Weekly Hydro-meteorological Report, 28 March 2013

Highlights

Monitoring and Prediction
Heavy rainfall was observed throughout the country in spells of 2 to 3 days in the past week. No extreme rainfall events were observed in the past week nor predicted for the next couple of weeks. The Sea Surface Temperature around Sri Lanka continues to have a positive anomaly.

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Summary

Monitoring


Weekly Monitoring:During 20th – 27th March period south western regions of the country received rainfall up to 30 mm while the rest of the country was dry. On the 23rd, the eastern side of the country received rainfall up to 30 mm while the North West and the West of the island received very less amounts of rainfall. On the next day rainfall shifted towards north western regions of the country while heavy rainfall was observed in the sea further west of Kalmunai area. Rainfall dwindled in the next two days with rainfall up to 30 mm was observed in western and south western regions on the 25th and south eastern region on the 26th.

Predictions

7-day prediction:During 27th March- 1st April up to 25 mm rainfall is predicted in south western and north eastern regions of the country.

IMD WRF Model Forecast & IRI forecast:The whole country save for the coastal areas in the east of the country shall receive rainfall up to 35 mm on the 29th of March with the exception of regions around Ratnapura which shall receive rainfall up to 65 mm. Rainfall shall diminish on the next day. The whole country except for the Northern, North Western, and Western are expected to have rainfall up to 35 mm. NOAA model predicts rainfall up to 50 mm during the period 27th March- 1st April 2013.

1 Month Prediction: Overall- No unusually high rainfall events are predicted within the 30 day period starting from 26th March 2013. Western Slopes – Maximum rainfall is prediccted around 27th March and it shall decrease gradually until the 15 April. Thereafter an increasing trend in the rainfall is expected. Western Coast –Rainfall shall more or less be constant throughout the 30 day period with fluctuations. Eastern slopes –Rainfall shall decrease until 10th of April and shall once again increase after 13th. Eastern Coast –Very less amount of rainfall is expected until 20th of April and no rainfall is expected thereafter. Northern region- Rainfall shall fluctuate around 2 mm. Southern Region- Very less amount of rainfall expected.

Seasonal Prediction:As per IRI Multi Model Probability Forecast issued on March 2013; for April 2013 to June 2013, there is a 50- 60% probability for temperature to be above normal in the country while the rainfall is to be climatological.

PACIFIC SEAS STATE February 21, 2013 :During January through mid-March the observed ENSO conditions have leaned towards La-Nina, but remained in the neutral range. 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 and possible weak El Nino.

INDIAN OCEAN STATE :The Indian Ocean around Sri Lanka particular to the South continues to have a warm anomaly while SST increases further to the South.