Climate Bulletin For Sri Lanka (2 September 2022)

  

Highlights          

 • Up to 80 mm of rainfall is predicted for Central and Sabaragamuwa provinces, below 75mm of rainfall is expected for the rest of the country  during 2nd-7th September.

 • During the last week, the average daily rainfall over Sri Lanka was 5.6 mm and hydro catchment areas have received 10.13 mm on average.

 • From 22nd- 28th August, south-westerly  of 10m/s winds were experienced at 850 mb level over the island. Upto 10m/s of westerlies to south-westerly winds expected for the next week.

 •  Sea surface temperature around Sri Lanka was above 0.5℃ to the north of Sri Lanka. Land surface temperature remained near normal.

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Predictions

Rainfall

14-day prediction: 
NOAA NCEP models: 

From 31^st August – 6^th September:

Total rainfall by Provinces: 

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

From 7^th September – 13^th September:

Total rainfall by Provinces: 

•   35 mm - Central, Sabaragamuwa
•   25 mm - Western, Uva
• < 15 mm - Southern, Eastern

MJO based OLR predictions:

For the next 15 days: 

MJO shall slightly enhance the rainfall during 31^st August - 4^th September and shall near neutral during 5^th September – 14^th September.

Ocean State (Text Courtesy IRI)

Pacific Sea Sate: August 24, 2022 

Equatorial sea surface temperatures (SSTs) are below average across most of the Pacific Ocean in late-August. The tropical Pacific atmosphere is consistent with La Niña. A large majority of the models indicate, La Niña is expected to continue, with chances for La Niña gradually decreasing from 86% in the coming season to 60% during December-February 2022-23.

Indian Sea Sate

Sea surface temperature around Sri Lanka was above 0.5℃ to the north of Sri Lanka. 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 heavy rainfall over the following area: Polonnaruwa

Daily Average Rainfall in the Met stations for previous week of (22^nd Aug - 29^th Aug) = 5.6 mm

Rmax: 102.5 mm & Rmin: 0.0 mm.

Region	Average rainfall for the Last 8 days
Northern Plains	5.7 mm
Eastern	7.0 mm
Western	5.4 mm
Southern Plains	0.0 mm

The Hydro Catchment Areas recorded 10.13 mm of average rainfall for the last week

Rmax: 96.5 mm & Rmin: 0.0 mm. 

Wind:

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

Temperature: 

The temperature anomalies were below normal for the northern half of the island, driven by the warm SST’s.

Predictions

Rainfall:

During the next week (2^nd- 6^th September) up to 80 mm of rainfall is predicted for Central and Sabaragamuwa provinces, and < 75mm rainfall is expected for the rest of the country.

Temperature:

The temperature will remain slightly above normal for the Uva province during 2^nd September – 7^st September.

Teleconnections:

La Niña - La Niña is expected to continue, with chances for La Niña gradually decreasing from 86% in the coming season to 60% during December-February 2022-23.

MJO shall slightly enhance the rainfall during 31^st August - 4^th September and shall near neutral during 5^th September – 14^th September.

Seasonal Precipitation: 

The precipitation forecast for the September-October-November season shows a higher tendency for below-normal precipitation for the country.