Climate Bulletin For Sri Lanka (15 October 2021)

Highlights          

                   

 • Fairly heavy rainfall is predicted for Central, Southern, Western and Sabaragamuwa provinces during 15th - 19th Oct. Greater likelihood of dry tendency is predicted for southern Sri Lanka from Oct to Dec.

 • Very heavy rainfall was observed in the Northern and North Western provinces with max of 200.3 mm in Jaffna district on 10th Oct according to ground observations.

 •   From 5th Oct - 12th Oct, up to 40 km/h Southwesterlies were experienced across the island

 •   Sea surface temperature was observed above 0.5℃ all around Sri Lanka.

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Predictions

Rainfall

14-day prediction: 
NOAA NCEP models: 

From 13^th – 19^th  October: 

Total rainfall by Provinces

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

From 20^th – 26^th  October: 

Total rainfall by Provinces:

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

MJO based OLR predictions:

For the next 15 days: 

MJO shall be active, thus giving slightly suppressed rainfall during 13^{th –} 27^th October. 

Ocean State (Text Courtesy IRI)

Pacific Sea Sate: October 6, 2021 

Equatorial SSTs were near-to-below average across most of the equatorial Pacific Ocean, and were above average in the western Pacific Ocean in the early-October. A large majority of the model forecasts predict a transition from ENSO-neutral to La Niña is favored in the next couple of months and La Niña to continue through the Northern Hemisphere fall and winter.

Indian Sea Sate

Sea surface temperature was observed above 0.5℃ all around Sri Lanka. 

Interpretation

Monitoring

Rainfall: 

During the last two weeks, there had been very heavy rainfall over the Northern and North-Western provinces and heavy rainfall over the Central, Southern and Western provinces. 

Wind: 

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

Temperature: 

The temperature anomalies were below normal by 1⁰C – 3⁰C in the North Central province while near-neutral for the rest of the country last week, driven by the warm SST’s.

Predictions

Rainfall:

During the next week (15^th - 19^th October) fairly heavy rainfall is predicted for Central, Sabaragamuwa, Southern and Western provinces. 

Temperature:

The temperature remains slightly normal for October. During 15^th – 23^rd October, the temperature remains high especially in the Eastern, North Central and Uva provinces.

Teleconnections:

La Nina -The SST forecast indicates that ENSO-neutral are present and a transition from ENSO-neutral to La Niña is favored in the next couple of months.

MJO shall be active, thus giving slightly suppressed rainfall during 13^{th –} 27^th October. 

Seasonal Precipitation: 

October to December is the main rainfall season in Sri Lanka. The consensus predictions has switched from neutral to favoring a dry tendency.  A dry tendency can hurt agricultural production and it adds to farmer difficulties due to the fertilizer bans. However, since this is the wet season the impact will not be as severe. 

However, the bigger impact shall be that it shall reduce the generated hydropower in the coming months. This can hurt the economy due to the scarcity in Foreign Exchange within the country due to the Central Bank regulations.