Climate Bulletin For Sri Lanka (8 September 2023)

 

Highlights          

 • Fairly heavy rainfall (≥ 65 mm) is predicted for the Sabaragamuwa, Southern, Western, Uva, Central provinces and less rainfall is predicted for the rest of the country during 7 - 13 Sep.

 • During the last week, average daily rainfall over Sri Lanka was 7.1 mm and  hydro catchment areas received 16.3 mm. Highest average rainfall of 23.7 mm/day received Western plains.

 • From 29 Aug- 4 Sep, up to 15 m/s of north westerly winds were at 850 mb (1.5 km). During 8 - 14 Sep, up to 15 m/s of northwest-southwesterly winds are expected at 850 mb (1.5 km). 

 • Sea surface temperature around Sri Lanka was 0.5 - 1.5ºC above normal. From 30 Aug - 6 Sep, maximum daily temperature was recorded in Trincomalee (37.7ºC) and Polonnaruwa (36.6ºC).

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Predictions

Rainfall

14-day prediction: 
NOAA NCEP models: 

From 7^th September – 13^th September:  

Total rainfall by Provinces

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

From 14^th September – 20^th September:   

Total rainfall by Provinces

• 75 mm - Southern, Sabaragamuwa
• 65 mm - Western
• 55 mm - Uva, Central
• 35 mm - Eastern
• 25 mm - North Western
• ≤ 15mm - Northern, North Central

MJO based OLR predictions:

For the next 15 days: 

MJO shall slightly enhance the rainfall during 7^th - 16^th September and near neutral the rainfall during 17^th - 21^st September for Sri Lanka.

Ocean State (Text Courtesy IRI)

Pacific Sea Sate: September 5, 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 early-September. El Niño conditions will 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 0.5 ℃ above normal to the country in 15^th - 21^st 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 areas:

Galle, Kalutara, Colombo, Ratnapura

Daily Average Rainfall in the Met stations for previous week of (30^th August - 6^th September) = 7.1 mm
Maximum Daily Rainfall: 85.1 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	2.5	33.3	26.1
Eastern hills	6.1	26.5	19.3
Eastern plains	3.2	34.0	25.5
Western hills	22.1	25.3	19.9
Western plains	23.7	29.9	24.5
Southern plains	15.1	30.4	24.4

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	16.3	115.0	0.0

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

Temperatures: The temperature anomalies were near normal for the country driven by the warm SST’s.

Predictions

Rainfall: During the next week (7^th September - 13^th September), fairly heavy rainfall (≥ 65 mm) is predicted for the Southern, Sabaragamuwa, Western, Uva, and 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, Northern, North Central, and Uva provinces and below normal for some parts of the Central province during 8^th September - 14^th September.

Teleconnections: A positive Dipole Mode has set in across the Indian Ocean since 8^th of June.

MJO shall slightly enhance the rainfall during 7^th - 16^th September and near neutral the rainfall during 17^th - 21^st September for Sri Lanka.

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