Climate Bulletin For Sri Lanka (1 September 2023)

      

Highlights          

 • Very heavy rainfall (>135mm) is predicted for the Southern Province: heavy rainfall (>100mm) is predicted for Sabaragamuwa, Western, Uva, Central and Eastern provinces from 31 Aug - 6 Sept.

 • During the last week, average daily rainfall over Sri Lanka was 'light' (2.6 mm) and  hydro catchment areas received  'light' (4.9 mm) showers. Overall, 33% drop in rainfall during the August.

 • From 15 - 21 Aug, up to 8 m/s of southwesterly winds were at 850 mb (1.5 km). During 1 - 7 Sept, up to 15 m/s of westerly -southwesterly winds are expected at 850 mb (1.5 km). 

 • Sea surface temperature around Sri Lanka was 0.5 - 2ºC above normal. From 22 - 29 Aug, maximum daily temperature was recorded in Vavuniya (38.3ºC), and Polonnaruwa (37.7ºC)

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Predictions

Rainfall

14-day prediction: 
NOAA NCEP models: 

From 31^st August – 6^th September:  

Total rainfall by Provinces

• >135 mm - Southern
• 125 mm - Sabaragamuwa
• 115 mm - Western, Uva
• 105 mm - Central, Eastern
•  85 mm - North Western
•  55 mm - North Central
•  45 mm - Northern

From 7^th September – 13^th September:  

Total rainfall by Provinces

• 45 mm - Southern, Sabaragamuwa
• 35 mm - Western, Uva, Central, Eastern
• 25 mm - North Western 
• 15 mm - North Central, Northern

MJO based OLR predictions:

For the next 15 days: 

MJO shall near neutral the rainfall during 31^st August - 14^th September for Sri Lanka

Ocean State (Text Courtesy IRI)

Pacific Sea Sate: Aguste 8, 2023 

El Nino Mode has set in according to NOAA since 8^th of June. Equatorial sea surface temperatures (SSTs) are above average across the central and eastern Pacific Ocean. El Niño is anticipated to continue through the Northern Hemisphere winter (with greater than a 95% chance through December 2023-February 2024).             

Indian Sea Sate

Sea surface temperature around Sri Lanka was 1.0 ℃ above normal to the South and 0.5 ℃ to the West of the country in 8^th - 14^th August, 2023. A positive Dipole Mode has set in across the Indian Ocean since 8^th of June.

Interpretation

Monitoring

Rainfall:

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

Ratnapura.

Daily Average Rainfall in the Met stations for previous week of (22^th August - 29^th August) = 2.6 mm

Maximum Daily Rainfall: 101.3 mm & Minimum Daily Rainfall: 0.0 mm. 

Region	Average rainfall for last 8 days (mm)	Average temperature for last 8 days (ºC)
		Maximum	Minimum
Northern plains	0.4	34.7	26.2
Eastern hills	5.4	29.4	18.3
Eastern plains	1.4	35.4	25.4
Western hills	9.4	29.7	19.2
Western plains	3.7	32.5	25.9
Southern plains	0.0	33.6	25.7

Region	Average rainfall for last 8 days (mm)	Daily maximum rainfall for last 8 days (mm)	Daily minimum rainfall for last 8 days (mm)
Hydro catchment	4.9	63.0	0.0

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

Temperatures: The temperature anomalies were above normal for the entire island and expect provinces of the country driven by the warm SST’s.

Predictions

Rainfall: During the next week (31^st August - 6^th September), very heavy rainfall (>135mm) is predicted for the Southern Province: heavy rainfall (>100mm) is predicted for Sabaragamuwa, Western, Uva, Central and Eastern provinces; fairly heavy rainfall (55-85 mm) is for North Western and North Central provinces and less rainfall is predicted for the rest of the country.

Temperatures: The temperature will remain above normal for some parts of the Eastern, Uva, Northern, and North Central provinces and below normal for Nuwara Eliya district during 1^st September - 10^th September.

Teleconnections: A positive Dipole Mode has set in across the Indian Ocean since 8^th of June. MJO shall near neutral the rainfall during 31^st August - 14^th September for Sri Lanka

Seasonal Precipitation: The precipitation forecast for the September-October-November, 2023 season shows above normal precipitation for the country.