Climate Bulletin For Sri Lanka (3 May 2024)

Highlights          

 • High likelihood of light to moderate rainfall (15 - 25 mm) is predicted for the Western, Sabaragamuwa North Western, Southern, Central Provinces and light shower (≤ 5 mm) is predicted for the rest during 1 - 7 May.

 • On average, only 2/3 of expected rainfall was received over the Sri Lanka during   April. Average rainfall for SL was 4.1mm and for the hydro-catchment areas was 4.7mm.

 • Winds at 850mb (1.5 km) were easterly from 22 - 28 Apr reaching up to 4 m/s. Winds at 850mb (1.5 km) are predicted south westerly from 2 - 8 May reaching up to 5 m/s. Winds are low speed and transitioning in direction. 

 • Average land surface temperature was 33.8ºC in the last week and warmer anomalies of +1-3ºC were higher in the western slopes, coast and southern region compared to the northern and eastern  regions. Sea surface temperature around Sri Lanka was 0.5 - 1.5ºC above normal.

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Predictions

Rainfall

14-day prediction: 
NOAA NCEP models: 

From 1^st May - 7^th May: 

Total rainfall by Provinces

• 25 mm - Western, Sabaragamuwa
• 15 mm - North Western,  Southern,  Central
• ≤ 5 mm - Northern, Eastern, Uva, North Central

From 8^th May - 14^th May: 

Total rainfall by Provinces

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

MJO based OLR predictions:

For the next 15 days: 

MJO shall moderately enhance the rainfall during 1^st - 10^th May, and near neutral the rainfall during 11^th - 15^th May for Sri Lanka.        

Ocean State (Text Courtesy IRI)

Pacific Sea Sate: April 29, 2024 

The SST Anomalies for the NINO3.4 region show a +1.2 ºC on the week ending 29^th April, and a weak El Nino is sustained. Consensus of models predict a continuation of the El Niño event until May 2024 before weakening thereafter.

Indian Sea Sate

Sea surface temperature around Sri Lanka was 0.5℃ above normal to the Western, Southern, and Northern half of the country in 9^th- 15^th April 2024.    

Interpretation

Monitoring

Rainfall: : During the last two weeks, there had been heavy rainfall over the following areas: Gampaha, Ratnapura.

Daily Average Rainfall in the Met stations for previous week of (24^th April - 1^st May) = 4.1 mm

Maximum Daily Rainfall: 127.8 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	2.4	35.6	26.5
Eastern hills	2.7	29.3	19.4
Eastern plains	1.3	34.6	26.1
Western hills	8.7	31.4	20.9
Western plains	8.1	33.6	26.1
Southern plains	2.4	34.3	26.2

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	4.7	112.0	0.0

Wind: 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 North Western, Western, Sabaragamuwa, Southern, Central, North Central, and Uva provinces of the country, driven by the warm SST’s.                                             

Predictions

Rainfall: During the next week (1^st May - 7^th May), light to moderate rainfall (15 - 25 mm) is predicted for the Western, Sabaragamuwa North Western, Southern, and Central Provinces and light showers (≤ 5 mm) are predicted for the rest.

Temperatures: The temperature will remain above normal for some parts of the Northern, North Central, Uva, Eastern, Central, and North Western provinces during 2^nd - 8^th May.

Teleconnections: MJO shall moderately enhance the rainfall during 1^st - 10^th May, and near neutral the rainfall during 11^th - 15^th May for Sri Lanka.       

Seasonal Precipitation: The precipitation forecast for the May-June-July, 2024 season shows a 70% or more tendency toward above normal precipitation for the country.