Media Center
Climate Bulletin for Sri Lanka (Week of 01 September – 08 September 2023)
Highlights
Rainfall Prediction: Very heavy rainfall (>135mm) is predicted for the Southern Province: heavy rainfall (>100mm) is predicted for Sabaragamuwa, Western, Uva, Central and Eastern provinces from 31 Aug – 6 Sept
Monitored Rainfall: During the last week, average daily rainfall over Sri Lanka was ‘light’ (2.6 mm) and hydro catchment areas received ‘light’ (4.9 mm) showers. Overall, 33% drop in rainfall during the August.
Monitored and Predicted Wind: From 15 – 21 Aug, up to 8 m/s of southwesterly winds were at 850 mb (1.5 km). During 1 – 7 Sept, up to 15 m/s of westerly -southwesterly winds are expected at 850 mb (1.5 km).
Monitored Sea and Land Temperature: Sea surface temperature around Sri Lanka was 0.5 – 2ºC above normal. From 22 – 29 Aug, maximum daily temperature was recorded in Vavuniya (38.3ºC), and Polonnaruwa (37.7ºC)
Interpretation
Monitoring
Rainfall: During the last two weeks, there had been heavy rainfall over the following area: Ratnapura. Daily Average Rainfall in the Met stations for previous week of (22th August – 29th August) = 2.6 mm. Maximum Daily Rainfall: 101.3 mm & Minimum Daily Rainfall: 0.0 mm.
Wind: Southwesterly winds prevailed in the sea area and around the island last week.
Temperatures: The temperature anomalies were above normal for the entire island and expect provinces of the country driven by the warm SST’s.
Prediction
Rainfall: During the next week (31st August – 6th September), very heavy rainfall (>135mm) is predicted for the Southern Province: heavy rainfall (>100mm) is predicted for Sabaragamuwa, Western, Uva, Central and Eastern provinces; fairly heavy rainfall (55-85 mm) is for North Western and North Central provinces and less rainfall is predicted for the rest of the country.
Temperatures: Temperatures:The temperature anomalies were above normal for the entire island and except for some parts of the northern province of the country driven by the warm SST’s.
Teleconnections: A positive Dipole Mode has set in across the Indian Ocean since 8th of June. MJO shall near neutral the rainfall during 31st August – 14th September for Sri Lanka
Seasonal Precipitation: The precipitation forecast for the September-October-November, 2023 season shows above normal precipitation for the country.
Terminology for Rainfall Ranges
| Rainfall (During 24 hours of the period) | |
| Light Showers | Less than 12.5 mm |
| Light to Moderate | Between 12.5 mm and 25 mm |
| Moderate | Between 25 mm and 50 mm |
| Fairly Heavy | Between 50 mm and 100 mm |
| Heavy | Between 100 mm and 150 mm |
| Very Heavy | More than 150 mm |
