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There is a moderate likelihood that above normal 2024 Gu rains will be observed over Somalia but with high week-to-week variability
Forecast for 2024 Gu “Long Rains” Season
Somalia’s Gu (April-May-June) is the main wet season in the country, and is critical in supporting agricultural activities and replenishing water and pasture. Traditionally, the season begins as early as the second half of March just after the end of the dry and hot Jilal season. The Gu rains intensify in April with the onset progressing northwards and eastwards almost mimicking the south-to-north movement of the Inter Tropical Convergence Zone (ITCZ) that follows the position of the overhead Sun. Gu rainfall cessation occurs in June in most parts of the country, with the north-eastern coastline receiving the least amount of rainfall during this season.
According to the Seasonal Climate Forecast issued by IGAD’s Climate Prediction and Applications Centre (ICPAC), there is a 55 % likelihood that above normal rainfall (wetter than normal conditions) will be observed over most parts of Somalia as is evidenced by the green coloration shown in Map 1. In the south these above normal rains are likely over Gedo, Bay, and most parts of Bakool regions. In the north, chances of above normal Gu rains are particularly high over Bari, Nugaal, Sool, Sanaag and Awdal regions, Hargeisa district in Woqooyi Galbeed region, and the southern parts of Togdheer region. Above normal rains are also likely over Mudug and Galgaduud regions in the central parts of the country. As shown by the light green coloration in Map 1, there is 40 – 50 % likelihood above normal rains over Hiraan region and extensive coastal parts of the following regions: Lower Juba, Middle Juba, and Lower Shabelle.
However, due to the poor predictability of the Gu rain season, the forecast is expected to have high spatial and temporal variability. Further, the rainfall forecasts categories vary over regions; 170 mm and 195 mm thresholds are applicable over Somalia. It is worth noting that this forecast is designed for a regional audience that addresses the rainfall totals summed over the three-month period from March to May 2024.
Expected Rainfall Onset Dates
Based on ICPAC’s projection using daily rainfall forecasts derived from five Global Climate Models, there is a 50 % of an early onset of Gu rains over most parts of south and western Somalia. An early onset is also likely over the northwestern Somalia particularly the northern parts of Woqooyi Galbeed.
A normal Gu rainfall onset is expected over most parts of Puntland. Generally, the Gu rains are likely to begin during the first week of April over the western parts of Gedo and Lower Juba regions and the uppermost catchments of Juba and Shabelle Rivers over Ethiopian Highlands progressing eastwards with the last onset over Bari region in the first week of May.
The predicted actual rainfall start dates (Map 2) are as follows: Gedo (April 1), Lower Juba (April 6), Middle Juba (April 11), Bay (April 11), Bakool (April 11), Woqooyi Galbeed (April 11), Hiraan (April 16), Lower Shabelle (April 16), Middle Shabelle (April 21), Awdal and Togdheer regions (April 21), Galmudug and Sool-Sanaag (April 26), and Bari (May 1).
It is worth noting that cloudiness and isolated moderate to heavy rains may be observed earlier than the forecast operational onset dates particularly over the south and western parts of Somalia and in the uppermost catchments of Juba and Shabelle Rivers in Ethiopian Highlands.