Climate Bulletin For Sri Lanka (22 May 2024)

 

Highlights          

 • High likelihood of heavy rainfall (100 -150mm) is predicted for the Western, Sabaragamuwa, North Western, Southern provinces and fairly heavy rainfall (50 - 100mm) is predicted for the Central, North Central, and Uva provinces during 21 - 27 May. 

 • For SL, 150 mm rainfall was received during 15 - 20 May. Apart from Western region, upto 4 - 12mm deficit of rainfall was observed during April. Depression 99B in the BoB is predicted to reach cyclone status and then track away from SL. 

 • Winds at 850mb (1.5 km) were north westerly from 12  - 18 May reaching up to 3 m/s. Winds at 850mb (1.5 km) are predicted north westerly  from 22 - 28 May reaching up to 20 m/s due to depression 99B (JTWC classification).

 • Average land surface temperature was 30.3ºC in the last week with warmer anomalies of +1-3ºC. Sea surface temperature around Sri Lanka was 0.5 - 2.0ºC above normal. The temperature has dropped slightly

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Predictions

Rainfall

14-day prediction: 
NOAA NCEP models: 

From 21^st May - 27^th May:  

Total rainfall by Provinces

• 115 mm - Western
• 105 mm - North Western, Southern, Sabaragamuwa  
•  95 mm - Central
•  75 mm - North Central, Uva
•  65 mm - Northern
•  55 mm - Eastern

From 28^th May - 3^rd June:  

Total rainfall by Provinces

• 65 mm - North Western, Western
• 55 mm - Southern, Sabaragamuwa  
• 45 mm - Central
• 35 mm - North Central, Northern
• 25 mm - Uva, Eastern

MJO based OLR predictions:

For the next 15 days: 

MJO shall moderately enhance the rainfall during 21^st - 25^th May, near neutral the rainfall during 26^th - 30^th May, and moderately suppress the rainfall during 31^st May - 4^th June for Sri Lanka.   

Ocean State (Text Courtesy IRI)

Pacific Sea Sate: May 20, 2024 

El Niño is transitioning toward ENSO-neutral. Equatorial sea surface temperatures (SSTs) are above average in the western and central Pacific Ocean, and below-average SSTs are emerging in east central and eastern Pacific Ocean. La Niña may develop in June-August 2024 (49% chance) or July-September (69% chance).

Indian Sea Sate

Sea surface temperature around Sri Lanka was 1.5℃ above normal for the country in 30^th April - 6^th May 2024.

Cyclone 'Remal'

IMD predicts that the cyclonic storm in Bay of Bengal shall intensify into a cyclone by the 25^th and as typically for this season shall steer away from SL. However, if the cyclone stalls there could continue to be severe winds and heavy rainfall in the western slopes of the mountains in SL.

Interpretation

Monitoring

Rainfall: : During the last two weeks, there had been very heavy rainfall over the following area: Kesbewa. 

Daily Average Rainfall in the Met stations for previous week of (18^th May - 21^st May) = 23.1 mm

Maximum Daily Rainfall: 214.5 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	29.0	31.6	25.3
Eastern hills	2.8	27.2	20.5
Eastern plains	11.1	32.8	25.5
Western hills	19.5	26.1	20.3
Western plains	45.4	29.6	24.6
Southern plains	2.2	31.3	25.4

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	23.4	88.0	0.0

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

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

Predictions

Rainfall: During the next week (21^st May - 27^th May), heavy rainfall (100 - 150 mm) is predicted for the Western, Sabaragamuwa, North Western, and Southern provinces and fairly heavy rainfall (50 - 100 mm) is predicted for the rest.

Temperatures: The temperature will remain below normal for some parts of the Central, Western, North Western, Southern, and Northern provinces and above normal some parts of eastern province during 22^nd - 28^th May.

Teleconnections: MJO shall moderately enhance the rainfall during 21^st - 25^th May, near neutral the rainfall during 26^th - 30^th May, and moderately suppress the rainfall during 31^st May - 4^th June for Sri Lanka.

Seasonal Precipitation: The precipitation forecast for the June-July-August, 2024 season shows a 50% or more tendency toward above normal precipitation for the country.