Weekly Hydro-meteorological Report, 25, April 2019

Highlights:

•   The IRI weekly rainfall forecast predicts up to 300 mm of total rainfall in Mullaitivu and Trincomalee districts during 24 – 29 Apr.
•   Between 16 – 22 Apr: up to 140 mm of rainfall was recorded in Anuradhapura district on the 20th.
•  From 16 – 22 Apr: up to 10 km/h, easterly winds were experienced by the entire island.
•   0.5 ⁰C above average sea surface temperature was observed in the seas around Sri Lanka.

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Summary

Monitoring

Weekly Monitoring: On April 16th, Colombo district received up to 30 mm of rainfall; and Jaffna, Kurunegala, Gampaha, Kegalle, Kandy, Kalutara, Galle and Ratnapura districts up to 20 mm. On the 17th, Gampaha district received up to 100 mm of rainfall; Kurunegala district up to 90 mm; Puttalam and Kegalle districts up to 80 mm; Badulla district up to 60 mm; Colombo, Kalutara, Ratnapura, Nuwara Eliya and Monaragala districts up to 50 mm; Kandy, Ampara, Galle, Matara and Hambantota districts up to 30 mm; and Anuradhapura, Polonnaruwa and Matale districts up to 20 mm. On the 18th, Kurunegala, Gampaha, Kegalle, Kalutara and Galle districts received up to 10 mm of rainfall. On the 19th, Anuradhapura, Mannar, Vavuniya, Jaffna, Kilinochchi, Gampaha and Kegalle districts received up to 20 mm of rainfall. On the 20th, Anuradhapura district received up to 140 mm of rainfall; Kurunegala district up to 80 mm; Matale district up to 60 mm; Puttalam, Gampaha and Polonnaruwa districts up to 50 mm; Mannar, Vavuniya, Mullaitivu and Trincomalee districts up to 30 mm; and Jaffna, Kilinochchi, Batticaloa, Badulla, Kandy, Kegalle, Colombo and Kalutara districts up to 20 mm. On the 21st, Kurunegala district received up to 50 mm of rainfall; Anuradhapura, Matale, Kegalle and Gampaha districts up to 30 mm; and Polonnaruwa, Ampara, Kandy and Puttalam districts up to 20 mm. On the 22nd, Puttalam, Kurunegala, Kandy and Nuwara Eliya districts received up to 5 mm of rainfall.

Total Rainfall for past week :  The RFE 2.0 tool shows total up to 150-200 mm in Kurunegala and Gampaha districts; up to 100-150 mm in Puttalam and Kegalle districts; up to 75-100 mm in Anuradhapura, Colombo, Kalutara, Ratnapura and Matale districts; up to 50-75 mm in Mannar, Kandy, Nuwara Eliya, Badulla and Monaragala districts; and 25-50 mm in rest of the island. Above average rainfall up to 50-100 mm is shown for Gampaha, Puttalam, Kurunegala and Anuradhapura districts; up to 25-50 mm in Badulla and Matale districts; and up to 10-25 mm Mannar, Vavuniya, Colombo and Nuwara Eliya districts. Below average rainfall up to 25-50 mm is shown for Matara district; and up to 10-25 mm in Galle, Hambantota, Monaragala, Kandy, Ratnapura, Batticaloa and Trincomalee districts.

Monthly Monitoring: During March – Above average rainfall conditions up to 60 mm were experienced in coastal regions of Galle and Matara districts. Below average rainfall conditions up to 180 mm were experienced by Anuradhapura, Polonnaruwa, Batticaloa, Ampara, Monaragala, Ratnapura, Nuwara Eliya, Badulla, Kandy, Kegalle, Matale, Kurunegala and Puttalam districts; and up to 60 mm in rest of the island. The CPC Unified Precipitation Analysis tool shows up to 100 mm of total rainfall in Gampaha, Ratnapura and Kalutara districts; up to 75 mm in Kegalle, Colombo, Galle and Nuwara Eliya districts; up to 50 mm in Puttalam, Kurunegala Kandy, Matara, Monaragala and Badulla districts; and up to 25 mm in Mannar, Anuradhapura, Matale, Batticaloa, Ampara and Hambantota districts. 

Predictions

14-day prediction:
NOAA NCEP Models:

From 24th – 30th Apr: Total rainfall more than 135 mm in Jaffna, Kilinochchi, Mannar, Mullaitivu, Vavuniya, Anuradhapura, Polonnaruwa, Trincomalee, Batticaloa, Matale, Nuwara Eliya, Kurunegala, Puttalam, Badulla, Monaragala and Ampara districts; up to 125-135 mm in Gampaha, Kegalle and Ratnapura districts; up to 115-125 mm in Colombo, Kalutara and Hambantota districts; and up to 95-105 mm in Galle and Matara districts.

From 1st – 7th May: Total rainfall up to 55 mm in Gampaha, Colombo, Ratnapura, Galle and Matara districts; up to 35-45 mm Nuwara Eliya,, Badulla, Monaragala, Ratnapura, Puttalam, Kurunegala and Hambantota districts; up to 25-35 mm in Kandy, Matale and Ampara districts; and up to 15-55 mm in rest of the island.

IMD WRF Model Forecast: 

26th Apr: Up to 160 mm of rainfall in Matale, Kandy, Kurunegala, Kegalle, Ratnapura, Badulla and Monaragala districts; and up to 80 mm in Anuradhapura, Kandy and Matara districts.

27th Apr: Up to 160 mm of rainfall in Galle and Matara districts; and up to 80 mm in Ratnapura district.

IRI Weekly forecast:
From 24th – 29th Apr: Total rainfall up to 300 mm is expected in Mullaitivu and Trincomalee districts; up to 200 mm in Jaffna, Kilinochchi, Vavuniya, Anuradhapura, Polonnaruwa, Batticaloa and Ampara districts; up to 150 mm Mannar, Puttalam, Kurunegala, Matale, Kandy, Badulla and Monaragala districts; up to 100 mm in Gampaha, Colombo, kalutara, Kegalle, Ratnapura, Nuwara Eliya and Hambantota districts; and up to 75 mm Galle and Matara districts.

Ocean State (Text Courtesy IRI)
PACIFIC SEAS STATE : April 19, 2018

SSTs in the tropical Pacific maintained a weak El Niño level during March and early April, while temperature anomalies of subsurface waters decreased somewhat but continued to be positive. Patterns in the atmosphere show weak El Niño conditions. Collective model forecasts show a continuation of at least weak El Niño-level SSTs lasting through 2019. The somewhat more cautious official CPC/IRI outlook, with an El Niño advisory, calls for an approximate 65% chance of El Niño prevailing during Jun-Aug, decreasing to 50-55% for Sep-Nov.

INDIAN OCEAN STATE :   0.5 ⁰C above average sea surface temperature was observed in the seas around Sri Lanka.

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