Climate Bulletin For Sri Lanka (27 October 2023)

        

Highlights          

 • Heavy rainfall (≥ 105 mm) is predicted for the Southern, Sabaragamuwa, Western, Uva, Central, North Western provinces  during 26 Oct - 1 Nov. Heavy rainfall (≥ 125 mm) is predicted for the country during 2 - 8 Nov.

 • During the last week, average daily rainfall over Sri Lanka was 13.5 mm and hydro catchment was 15.7 mm. Heavy rainfall (> 100 mm) is predicted for Southern and Western regions during next week and following week. 

 • From 17 - 23 Oct, up to 3 m/s of north westerly winds were at 850 mb (1.5 km). During 27 Oct - 2 Nov, up to 5 m/s of easterly winds are expected at 850 mb (1.5 km). 

 • Sea surface temperature around Sri Lanka was 0.25 - 1.0ºC above normal. From 18 - 25 Oct, maximum daily temperature was recorded in Vavuniya  (34.5ºC), Polonnaruwa  (33.1ºC), and Anuradhapura (33.1ºC).

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Predictions

Rainfall

14-day prediction: 
NOAA NCEP models: 

From 26^th October - 1^st November:

Total rainfall by Provinces

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

From 2^nd November - 8^th November:

Total rainfall by Provinces

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

MJO based OLR predictions:

For the next 15 days: 

MJO shall slightly suppress the rainfall during 26^th - 30^th October, slightly enhance the rainfall during 31^st October - 4^th November, and moderately enhance the rainfall during 5^th - 9^th November for Sri Lanka.

Ocean State (Text Courtesy IRI)

Pacific Sea Sate: October 23, 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 late-October. El Niño conditions are anticipated to continue through the Northern Hemisphere spring (with an 80% chance during March-May 2024).

Indian Sea Sate

Sea surface temperature around Sri Lanka was 0.5 ℃ above normal to the Southern half of the country in 3^rd - 9^th October, 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: Anuradhapura, Hambantota
Daily Average Rainfall in the Met stations for previous week of (18^th October - 25^th October) = 13.5 mm
Maximum Daily Rainfall: 161.5 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	7.3	31.6	24.3
Eastern hills	13.8	25.3	18.1
Eastern plains	9.7	31.4	23.8
Western hills	13.7	27.0	19.1
Western plains	24.1	30.3	24.2
Southern plains	18.7	30.3	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	15.7	78.0	0.0

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

Temperatures: The temperature anomalies were seasonably near normal for the country driven by the warm SST’s.

Predictions

Rainfall: During the next week (26^th October - 1^st November), heavy rainfall (≥ 105 mm) is predicted for the Southern, Sabaragamuwa, Western, Uva, Central, and North Western provinces and fairly heavy rainfall (≥ 85 mm) is predicted for the Eastern, Northern, and North Central provinces.

Temperatures: The temperature will remain seasonably near normal for the country during 27^th October - 2^nd November.

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

MJO shall slightly suppress the rainfall during 26^th - 30^th October, slightly enhance the rainfall during 31^st October - 4^th November, and moderately enhance the rainfall during 5^th - 9^th November for Sri Lanka.

Seasonal Precipitation: The precipitation forecast for the November-December-January, 2024 season shows a 40 - 45% tendency toward above normal precipitation.