Weekly Hydro-meteorological Report, 8 May, 2013

Highlights

Monitoring and Prediction
Existing rainfall shall continue till 9th and South-western regions of Sri Lanka shall receive more rainfall in the coming week (7th-13th May, 2013) Entire country shall receive peak rainfall around 9th May, compared to rainfall observed on previous week.

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Summary

Monitoring


Weekly Monitoring:Rainfall ranged between 5-145 mm during 29th April-5th May 2013. Maximum rainfall was observed on the 5th May in Gampaha district. During this period, more or less the entire country experienced rainfall and heavy rainfall concentrated to South-western regions of the Island.

Predictions

7-day prediction:Entire country shall expect more than 55 mm of rainfall and South-western regions shall receive significantly heavy rainfall (more than 135 mm) during 7th-13th May 2013.

IMD WRF Model Forecast & IRI forecast:For 9th of May 2013, IMD WRF model predicts less than 8 mm of rainfall for Trincomalee district shall spreads in reducing manner toward nearby districts. For the same day rest of the island shall receive less than 1 mm of rainfall. Then for the 10th of May, IMD WRF model predicts less than 1 mm of rainfall for the island. However, for 9th & 10th IMD WRF model is unable to predict rainfall for the Southern half of the island. NOAA model predicts no significant heavy rainfall for the entire country during 7th-13th May.

1 Month Prediction:Overall Existing rainfall condition (9-12 mm/day) shall continue till 11th of May. There shall be significant rainfall event around 9th of May. Thereafter rainfall shall gradually decrease. Western Slopes – The rainfall pattern existing in the entire country shall be present in this region. Peak in rainfall is expected around 9th May (more than 20 mm/day) and thereafter rainfall shall decrease, but amount of rainfall shall be high compared to other regions. Western Coast – The rainfall pattern existing in the entire country shall be present in this region. Eastern slopes – The rainfall pattern existing in the entire country shall be present in this region. But the amount of rainfall is low compared to other regions and rainfall shall increase after 12th May. Eastern Coast – Existing rainfall shall continue and there shall be significant rainfall event around 16th. Northern region- The rainfall pattern existing in the entire country shall be present in this region. Southern Region- The rainfall pattern existing in the entire country shall be present in this region, with low amount of rainfall.

Seasonal Prediction:As per IRI Multi Model Probability Forecast issued on April 2013; for May 2013 to July 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.