Climate Bulletin For Sri Lanka (22 September 2023)

   

Highlights          

 • Heavy rainfall (≥ 115 mm) is predicted for the Sabaragamuwa, Southern, Western provinces and fairly heavy rainfall (≥ 65 mm) is predicted for the Uva, Central, North Western provinces during 21 - 27 Sep.

 • During the last week, average daily rainfall over Sri Lanka was 21.1 mm and  hydro catchment areas received 6.7 mm. Highest average rainfall of 17.9 mm/day received Western plains.

 • From 12 - 18 Sep, up to 15 m/s of west-southwesterly winds were at 850 mb (1.5 km). During 22 - 28 Sep, up to 10 m/s of northwest-southwesterly winds are expected at 850 mb (1.5 km). 

 • Sea surface temperature around Sri Lanka was 0.25 - 1.5ºC above normal. From 13 - 20 Sep, maximum daily temperature was recorded in Polonnaruwa (38.3ºC) and Mullaitivu (37.0ºC).

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Predictions

Rainfall

14-day prediction: 
NOAA NCEP models: 

From 21^st September - 27^th September:  

Total rainfall by Provinces

• 125 mm - Southern, Sabaragamuwa
• 115 mm - Western
•  85 mm - Uva, Central
•  65 mm - North Western
•  45 mm - Eastern
•  25 mm - North Central
• ≤ 15 mm - Northern

From 28^th September - 4^th October:    

Total rainfall by Provinces

•  ≥ 135 mm - Southern, Sabaragamuwa, Western
•     105 mm - Uva, Central
•      85 mm - North Western
•      65 mm - Eastern
•      25 mm - North Central
•  ≤ 15 mm - Northern

MJO based OLR predictions:

For the next 15 days: 

MJO shall near neutral the rainfall during 21^st September - 5^th October for Sri Lanka.

Ocean State (Text Courtesy IRI)

Pacific Sea Sate: September 18, 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 mid-September. El Niño conditions will continue through the Northern Hemisphere winter (with greater than a 95% chance through January - March 2024).

Indian Sea Sate

Sea surface temperature around Sri Lanka was 0.5 ℃ above normal to the Western, Southern, and Northern half of the country in 29^th August - 4^th September, 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 very heavy rainfall over the following area: Galle

Daily Average Rainfall in the Met stations for previous week of (13^th September - 20^th September) = 21.1 mm

Maximum Daily Rainfall: 95.0 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	2.4	32.9	25.6
Eastern hills	10.4	27.6	19.1
Eastern plains	3.6	34.0	24.9
Western hills	8.4	27.5	19.3
Western plains	17.9	30.4	24.9
Southern plains	14.2	30.2	24.3

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	6.7	53.0	0.0

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

Temperatures: The temperature anomalies were above normal for some parts of the Northern and Uva provinces of the country driven by the warm SST’s.

Predictions

Rainfall: During the next week (21^st September - 27^th September), heavy rainfall (≥ 115 mm) is predicted for the Southern, Sabaragamuwa, and Western provinces and fairly heavy rainfall (≥ 65 mm) is predicted for the Uva, Central, and North Western 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 22^nd September - 28^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 21^st September - 5^th October for Sri Lanka.

Seasonal Precipitation: The precipitation forecast for the October-November-December, 2023 season shows a 50 - 60% tendency toward above normal precipitation for the country.