Climate Bulletin For Sri Lanka (17 September 2021)

 

Highlights          

                   

•  Heavy rainfall is predicted for Sabaragamuwa, Southern and Western provinces during 17th - 21st Sept. Greater likelihood of dry tendency than normal is predicted in the southern SL from October to December.

 •  Fairly heavy rains were experienced in the Western,  Sabaragamuwa, Southern & North Western provinces with max of 91.7 mm in Ratnapura district on 15th September.

 •  From 7th - 13th September: up to  15 km/h from Southwesterly were experienced over the island.

 •  Sea surface temperature was observed above 0.5℃ to the South and West of Sri Lanka and neutral to the rest.

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Predictions

Rainfall

14-day prediction: 
NOAA NCEP models: 

From 15^th – 21^st September: 

Total rainfall by Provinces

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

From 22^nd – 28^th September: 

Total rainfall by Provinces:

• 105 mm - Sabaragamuwa
•  95 mm - Southern, Western
•  85 mm - Central
•  65 mm - North Western, Uva
•  45 mm - Eastern, North Central
•  35 mm - Northern

MJO based OLR predictions:

For the next 15 days: 

MJO shall be active, thus giving slightly enhanced rainfall during 17^th – 29^th September. 

Ocean State (Text Courtesy IRI)

Pacific Sea Sate: September 8, 2021 

Equatorial SSTs were below average in parts of the eastern Pacific Ocean and near average across the rest of the Pacific Ocean in early-September and most key atmospheric variables were ENSO –Neutral condition. A large majority of the model forecasts predict ENSO-neutral likely to continue through the Northern Hemisphere summer.

Indian Sea Sate

Sea surface temperature was observed above 0.5℃ to the South and West of Sri Lanka and neutral to the rest.

Interpretation

Monitoring

Rainfall: 

During the last two weeks, there had been fairly heavy rainfall over the following Provinces: Sabaragamuwa, Western, North-Western and Southern.

Wind: 

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

Temperature: 

The temperature anomalies were near-neutral for the whole country last week – driven by the warm SST’s.

Predictions

Rainfall:

During the next week (17^th – 21^st September) heavy rainfall is predicted for Sabaragamuwa, Southern and Western provinces. 

Temperature:

The temperature remains slightly normal for September. During 17^th – 25^th September, the temperature remains high especially in the Eastern, Northern, North Central and Uva provinces.

Teleconnections:

La Nina -The SST forecast indicates that the La Niña event has transitioned to ENSO-neutral and will likely remain so through the boreal summer. 

MJO shall be active, thus giving slightly enhanced rainfall during 17^th – 29^th September. 

Seasonal Precipitation: 

October to December is the main rainfall season in Sri Lanka. The consensus has switched from neutral to having a dry tendency.  If so, it can hurt agriculture adding to fertilizer bans and hydro-power generation, given $ scarcity.