Weekly Hydro-meteorological Report, 30, November 2017

Highlights:

•   The WRF rainfall forecast predicts up to 124.5 mm of rainfall in Gampaha, Colombo and Kalutara districts on December 1st.
•   Between 22-27 Nov: Rainfall up to 120 mm was recorded in Batticaloa district on November 25th.
•   From 19-25 Nov: 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 21-27 Nov: up to 36 km/h, northeasterly winds were experienced by the entire island.
•   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 November 22nd, the Batticaloa district received up to 50 mm of rainfall; Ampara and Hambantota districts up to 30 mm; Polonnaruwa, Matale, Kandy, Nuwara Eliya, Kalutara, Galle, Matara, Badulla and Monaragala districts up to 20 mm; and many southern and central regions of the island up to 10 mm. On the 23rd Galle district received up to 30 mm of rainfall; Kalutara, Ratnapura, Matara and Hambantota districts up to 20 mm. On the 24th, Jaffna, Mannar, Puttalam, Trincomalee, Polonnaruwa, Matale and Kandy districts received up to 10 mm of rainfall. On the 25th Batticaloa district received up to 120 mm of rainfall; Ampara district up to 90 mm; Polonnaruwa, Badulla and Monaragala districts up to 80 mm; Trincomalee, Anuradhapura, Kurunegala, Matale and Kandy districts up to 50 mm; Mullaitivu, Vavuniya, Puttalam and Nuwara Eliya up to 30 mm; and the rest of the island up to 20 mm. On the 26th, Trincomalee, Batticaloa and Polonnaruwa districts received up to 80 mm; Mullaitivu, Vavuniya, Mannar, Anuradhapura, Kandy, Nuwara Eliya, Badulla, Monaragala and Ampara districts received up to 50 mm; Jaffna, Kilinochchi, Puttalam, Kurunegala, Matale,  and Hambantota districts up to 30 mm; and rest of the island up to 10 mm. On the 27th, Anuradhapura district received up to 60 mm; Puttalam, Mannar,  Batticaloa, Ampara and Monaragala districts up to 50 mm; Jaffna, Vavuniya, Badulla and Polonnaruwa districts up to 30 mm; Kilinochchi, Mullaitivu, Matale, Kandy, Nuwara Eliya and Hambantota districts up to 20 mm; and rest of the island up to 10 mm.

Total Rainfall for past week :  The RFE 2.0 tool shows total rainfall of 200-300 mm in Batticaloa and Ampara districts; up to 150-200 mm in Trincomalee, Polonnaruwa and Monaragala districts; up to 75-100 mm Kilinochchi, Mullaitivu, Vavuniya, Mannar, Anuradhapura, Puttalam, Kurunegala, Kegalla, Ratnapura, Nuwara Eliya, Badulla, Monaragala, Hambantota, Ratnapura and Matara districts. It shows above average rainfall up to 100-200 mm in Polonnaruwa, Batticaloa, Ampara and Monaragala districts; and up to 50 -100 mm in Trincomalee, Kandy, Nuwara Eliya and Badulla districts. It also shows below average rainfall up to 50-100 mm in Puttalam, Gampaha, Colombo, Kalutara and Ratnapura districts; and up to 25-50 mm in Kurunegala and Galle districts.

Monthly Monitoring: During October - below average rainfall conditions were experienced in the northern, western and southern regions of the island and above average rainfall in central and eastern regions. Puttalam and Galle districts received up to 180 mm below average rainfall; Jaffna, Mullaitivu, Kilinochchi, Mannar, Gampaha, Kalutara, Ratnapura, Matara and Hambantota districts up to 120 mm. The Polonnaruwa district received up to 240 mm of above average rainfall; Batticaloa, Trincomalee, Ampara, Badulla, Monaragala and Matale districts up to 150 mm; and Kandy, Kegalle and Nuwara Eliya districts up to 120 mm. The CPC Unified Precipitation Analysis tool shows ~360 mm of total rainfall in the Polonnaruwa district; up to ~300 mm in Anuradhapura, and Batticaloa, Trincomalee, Ampara, Badulla, Kurunegala, Kegalla, Ratnapura and Matale districts.

Predictions

14-day prediction:
NOAA NCEP Models:

From 29th Nov – 05th Dec: Total rainfall between 75-85 mm in Jaffna district; between 65-75 mm in Kilinochchi and Mullaitivu districts; between 35-45 mm in Trincomalee, Ampara, Batticaloa, Monaragala and Galle districts; between 25-35 mm in Vavuniya, Mannar, Ratnapura, Matara and Badulla districts; between 15-25 mm in Anuradhapura, Polonnaruwa, Puttalam, Gampaha, Colombo, Kegalle and Nuwara Eliya districts; Up to 15 mm total rainfall for the rest of the island.

From 06th – 12th Dec : Total rainfall between 85-95 mm in Jaffna and Kilinochchi districts; between 65-75 mm in Mullaitivu and Trincomalee districts; between 55-65 mm in Mannar, Vavuniya, Anuradhapura, Polonnaruwa and Batticaloa districts; between 45-55 mm in Puttalam, Gampaha, Colombo, Kegalle, Ratnapura, Kurunegala, Matale, Badulla, Monaragala and Ampara districts; between 35-45 mm in Kandy, Nuwara Eliya and Galle districts; Up to 35 mm total rainfall for the rest of the island.

IMD WRF Model Forecast: 

01st Dec: Up to 124.5 mm of rainfall in Gampaha, Colombo and Kalutara districts; Up to 64.5 mm in Puttalam, Kurunegala, Kegalle and Ratnapura districts; Up to 35.6 mm in Anuradhapura, Polonnaruwa, Trincomalee, Matale, Nuwara Eliya, Badulla, Monaragala, Ampara, Hambantota, Matara and Galle districts. Up to 7.6 mm rainfall for the rest of the island.

02nd Dec: Up to 35.6 mm of rainfall in Jaffna, Kilinochchi, Colombo, Kalutara, Ratnapura and Galle districts; Up to 7.6 mm in Mullaitivu, Anuradhapura, Polonnaruwa, Matale, Badulla, Ampara, Monaragala, Hambantota, Matara, Nuwara Eliya, Colombo and Kegalle districts; Up to 2.5 mm rainfall for the rest of the island.

IRI Weekly forecast:
29th Nov – 04th Dec: Total rainfall between 100-150 mm in Jaffna, Kilinochchi, Mullaitivu, Trincomalee, Kalutara, Galle and Matara districts; between 75-100 mm in Mannar, Vavuniya, Anuradhapura, Gampaha, Colombo, Ratnapura, Hambantota, Monaragala and Ampara districts; between 50-75 mm in Puttalam, Kurunegala, Kegalle, Kandy, Nuwara Eliya, Badulla, Batticaloa and Polonnaruwa districts; Up to 50 mm total rainfall for the rest of the island.


Ocean State (Text Courtesy IRI)
PACIFIC SEAS STATE : November 20, 2017

In mid-November 2017, the tropical Pacific reflected weak La Niña conditions, with SSTs in the east-central tropical Pacific past the threshold of La Niña and most atmosphere variables showing patterns suggestive of weak La Niña conditions. The collection of latest ENSO prediction models indicates weak La Niña as the most likely scenario for the remainder of Northern Hemisphere fall and for the winter. The official CPC/IRI outlook favors continuation of La Niña through winter, and carries a La Niña advisory.

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

MJO STATE :  MJO shall not have a significant impact on the rainfall in Sri Lanka in the next 5 days and shall suppress the rainfall in the following 10 days.