Climate Bulletin For Sri Lanka (1 December 2023)

             

Highlights          

 • High probability of extreme rainfall is predicted during next week. Heavy rainfall (≥ 100 mm) is predicted for Central, Uva, Sabaragamuwa, Southern provinces and fairly heavy rainfall is predicted for Northern, Western provinces during  30 Nov - 6 Dec.

 • During the last week, average daily rainfall over Sri Lanka was 10.3 mm and hydro catchment was 6.6 mm. Extreme rainfall (> 150 mm/day) was in Nuwara Eliya and Galle. The rainfall of last week was twice as normal.

 • From 20 - 26 Nov, up to 5 m/s of north easterly winds were at 850 mb (1.5 km). During 30 Nov - 6 Dec, up to 8 m/s of north westerly winds are expected at 850 mb (1.5 km). 

 • Sea surface temperature around Sri Lanka was 0.25 - 1.5ºC above normal. From 23 - 29 Nov, maximum daily temperature was recorded in Ratnapura  (34.3ºC) and Puttalam (33.7ºC).

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Predictions

Rainfall

7-day prediction: 
NOAA NCEP models: 

From 30^th November - 6^th December:  

Total rainfall by Provinces

• > 130 mm - Central
• 70 - 130 mm - Sabaragamuwa, Uva, Southern
• 40 - 70 mm - Northern, Western
• 20 - 40 mm - Eastern, North Central
• ≤ 20 mm - North Western

MJO based OLR predictions:

For the next 15 days: 

MJO shall moderately enhance the rainfall during 29^th November - 3^rd December and slightly enhance the rainfall during 4^th - 13^th December for Sri Lanka.

Ocean State (Text Courtesy IRI)

Pacific Sea Sate: November 27, 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 - November. El Niño is anticipated to continue through the Northern Hemisphere spring (with a 62% chance during April -June 2024).

Indian Sea Sate

Sea surface temperature around Sri Lanka was 0.5℃ above normal to the country in 7^th - 13^th November, 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: Nuwara Eliya, Galle

Daily Average Rainfall in the Met stations for previous week of (22^nd November - 29^th November) = 10.3 mm

Maximum Daily Rainfall: 95.1 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	7.6	31.5	24.7
Eastern hills	6.3	25.5	18.4
Eastern plains	10.8	31.1	24.3
Western hills	10.5	27.9	19.4
Western plains	16.6	31.7	24.3
Southern plains	12.0	31.6	24.2

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	6.6	46.5	0.0

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

Temperatures: The temperature anomalies were above normal for some parts of the Sabaragamuwa, Central, Uva, Eastern, North Western, Western, and Southern provinces of the country driven by the warm SST’s.

Predictions

Rainfall: During the next week (30^th November - 6^th December), heavy rainfall is predicted for the Central, Sabaragamuwa, Uva, and Southern provinces and fairly heavy rainfall is predicted for the Northern and Western provinces, and less rainfall is predicted for rest of the country.

Temperatures: The temperature will remain seasonably near normal for the country during 30^th November - 6^th December.

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

MJO shall moderately enhance the rainfall during 29^th November - 3^rd December and slightly enhance the rainfall during 4^th - 13^th December for Sri Lanka.

Seasonal Precipitation: The precipitation forecast for the December-January-February, 2024 season shows near normal precipitation.