Climate Bulletin For Sri Lanka (13 October 2023)

      

Highlights          

 • Heavy rainfall (≥ 105 mm) is predicted for the Southern, Sabaragamuwa, Western, Uva, Central, Eastern, North Western, North Central provinces during 12 - 18 Oct. Fairly heavy rainfall (75 mm) is predicted for the Northern province during 12 - 18 Oct.

 • During the last week, average daily rainfall over Sri Lanka was 14.5 mm and hydro catchment area received 22.3 mm. Extreme rainfall was recorded in southern coast while flash floods were experienced in Akurana on 8 Oct .

 • From 3 - 9 Oct, up to 10 m/s of west-southwesterly winds were at 850 mb (1.5 km). During 13 - 19 Oct, up to 4 m/s of north westerly winds are expected at 850 mb (1.5 km). 

 • Sea surface temperature around Sri Lanka was 0.25 - 1.0ºC above normal. From 4 - 11 Oct, maximum daily temperature was recorded in Polonnaruwa  (36.8ºC) and Vavuniya (36.2ºC).

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Predictions

Rainfall

14-day prediction: 
NOAA NCEP models: 

From 12^th October - 18^th October:

Total rainfall by Provinces

• > 135 mm - Southern, Sabaragamuwa, Western, Uva, Central
•   135 mm - Eastern, North Western
•   105 mm - North Central
•    75 mm - Northern

From 19^th October - 25^th October:

Total rainfall by Provinces

• > 135 mm - Southern, Sabaragamuwa, Western, Uva, Central, Eastern
•   135 mm - North Western
•   105 mm - North Central
•    85 mm - Northern

MJO based OLR predictions:

For the next 15 days: 

MJO shall slightly enhance the rainfall during 12^th - 16^th October, moderately enhance the rainfall during 17^th - 21^st October, and significantly enhance the rainfall during 22^nd - 26^th October for Sri Lanka.

Ocean State (Text Courtesy IRI)

Pacific Sea Sate: October 9, 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-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 19^th - 25^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: Galle, Nuwara Eliya

Daily Average Rainfall in the Met stations for previous week of (4^th October - 11^th October) = 14.5 mm

Maximum Daily Rainfall: 92.1 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	6.7	32.8	25.3
Eastern hills	22.8	27.3	18.9
Eastern plains	13.6	32.9	24.4
Western hills	21.8	27.3	19.8
Western plains	20.7	30.4	24.7
Southern plains	6.5	30.5	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	22.3	105.0	0.0

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

Temperatures: The temperature anomalies were below normal for some parts of the Western province of the country driven by the warm SST’s.

Predictions

Rainfall: During the next week (12^th October - 18^th October), heavy rainfall (≥ 105 mm) is predicted for the Southern, Sabaragamuwa, Western, Uva, Central, Eastern, North Western, and North Central provinces and fairly heavy rainfall (75 mm) is predicted for the Northern province of the country.

Temperatures: The temperature will remain seasonably near normal during 13^th - 19^th October.

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

MJO shall slightly enhance the rainfall during 12^th - 16^th October, moderately enhance the rainfall during 17^th - 21^st October, and significantly enhance the rainfall during 22^nd - 26^th October.

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