Highlights

Rainfall Prediction: Fairly heavy (≥75 mm) rainfall is predicted for the Eastern, Western, Sabaragamuwa, Uva, Central, and North Central provinces and ≥55 mm rainfall is predicted for the rest of the country during 14th – 20th December.

Monitored Rainfall: During the last week, average daily rainfall over Sri Lanka was 5.8 mm & hydro catchment areas received 3.0 mm on average. Due to the intense impact of cyclonic storm ‘Mandous’, highest average rainfall (10.2mm) was received to the Northern plains of the country.

Monitored Wind: From 5th- 11th Dec, up to 10m/s of north westerly winds were experienced by the effect of cyclonic storm ‘Mandous’ at 850 mb level over the island .

Monitored Sea and Land Temperature: Sea surface temperature around Sri Lanka was above normal to the western, eastern, and southern half of the country. Land surface temperature remained near normal.

Interpretation

Monitoring

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

Daily Average Rainfall in the Met stations for previous week of (6th December – 13th December) =5.8 mm
Rainfall maximum : 145.1 mm & Rainfall minimum: 0.0 mm.

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

Cyclone:  The cyclonic storm ‘Mandous’ originated as a low pressure area over the southwest Bay of Bengal (8.2° N 88.2° E) and intensified into the cyclonic storm (CS) on 7th December. Then it moved west-northwestwards and developed as a severe cyclonic storm (SCS) on 8th December, maintaining 85 – 95 kmph peak wind speed for north Tamilnadu and Puducherry coasts. After making landfall on 10th December, it weakened into a deep depression (DD) over North Tamil Nadu and adjoining South Karnataka and North Kerala.

Prediction

Rainfall: During the next week (14th Dec – 20th Dec), fairly heavy (≥ 75 mm) rainfall is predicted for the Eastern, Western, Sabaragamuwa, Uva, Central, and North Central provinces; and ≥ 55 mm 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 15th – 21st December.

Teleconnections: La Niña is favored to continue into the winter, with equal chances of La Niña and ENSO-neutral during January-March 2023.
MJO shall near neutral the rainfall during 14th – 18th December, slightly increase the rainfall during 19th – 23rd December, and moderately increase the rainfall during 24th –28th 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