Media Center
Climate Bulletin for Sri Lanka (Week of 22 September – 29 September 2023)
Highlights
Rainfall Prediction: Heavy rainfall (≥ 115 mm) is predicted for the Sabaragamuwa, Southern, Western provinces and fairly heavy rainfall (≥ 65 mm) is predicted for the Uva, Central, North Western provinces during 21 – 27 Sep.
Monitored Rainfall: During the last week, average daily rainfall over Sri Lanka was 21.1 mm and hydro catchment areas received 6.7 mm. Highest average rainfall of 17.9 mm/day received Western plains.
Monitored and Predicted Wind: From 12 – 18 Sep, up to 15 m/s of west-southwesterly winds were at 850 mb (1.5 km). During 22 – 28 Sep, up to 10 m/s of northwest-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 13 – 20 Sep, maximum daily temperature was recorded in Polonnaruwa (38.3ºC) and Mullaitivu (37.0ºC).
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 (13th September – 20th September) = 21.1 mm
Maximum Daily Rainfall: 95.0 mm & Minimum Daily Rainfall: 0.0 mm.
Wind: West-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 (21st September – 27th September), heavy rainfall (≥ 115 mm) is predicted for the Southern, Sabaragamuwa, and Western provinces and fairly heavy rainfall (≥ 65 mm) is predicted for the Uva, Central, and North Western provinces and less rainfall is predicted for the rest of the country.
Temperatures: The temperature will remain above normal for some parts of the Eastern, Northern, North Central, and Uva provinces and below normal for some parts of the Central province during 22nd September – 28th September.
Teleconnections: A positive Dipole Mode has set in across the Indian Ocean since 8th of June.
MJO shall near neutral the rainfall during 21st September – 5th 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 |
