Highlights

Rainfall Prediction: Moderately heavy rainfall is predicted for Eastern province and less rainfall is predicted for rest of the country during 29th December-4th January.

Monitored Rainfall: During the last week, the average daily rainfall over Sri Lanka was 0.8 mm & hydro catchment areas received 0.8mm on average and the highest average rainfall (1.6 mm) was received to the Eastern plains of the country. Due to storm (98B), floods and landslides were experienced on 25th Dec in the Kandy district & rainfall in Akurana of 121mm received till 9.30am was among the highest.

Monitored Wind: From 14th – 20th Nov, up to 6m/s of north-easterly winds were experienced at 850mb level over the island. During the last week, strong winds and rough seas were experienced due to storm (98B) over southwest Bay of Bengal.

Monitored Sea and Land Temperature: Sea surface temperature around Sri Lanka was above normal in the Southern half of the country. The land surface temperature remained near normal.

Interpretation

Monitoring

Rainfall: During the last two weeks, there had been very heavy rainfall over Kegalle and Avissawella.

Daily average rainfall in the Met stations for previous week of (15thNovember – 22nd November) =0.8 mm
Rainfall max: 30.5 mm & Rainfall min: 0.0 mm.

Wind: North-easterly winds prevailed in the sea area and around the island last week.

Temperatures: The temperature anomalies were below normal for some parts of the North Central, North Eastern and Central provinces, driven by the warm SST’s.

Storm: The storm ’98B’ originated as a low pressure area over the southwest Bay of Bengal and intensified into the depression (D) on 22nd December. Then it moved west southwestwards and centered at Southwest Bay of Bengal close to east coast of Sri Lanka. Then it cut across the island on 25th December, causing heavy rainfall over Eastern, Central, and Western provinces of Sri Lanka.

Observed & forecast track of storm ’98B’ over the Bay of Bengal during 22nd – 25th December, 2022: IMD

Prediction

Rainfall: During the next week (24th – 30th November), moderately heavy (≥ 40 mm) rainfall is predicted for the Uva, Sabaragamuwa, and Eastern provinces; and less rainfall is expected for the rest of the country.

Temperatures: The temperature will remain below normal for some parts of the Central and Uva provinces during 24th – 30th November.

Teleconnections: La Niña is favored to continue through during the Northern Hemisphere winter (December-February) 2022-23, with a transition to ENSO-neutral favored in February-April 2023 (57% chance).
MJO shall moderately suppress the rainfall during 23rd – 27th November, slightly suppress the rainfall during 28th November – 2nd December, and remain near normal during 3rd – 7th December for Sri Lanka.

Seasonal Precipitation: The precipitation forecast for the December-January-February 2023 season shows a higher tendency for near-normal precipitation to the country.

Terminology for Rainfall Ranges