Climate Bulletin For Sri Lanka (13 September 2024)

     

Highlights   

       

 •   During 11 Sep - 17 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, 2.7 mm/day was received in SL and rainfall was concentrated in the Western plains (7.9 mm/day) and hills (6 mm/day) for last 8 days. On average, 7.2 mm/day was received in the hydro catchments in SL; Kukule Ganga received the highest daily rainfall (42 mm/day) for last 8 days. Highest daily rainfall was in Ratnapura on 9 Sep (44.2 mm/day).

 •   From 3 Sep - 9 Sep, winds at 850mb (1.5km) were north westerly, reaching up to 15 m/s. From 12 Sep - 18 Sep, winds are predicted to be north westerly, reaching up to 15 m/s.  

 •    Average land surface temperature was 31.5ºC in the last week with warmer anomalies from seasonal average of 1-3 ºC. Eastern plains was warmest followed by Northern, Southern and Western plains. Sea surface temperature around Sri Lanka was 0.5°C above average for the Western side of the country and 1°C above average for the other half of the country from 20 -26 Aug 2024.

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Monitoring

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

Average Rainfall in the Met stations for the previous week of (5–11 Sep) = 2.7 mm/day

Maximum Daily Rainfall: 44.2 mm & Minimum Daily Rainfall: 0.0 mm.

Region	Average rainfall for 5 – 11 Sep (mm/day)	Average temperature for 5 – 11 Sep (ºC)
		Maximum	Minimum
Northern plains	0.1	33.2	26.7
Eastern hills	0.0	29.6	19.4
Eastern plains	0.2	35.7	26.0
Western hills	6.0	26.5	20.3
Western plain	7.9	31.1	25.8
Southern plains	1.2	32.4	25.4

Region	Average rainfall for 5 – 11 Sep (mm/day)	Daily maximum rainfall for 5 – 11 Sep (mm)	Daily minimum rainfall for 5 – 11 Sep (mm)
All SL	2.7	44.2	0.0
Hydro catchment	7.2	42.0	0.0

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

Temperatures: The temperature anomalies were above normal for some parts of the Uva province for Sri Lanka driven by the warm SST anomalies.

Predictions

Rainfall

14-day prediction: 
NOAA NCEP models: 

From 11^th September - 17^th September:  
Total rainfall by Provinces

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

From 18^th September - 24^th September:    

Total rainfall by Provinces

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

MJO based OLR predictions:

For the next 15 days: 

MJO shall near neutral the rainfall during 12-26 September for Sri Lanka.

Ocean State (Text Courtesy IRI)

Pacific Sea Sate: September 9, 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 Western side of the country and 1°C above average for the other half of the country from 20-26 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 Westerly and was quite high.

              

Predictions

Rainfall: During the next week (11 Sep - 17 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, North Central and Uva provinces during 13 - 19 September.
Teleconnections: MJO shall near neutral the rainfall during 12-26 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.