Weekly Hydro-meteorological Report, 18 April, 2013

Highlights

Monitoring and Prediction
Western half of the island shall receive rainfall during 17th-23rd April. For the coming two days rainfall shall be concentrated in the Kalutara, Ratnapura, Kegalle district, some places in Polonnaruwa district (on 19th) and Nuwara Eliya district (on 20th). For the entire country existing rainfall conditions shall decrease gradually till 21st and increase thereafter.

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Summary

Monitoring


Weekly Monitoring:Rainfall ranged between 5-95 mm during 8th-15th March 2013. Maximum rainfall was observed on the 13th April in Kandy district. During 13th-15th almost entirety of the country received rainfall.

Predictions

7-day prediction:Western half of the island shall receive 5-55 mm of rainfall during 17th-23rd April.

IMD WRF Model Forecast & IRI forecast:For 19th of April 2013, IMD WRF model predicts 8-36 mm of rainfall for Kalutara, Ratnapura, Kegalle districts and some places in Polonnaruwa district and, spreads towards nearby regions in a reducing manner. In the same day, for the Hambantota, Ampara, Batticaloa districts and northern half of the island, less than 1 mm of rainfall is predicted. Then for the 20th of April, IMD WRF model predicts more rainfall in the Nuwara Eliya district and the rest of the island shall receive less than 1 mm of rainfall. NOAA model predicts wet weather conditions for Matara, Galle and Kalutara districts during 17th-22nd April.

1 Month Prediction:Overall- Existing rainfall condition shall decrease gradually till 21st and increase thereafter. Western Slopes – The rainfall pattern existing in the island shall be present in this region. Western Coast – There shall be rainfall peaks around 19th & 26th. Eastern slopes - Existing rainfall condition shall persist in the range of 1-5 mm with variations till 26th April. Eastern Coast – Rainfall is not predicted till 25th. Northern region- Rainfall shall increase gradually, but significant rainfall peaks are not predicted during the month of April. Southern Region- No significant amount of rainfall is predicted till 22nd.

Seasonal Prediction:As per IRI Multi Model Probability Forecast issued on March 2013; for April 2013 to June 2013, there is a 45-50% probability for temperature to be above normal in the country while the rainfall is to be climatological.

PACIFIC SEAS STATE April 18, 2013 :During February through March the observed ENSO conditions remained in the neutral ENSO conditions. Most of the ENSO prediction models call for neutral ENSO conditions through northern summer 2013, but some statistical models call for weak La-Nina while some dynamical models call for warming & possible weak El-Nino.

INDIAN OCEAN STATE :The Indian Ocean around Sri Lanka particular to the Bay of Bengal continues to have a warm anomaly up to 0.5˚C. Warm SST conditions are spreading towards seas north of Sri Lanka.