Weekly Hydro-meteorological Report, 21, December 2017

Highlights:

•   The WRF rainfall forecast predicts up to 36 mm of rainfall in Ampara district on December 22nd.
•   Between 12 - 18 Dec: Rainfall up to 80 mm was recorded in Badulla and Monaragala districts on December 13th.
•   From 10- 16 Dec:  minimum temperature of 15 ^OC was recorded from Nuwara Eliya district while most parts of the island recorded a maximum temperature between 30-35 ^OC.
•   From 12- 18 Dec: up to 36 km/h, northeasterly winds were experienced by the central and southern regions of the island and up to 18 km/h in northern regions.
•   0.5 ^OC above average sea surface temperature was observed in the seas around Sri Lanka.

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Summary

Monitoring

Weekly Monitoring: On December 12th, Kegalla and eastern regions of Kurunegala districts received up to 60 mm of rainfall; Kandy, Vavuniya and Anuradhapura districts up to 50 mm; northern regions of Puttalam district up to 30 mm; and several regions of Mullaitivu, Polonnaruwa, Matale and Monaragala districts up to 20 mm. On the 13th Badulla and Monaragala districts received up to 80 mm of rainfall; Kalutara, Galle, Ratnapura, Puttalam, Kurunegala and Anuradhapura districts up to 60 mm; Gampaha and Hambantota districts up to 50 mm; Polonnaruwa, Trincomalee, Ampara and Nuwara Eliya districts up to 30 mm; and Colombo, Kegalla, Kandy, Matara and Batticaloa districts up to 20 mm. On the 14th, Colombo district received up to 60 mm of rainfall; Gampaha and Kalutara districts up to 50 mm; Puttalam, Kurunegala, Kegalla, Ratnapura and Galle districts up to 30 mm; and Anuradhapura, Kandy, Nuwara Eliya, Matara and Hambantota districts up to 20 mm. On the 15th, Badulla district received up to 50 mm of rainfall; Kandy, Nuwara Eliya, Monaragala, Ampara and Hambantota districts up to 30 mm; and Gampaha, Colombo, Kalutara, Kegalla and Matale districts up to 20 mm. No significant rainfalls were recorded in any part of the island during 16th-18th.

Total Rainfall for past week :  The RFE 2.0 tool shows total rainfall of 75-100 mm in Trincomalee, Anuradhapura, Kurunegala, Gampaha, Kalutara, Galle, Badulla, Monaragala and Hambantota districts; up to 50-75 mm in Puttalam, Colombo, Ratnapura, Matale, Kandy, Nuwara Eliya and Ampara districts; up to 25-50 mm Jaffna, Mannar, Polonnaruwa and Matara districts. It shows above average rainfall up to 50-100 mm in Badulla and Monaragala districts; and up to 25-50 mm in Gampaha, Kalutara, Galle and Hambantota districts. It also shows below average rainfall up to 50-100 mm in Trincomalee, Polonnaruwa, Batticaloa and Ampara  districts; and up to 25-50 mm in Jaffna, Mannar, Mullaitivu, Matale, Kandy, Matara, Ratnapura, central regions of Anuradhapura, and western regions of Kurunegala districts.

Monthly Monitoring: During November - below average rainfall conditions were experienced in the western and central regions of the island and above average rainfall in northern, southern and eastern regions. Kurunegala, Puttalam, Anuradhapura, Polonnaruwa, Matale, and Vavuniya districts received up to 180 mm below average rainfall. Galle, Matara, Ratnapura, Hambantota, Badulla, Monaragala and Ampara districts received up to 180 mm of above average rainfall. The CPC Unified Precipitation Analysis tool shows ~500 mm of total rainfall in Colombo, Ratnapura, Galle, Matara, Hambantota, Badulla, Monaragala and Ampara districts; up to ~300 mm in Jaffna, Trincomalee, Matale, Kandy, Nuwara Eliya, Kegalla and Polonnaruwa districts.

Predictions

14-day prediction:
NOAA NCEP Models:

From 20th– 26th Dec: Total rainfall more than 135 mm in Monaragala, Ampara and Hambantota districts; between 115-125 mm in Batticaloa, Badulla and Matara districts; between 105-115 mm in Galle, Ratnapura and Nuwara Eliya districts; between 95-105 mm in Batticaloa, Polonnaruwa, Kandy and Kegalla districts; between 65-75 mm in Polonnaruwa, Matale and Gampaha districts; and up to 45-55 mm in Trincomalee, Anuradhapura, Kurunegala and Puttalam districts.

From 27th Dec- 2nd Jan : Total rainfall between 115-125 mm in Ampara district; between 95-105 mm in Batticaloa, Monaragala and Hambantota districts; between 85-95 mm in Badulla district; between 75-85 mm in Matara and Ratnapura districts; between 65-75 mm in Nuwara Eliya district; and up to 45-55 mm in Trincomalee, Polonnaruwa, Matale, Kandy and Kegalla districts.

IMD WRF Model Forecast: 

22nd Dec: Up to 36 mm of rainfall in Ampara districts; and up to 8 mm in Jaffna. Mannar, Vavuniya, Kilinochchi,  Mullaitivu, Anuradhapura, Trincomalee, Polonnaruwa, Batticaloa, Badulla, Monaragala and Hambantota districts.

23rd Dec: Up to 36 mm of rainfall in Ampara and Batticaloa districts; and up to 8 mm in Kilinochchi, Vavuniya, Anuradhapura, Polonnaruwa, Trincomalee, Badulla, Monaragala and Hambantota districts.

IRI Weekly forecast:
20th – 25th Dec: Total rainfall between 100-150 mm in Batticaloa and Ampara districts; between 75-100 mm in Trincomalee, Badulla, Monaragala and Hambantota districts districts; between 50-75 mm in Puttalam, Kurunegala, Kegalle, Kandy, Nuwara Eliya, Polonnaruwa, Ratnapura, Galle, Matara, Kalutara, Colombo and Gampaha districts; and up to 50 mm total rainfall for the rest of the island.


Ocean State (Text Courtesy IRI)
PACIFIC SEAS STATE : December 19, 2017

In mid-December 2017, the tropical Pacific reflected La Niña conditions, with SSTs in the east-central tropical Pacific in the range of weak to moderate La Niña and all atmosphere variables showing patterns suggestive of La Niña conditions. The collection of latest ENSO prediction models indicates weak, but not far from threshold of moderate, La Niña as the most likely scenario for the Northern Hemisphere winter, lasting into spring. The official CPC/IRI outlook favors continuation of La Niña through middle or late spring.

INDIAN OCEAN STATE :   0.5 ^OC above average sea surface temperature was observed in the seas around Sri Lanka.

MJO STATE :  MJO shall suppress the rainfall in Sri Lanka in the next 10 days and shall enhance the rainfall in following 5 days.