Climate Bulletin For Sri Lanka (16 December 2022)

         

Highlights          

 • 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.

 • 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 (10.2 mm) was received to the Northern plains of the country .

 • 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. During 15th - 21st Dec, up to 8m/s of north easterly winds are expected to the country.

 • 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. 

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Predictions

Rainfall

14-day prediction: 
NOAA NCEP models: 

From 14^th December – 20^th December:

Total rainfall by Provinces:   

• 85 mm - Eastern
• 75 mm - Western, Sabaragamuwa, Uva, Central, North Central
• 65 mm - Northern
• 55 mm - North Western, Southern

From 21^st December – 27^th December:

Total rainfall by Provinces:   

• 65 mm - Western
• 55 mm - Sabaragamuwa, Eastern
• 45 mm - Northern, Uva, Central, North Central
• ≤ 35 mm - Southern, North Western

MJO based OLR predictions:

For the next 15 days: 

MJO shall near neutral the rainfall during 14^th – 18^th December, slightly increase the rainfall during 19^th – 23^rd December, and moderately increase the rainfall during 24^th – 28^th December for Sri Lanka.

Ocean State (Text Courtesy IRI)

Pacific Sea Sate: December 12, 2022 

Equatorial sea surface temperatures (SSTs) are below average across most of the Pacific Ocean mid - December. The tropical Pacific atmosphere is consistent with La Niña. A large majority of the models indicate La Niña is favored to continue into the winter, with equal chances of La Niña and ENSO-neutral during January-March 2023. In February-April 2023, there is a 71% chance of ENSO-neutral.

Indian Sea Sate

Sea surface temperature around Sri Lanka was above 0.5℃ to the western, eastern, and southern half of the country in 30^th November, 2022. Across the Indian Ocean, a classical negative Indian Ocean Dipole prevails as is typical during a La Niña.

 

Interpretation

Monitoring

Rainfall: 

During the last two weeks, there had been very heavy rainfall over the following area: Jaffna

Daily Average Rainfall in the Met stations for previous week of (6^th December – 13^th December) = 5.8 mm

Rmax: 145.1 mm & Rmin: 0.0 mm.

Region	Average rainfall for the Last 8 days
Northern Plains	10.2 mm
Eastern	5.0 mm
Western	4.3 mm
Southern Plains	1.6 mm

The Hydro Catchment Areas recorded 3.0 mm of average rainfall for the last week

Rmax: 36.0 mm & Rmin: 0.0 mm.

Wind:

North westerly winds prevailed in the sea area and around the island last week.

Temperature: 

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 7^th December. Then it moved west-northwestwards and developed as a severe cyclonic storm (SCS) on 8^th December, maintaining 85 - 95 kmph peak wind speed for north Tamilnadu and Puducherry coasts. After making landfall on 10^th December, it weakened into a deep depression (DD) over North Tamil Nadu and adjoining South Karnataka and North Kerala.

Predictions

Rainfall:

During the next week (14^th Dec – 20^th 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.

Temperature:

The temperature will remain below normal for some parts of the Central, and Uva provinces during 15^th – 21^st 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 14^th – 18^th December, slightly increase the rainfall during 19^th – 23^rd December, and moderately increase the rainfall during 24^th – 28^th 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.