moist air inwards over the continent near the equator, strengthening the ITCZ and leading to larger and more widespread storm clouds that resulted into wetter conditions across many East African countries including Uganda. On a positive note, these rains increased water levels for hydro-power generation, improved pasture for livestock and wild life, and increased soil moisture for agricultural activities over most parts of the country. On a negative note, they led to landslides and floods to some areas that killed people and damaged property in some parts of the country especially Bududa, Sironko, and Bundibugyo Districts.
2. Rainfall outlook for March to May 2020
March-April-May (MAM) constitutes the first major rainfall season over Uganda. During the 54th Climate Outlook Forum for the Greater Horn of Africa (GHACOF54) which was held at Pride Inn Paradise Beach Hotel in Mombasa, Kenya from 27th to 29th January 2020, the National, Regional and International Climate Scientists reviewed the state of the global climate system and its implications on the seasonal rainfall over the region. It was observed that the major physical conditions likely to influence the weather conditions over Uganda for the forecast period of March to May 2020 are as follows: -
i) The current and evolving Sea Surface Temperature (SST) anomalies over global oceans, specifically the increased probability for neutral El Nino Southern Oscillation(ENSO) conditions over equatorial Pacific and Indian Ocean Dipole (IOD) phases through the March to May 2020 period;
ii) Intra-seasonal variations such as the influence of Madden Julian Oscillations (MJO) which are most significant over the region;
iii) The influence of regional circulation patterns, topographical features and large inland water bodies;
Based on the above considerations as well as details of the climatology of Uganda and scientific tools for climate analysis and prediction, Uganda National Meteorological Authority (UNMA) has come up with the following rainfall outlook:
Overall, there is an increased likelihood of near normal to above normal (wetter than average) rainfall over several parts of the country. The onset of the seasonal rains is expected to be early in South-western (late February) with a gradual progression in other parts of the country. The rainfall onset over the Eastern, Northern and North-eastern Uganda is expected to get established around mid-March to early April. The MAM2020 rainfall season is highly expected to be associated with thunderstorm activity that is likely to be characterized by lightning, strong winds and hailstones in some parts of the country.
2.1 South and Central Western Uganda
2.1.1 South Western: (Kisoro, Kabale, Rubanda, Rukiga, Rwampara, Kazo, Rukungiri, Kanungu, Ntungamo, Mbarara, Kiruhura, Isingiro, Ibanda, Kitagwenda, Bushenyi, Buhweju, Mitooma, Sheema, Rubirizi and Kasese) districts.
The region has been experiencing dry conditions in most areas punctuated by unseasonal rains since January. The onset of the rains is expected around late February to early March. The peak of the rains is expected around early to midApril and cessation around late May. Overall, the region is expected to receive above normal rainfall (exceeding their average rainfall).
2.1.2 Western Central: (Bundibugyo, Ntoroko, Kabarole, Kyenjojo, Kyegegwa, Kamwenge, Kibaale, Kikuube, Bunyagabu, Kakumiro, Kagadi, Hoima, Buliisa, Masindi, Kiryandongo) districts
The region has been experiencing isolated light showers and dry conditions since January. The onset of seasonal rains associated with isolated outbreaks of light showers and thunderstorms is expected in around early to mid-March. Thereafter, steady rains are expected to get established with the peak of the rains expected during the month of April. Cessation of the seasonal rains is expected around late May to early June. Overall, there are high chances for the region to receive near normal rains with a slight tendency to above normal rains.
2.2 Central Region and Lake Victoria Basin
2.2.1 Western areas of Central region: (Nakasongola, Luwero, Kyankwanzi, Kakumiro, Kasanda, Nakaseke, Kiboga, Mubende, Sembabule, Western Masaka, Lyantonde, Kyotera and Rakai) districts The region has been experiencing isolated rains and some dry conditions since January. The onset of seasonal rainfall associated with occasional outbreaks of showers and thunderstorms is expected around early to mid-March. The peak of the rains is expected to occur around mid to end of April. While the Cessation of the seasonal rains is expected to occur around late May to early June. Overall, there are high chances of near normal rainfall conditions.
2.2.2 Central and Western Lake Victoria region (Kalangala, Kampala, Wakiso, Eastern Masaka, Lwengo, Mpigi, Butambala, Kalungu, Bukomansimbi, Gomba, and Mityana) districts The region has been experiencing off seasonal rainfall over several areas since January. The onset of the rains associated with isolated outbreaks of showers and thunderstorms is expected to get established around early to mid-March. The peak of the rains is expected to occur around early to mid-April with cessation around late May. Overall, there are high chances for most of the areas to receive near normal with the tendency to above normal rainfall during this season