Climate Bulletin For Sri Lanka (6 October 2023)

     

Highlights          

 • Heavy rainfall (≥ 115 mm) is predicted for the Southern, Sabaragamuwa, Western, Uva, Central and Eastern provinces during 5 - 11 Oct. Fairly heavy rainfall (≥ 65 mm) is predicted for the North Western and North Central provinces during 5 - 11 Oct.

 • During the last week, average daily rainfall over Sri Lanka was 17.0 mm and hydro catchment area received 18.0 mm. Extreme rainfall was recorded in southern coast.

 • From 26 Sep - 2 Oct, up to 15 m/s of south westerly winds were at 850 mb (1.5 km). During 6 - 12 Oct, up to 6 m/s of southwesterly winds are expected at 850 mb (1.5 km). 

 • Sea surface temperature around Sri Lanka was 0.25 - 1.0ºC above normal. From 27 Sep - 4 Oct, maximum daily temperature was recorded in Vavuniya (36.5ºC), Polonnaruwa (35.8ºC) and Mullaitivu (35.4ºC).

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Predictions

Rainfall

14-day prediction: 
NOAA NCEP models: 

From 5^th October - 11^th October:  

Total rainfall by Provinces

• ≥ 135 mm - Southern, Sabaragamuwa, Western, Uva
•   125 mm - Central
•   115 mm - Eastern
•    95 mm - North Western
•    65 mm - North Central
•  ≤ 35 mm - Northern

From 12^th October - 18^th October:

Total rainfall by Provinces

• ≥ 135 mm - Southern, Sabaragamuwa, Western, Uva
•   125 mm - Central
•   115 mm - Eastern
•   105 mm - North Western
•    75 mm - North Central
•    45 mm - Northern

MJO based OLR predictions:

For the next 15 days: 

MJO shall near neutral the rainfall during 5^th - 14^th October and slightly enhance the rainfall during 15^th - 19^th October for Sri Lanka.

Ocean State (Text Courtesy IRI)

Pacific Sea Sate: October 2, 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-October. 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 and Southern half of the country in 12^th - 18^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 areas: Hambantota, Ratnapura

Daily Average Rainfall in the Met stations for previous week of (27^th September - 4^th October) = 17.0 mm

Maximum Daily Rainfall: 226.4 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	3.5	32.2	25.4
Eastern hills	2.7	26.4	19.5
Eastern plains	6.5	33.2	25.0
Western hills	20.3	25.5	19.6
Western plains	31.2	29.7	23.9
Southern plains	46.0	28.9	23.9

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	18.0	120.0	0.0

Wind: South 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 (5^th October - 11^th October), heavy rainfall (≥ 115 mm) is predicted for the Southern, Sabaragamuwa, Western, Uva, Central, and Eastern provinces and fairly heavy rainfall (≥ 65 mm) is predicted for the 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 Northern and Eastern provinces and below normal for some parts of the Central and Uva provinces during 6^th - 12^th October.

Teleconnections: A positive Dipole Mode has set in across the Indian Ocean since 8^th of June. MJO shall near neutral the rainfall during 5^th - 14^th October and slightly enhance the rainfall during 15^th - 19^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.