Media Center
Climate Bulletin for Sri Lanka (Week of 29 September – 06 October 2023)
Highlights
Rainfall Prediction: Heavy rainfall (≥ 115 mm) is predicted for the Southern, Sabaragamuwa, Western, Uva, Central provinces and fairly heavy rainfall (85 mm) is predicted for the North Western, Eastern provinces during 26 Sep – 2 Oct.
Monitored Rainfall: During the last week, average daily rainfall over Sri Lanka was 13.3 mm and hydro catchment areas received 5.3 mm. Highest average rainfall of 17.6 mm/day received Western plains.
Monitored and Predicted Wind: During 27 Sep – 3 Oct, up to 15 m/s of west-southwesterly winds are expected at 850 mb (1.5 km).
Monitored Sea and Land Temperature: Sea surface temperature around Sri Lanka was 0.25 – 1.5ºC above normal. From 18 – 25 Sep, maximum daily temperature was recorded in Polonnaruwa (38.3ºC) and Vavuniya (36.9ºC).
Interpretation
Monitoring
Rainfall: During the last two weeks, there had been very heavy rainfall over the following area: Galle
Daily Average Rainfall in the Met stations for previous week of (18 th September – 25 th September) = 13.3 mm
Maximum Daily Rainfall: 95.0 mm & Minimum Daily Rainfall: 0.0 mm.
Wind: Northwest-southwesterly winds prevailed in the sea area and around the island last week.
Temperatures: The temperature anomalies were above normal for some parts of the Northern and Uva provinces of the country driven by the warm SST’s.
Prediction
Rainfall: During the next week (26 th September – 2 nd October), heavy rainfall (≥ 115 mm) is predicted for the Southern, Sabaragamuwa, Western, Uva, and Central provinces and fairly heavy rainfall (85 mm) is predicted for the North Western and Eastern provinces and less rainfall is predicted for the rest of the country.
Temperatures: The temperature will remain above normal for some parts of the Northern and Eastern provinces and below normal for some parts of the Central province during 27 th September – 3 rd October.
Teleconnections: A positive Dipole Mode has set in across the Indian Ocean since 8 th of June. MJO shall near neutral the rainfall during 26 th September – 10 th October for Sri Lanka.
Seasonal Precipitation: The precipitation forecast for the October-November-December 2023 season shows a 50 – 60% tendency toward 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 |
