Weekly Hydro-meteorological Report, 2, May 2019

Highlights:

•   The IRI weekly rainfall forecast predicts up to 75 mm of total rainfall in Galle district during 1 – 6 May.
•   Between 23 – 29 Apr: up to 70 mm of rainfall was recorded in Ratnapura district on the 29th.
•  From 23 – 29 Apr: up to 12 km/h, northeasterly winds were experienced by the entire island.
•   1 ⁰C above average sea surface temperature was observed in the seas around Sri Lanka.

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Summary

Monitoring

Weekly Monitoring: On April 23rd, Mullaitivu, Mannar, Vavuniya, Anuradhapura and Colombo districts received up to 30 mm of rainfall; and Puttalam, Batticaloa, Kurunegala, Gampaha, Kalutara, Ratnapura, Badulla and Monaragala districts up to 20 mm. On the 24th, Puttalam, Kurunegala, Badulla and Monaragala districts received up to 5 mm of rainfall. On the 25th, Kurunegala and Gampaha districts received up to 60 mm of rainfall; Gampaha, Kalutara, Ratnapura and Kegalle districts up to 50 mm; Puttalam, Anuradhapura, Kandy, Nuwara Eliya, Galle, Hambantota and Monaragala districts up to 30 mm; and Vavuniya, Polonnaruwa, Matale, Badulla and Ampara districts up to 20 mm; and rest of the country up to 10 mm. On the 26th, Jaffna and Kilinochchi districts received up to 5 mm of rainfall. On the 27th, Anuradhapura and Puttalam districts received up to 20 mm of rainfall. On the 28th, Vavuniya and Monaragala districts received up to 30 mm of rainfall; Kilinochchi, Mullaitivu, Mannar, Anuradhapura, Polonnaruwa, Ratnapura and Badulla districts up to 20 mm; and up to 10 mm in most parts of the island. On the 29th, Ratnapura district received up to 70 mm of rainfall; Batticaloa, Ampara and Monaragala districts up to 50 mm; Badulla, Kandy, Kalutara and Galle districts up to 30 mm; and Kurunegala, Gampaha, Kegalle, Kandy, Polonnaruwa, Colombo and Hambantota districts up to 20 mm.

Total Rainfall for past week :  The RFE 2.0 tool shows total up to 75-100 mm in Kurunegala, Gampaha, Kegalle and Ratnapura districts; up to 50-75 mm in Colombo, Kalutara and Galle districts; and 25-50 mm in Vavuniya, Anuradhapura, Puttalam, Matale, Kandy, Nuwara Eliya, Matara, Hambantota, Badulla, Monaragala, Polonnaruwa, Batticaloa and Ampara districts. Above average rainfall up to 50-100 mm is shown for Ratnapura district; and up to 25-50 mm in Ampara district. Below average rainfall up to 25-50 mm is shown for Anuradhapura, Puttalam, Kurunegala, Matale, Kandy, Nuwara Eliya and Badulla districts; and up to 10-25 mm in Jaffna, Kilinochchi, Mannar, Mullaitivu, Vavuniya, Trincomalee, Polonnaruwa, Monaragala, Kalutara and Matara 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 1st – 7th May: Total rainfall up to 55 mm Galle and Matara districts; up to 35-45 mm in Gampaha, Colombo and Ratnapura districts; up to 25-35 mm in Kegalle, Nuwara Eliya, Badulla, Monaragala and Hambantota districts; and up to 15-25 mm in Puttalam, Kurunegala, Anuradhapura, Matale, Kandy and Ampara districts.

From 8th – 14th May: Total rainfall up to 35 mm in Gampaha and Colombo districts; and up to 15-25 mm Puttalam, Kurunegala, Anuradhapura, Matale, Kegalle and Ratnapura districts

IMD WRF Model Forecast: 

3rd May: Up to 160 mm of rainfall in Ratnapura, Badulla and Monaragala districts; and up to 80 mm in Gampaha, Kegalle and Hambantota districts; up to 40 mm in Colombo, Kalutara and Nuwara Eliya districts; and up to 20 mm in Puttalam, Kurunegala, Kandy, Batticaloa, Ampara, Galle and Matara districts.

4th May: Up to 160 mm of rainfall in Batticaloa, Colombo, Kegalle, Matara and Ratnapura districts; and up to 80 mm in Gampaha, Kalutara, Nuwara Eliya and Hambantota districts.

IRI Weekly forecast:
From 1st – 6th May: Total rainfall up to 75 mm is expected in Galle district; and up to 50 mm Colombo, Kalutara, Kegalle, Kandy, Nuwara Eliya, Badulla and Ratnapura 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 :   1 ⁰C above average sea surface temperature was observed in the seas around Sri Lanka.

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