Climate Bulletin For Sri Lanka (6 September 2024)

    

Highlights   

       

 •   During 4 Sep - 10 Sep, high likelihood of Light to Moderate rainfall (12.5 - 15 mm/week) is predicted for the North Western province and Light Showers (≤12.5 mm/week) is predicted for the Northern, Eastern, North Central, Southern, Sabaragamuwa, Western, Central, and Uva provinces of SL.

 •    On average, 4.8 mm/day was received in SL and rainfall was concentrated in the Western plains (10.8 mm/day) and hills (8.8 mm/day) for last 8 days. On average, 12.2 mm/day was received in the hydro catchments in SL; Kukule Ganga received the highest daily rainfall (70 mm/day) for last 8 days. Highest daily rainfall was in Galle on 30 Aug (56 mm/day).

 •   From 27 Aug - 4 Sep, winds at 850mb (1.5km) were north west - westerly, reaching up to 15 m/s. From 5 Sep - 11 Sep, winds are predicted to be north west - westerly, reaching up to 15 m/s. 

 •    Average land surface temperature was 31.5°C in the last week with warmer anomalies from seasonal average of 1-3 °C. Eastern plains was warmest followed by Northern, Southern and Western plains. Sea surface temperature around SL was 0.5°C above average for the Southern side of the country and 1.5°C above average for the other half of the country from 13 - 19 Aug.

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Monitoring

Rainfall: During the last two weeks, there has been heavy rainfall over the following area: Vogan Estate (Kalutara)

Average Rainfall in the Met stations for the previous week of (29 Aug – 4 Sep)

 = 4.8 mm/day

Maximum Daily Rainfall: 56.0 mm & Minimum Daily Rainfall: 0.0 mm.

Region	Average rainfall for 29 Aug – 4 Sep (mm/day)	Average temperature for 29 Aug – 4 Sep (ºC)
		Maximum	Minimum
Northern plains	1.0	32.9	26.5
Eastern hills	0.7	28.2	19.8
Eastern plains	0.8	34.3	25.8
Western hills	8.8	26.3	20.3
Western plain	10.8	30.8	25.6
Southern plains	7.2	31.8	25.0

Region	Average rainfall for 29 Aug – 4 Sep (mm/day)	Daily maximum rainfall for 29 Aug – 4 Sep (mm)	Daily minimum rainfall for 29 Aug – 4 Sep (mm)
All SL	4.8	56.0	0.0
Hydro catchment	12.2	70.0	0.0

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

Temperatures: The temperature anomalies were above normal for some parts of the Southern, Western and Sabaragamuwa province for Sri Lanka driven by the warm SST anomalies.

Predictions

Rainfall

14-day prediction: 
NOAA NCEP models: 

From 4^th September - 10^th September:  
Total rainfall by Provinces

• 15 mm - North Western
• ≤5 mm - Northern, Eastern, North Central, Southern, Sabaragamuwa, Western, Central, Uva

From 11^th September - 17^th September:  

Total rainfall by Provinces

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

MJO based OLR predictions:

For the next 15 days: 

MJO shall near neutral the rainfall during 3^rd September – 7^th September and slightly suppress the rainfall during 8^th–17^th September for Sri Lanka.

Ocean State (Text Courtesy IRI)

Pacific Sea Sate: September 3, 2024 

ENSO-neutral conditions are present. Equatorial sea surface temperatures (SSTs) are above average in the western Pacific and near-to-below-average in the eastern Pacific Ocean. ENSO-neutral is expected to continue for the next several months, with La Niña favored to emerge during September-November (66% chance) and persist through the Northern Hemisphere winter 2024-25 (74% chance during November-January).

Indian Sea Sate

Sea surface temperature around Sri Lanka was 0.5°C above average for the Southern side of the country and 1.5°C above average for the other half of the country from 13 Aug to 19 Aug 2024.

Interpretation

Monitoring

Rainfall: For August 2024, we had double than the average rainfall. This rise was driven by random and heavy cloud cover over the northern hemisphere due to the tropical convergence zone’s latitude of around 10-15֯ N. The Indian Oceanic Dome developed, leading to decreased temperature around SL and possible rainfall to the East of SL. 

Wind: The wind was flowing North West - West and was quite high.

              

Predictions

Rainfall: During the next week (4 Sep - 10 Sep ), Light to Moderate rainfall (12.5 - 15 mm) is predicted for the North Western province and Light Showers (12.5 mm) is predicted for the Northern, Eastern, North Central, Southern, Sabaragamuwa, Western, Central, and Uva provinces.

Temperatures: The temperature will remain above normal for the Northern, Eastern, Southern and Uva provinces during 5 - 11 September.

Teleconnections: MJO shall near neutral the rainfall during 3^rd September – 7^th September and slightly suppress the rainfall during 8^th–17^th September for Sri Lanka.

Seasonal Precipitation: The precipitation forecast for the September-October-November, 2024 season shows a 45% or more tendency toward above normal precipitation for the Eastern part of the  country.