Weekly Hydro-meteorological Report, 26, January 2017

Highlights:

•  The WRF model predicts up to 124 mm of rainfall in eastern coastal regions of Sri Lanka on the 27th and 28th.  
•  Between 17-23 Jan: highest rainfalls of 50 mm were recorded in Polonnaruwa district on the 20th and in Vakarai region on the 22nd.
•  From 15-21 Jan: minimum temperature of 15 ^OC was recorded from Nuwara Eliya district while many parts of the island recorded a maximum temperature between 30-35 ^OC.
•  From 17-23 Jan: up to 36 km/h north easterly winds were experienced by the northern and central regions of the island while southern regions received up to 24 km/h wind in same direction.

Download Full Report




Summary

Monitoring

Weekly Monitoring: No rainfalls were recorded within the island during the period January 17th - 19th.

Total Rainfall for past week : The RFE 2.0 tool shows total rainfall up to 75 mm for Anuradhapura, Trincomalee, Polonnaruwa, Ampara and Badulla districts; up to 50 mm of rainfall Jaffna, Mullaitivu, Mannar, Kurunegala, Kegalla, Ratnapura, Hambantota, Monaragala, Nuwara Eliya, Kandy and Matale districts; and up to 25 mm in rest of the island. It shows above average rainfall 50-100 mm for Anuradhapura, Ampara and Polonnaruwa districts; and 25-50 mm for Trincomalee, Batticaloa, Badulla, Monaragala, Matale, Kurunegala and Ratnapura districts.

Monthly Monitoring: During December – below average rainfall conditions were experienced by the entire island. Eastern regions of the island received up to 240 mm below average rainfall; and up to 150 mm in rest of the country. Monthly average rainfall for Colombo, Kalutara, Galle and Ratnapura amounted to 360 mm/month; and 180 mm/month for many parts of the island. The CPC Unified Precipitation Analysis tool shows ~200 mm of total rainfall in the coastal regions of Colombo district; ~100 mm in Kalutara, Galle, Ratnapura, Kegalla, Kandy, Matale, Ampara, Badulla and Monaragala districts; and ~50 mm in rest of the island.

Predictions

14-day prediction:
NOAA NCEP Models:
From 25th – 31st Jan: Total rainfall between 85-95 mm in Gampaha, Kegalle Colombo, Puttalam, and Kurunegala districts; 75-85 mm in Anuradhapura, Polonnaruwa, Ampara, Batticaloa, Ratnapura, Matale, Kandy, Nuwara Eliya and Badulla districts; 65-75 mm in Mannar, Vavuniya, Trincomalee, Monaragala, and Galle districts; and up to 45-55 mm in Hambantota district.
From 31st Jan – 6th Feb: No rainfall.

IMD WRF Model Forecast & IRI forecast:
 27th Jan: Rainfall more than 124 mm in Hambantota district; up to 124 mm in Ampara district; up to 64 mm in Trincomalee, Batticaloa, Polonnaruwa, Ratnapura, Badulla and Monaragala districts; and up to 35 mm of rainfall in many parts of the island.
 28th Jan: Rainfall more than 124 mm in Batticaloa and Polonnaruwa districts; up to 124 mm in Anuradhapura, Ampara and Trincomalee districts; up to 64 mm in Matale, Ratnapura and Monaragala districts; and up to 35 mm of rainfall in many parts of the island.

Seasonal Prediction: IRI Multi Model Probability Forecast February to April: the total 3-month precipitation shall be climatological for the whole island. The 3-month temperature has more than 70-80% likelihood in the entire country of being in the above-normal tercile.

Ocean State (Text Courtesy IRI)
PACIFIC SEAS STATE : January 19, 2017
During mid-January 2016 the tropical Pacific SST anomaly was near -0.5C, the threshold for weak La Niña. Many of the atmospheric variables across the tropical Pacific also remain consistent with weak La Niña conditions, although some have become only weakly so. The upper and lower atmospheric winds have continued to be weakly suggestive of a strengthened Walker circulation, and the cloudiness and rainfall remain suggestive of La Niña conditions. The collection of ENSO prediction models indicates SSTs, now near the threshold of La Niña, is in the process of dissipating to neutral levels by February.

INDIAN OCEAN STATE : Average sea surface temperature was observed in the seas around Sri Lanka.

MJO STATE : MJO shall enhance the rainfall in Sri Lanka.