Weekly Hydro-meteorological Report, 23 May, 2013

Highlights

Monitoring and Prediction
In the coming week, Southwestern regions shall experience significant amount of rainfall, especially in the Galle district, heavy rainfall shall be observed in the coming two days (30th and 31st May). However, in most of regions of Sri Lanka, existing rainfall shall decrease during 31st May-2nd June. Thereafter it shall gradually increase till 10th of May. However, northern &southern regions shall not experience the same phenomena as other regions.

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Summary

Monitoring


Weekly Monitoring:Rainfall ranged between 5-145 mm during 21st-27th May 2013. Maximum rainfall was concentrated on the 22nd May for a small part of Galle district. Rest of the days of the week received rainfall of 5-10 mm/day.

Predictions

7-day prediction:South-western regions shall receive 55-95 mm of rainfall & rest of the island shall receive 5-55 mm of rainfall during 28th May -3rd June 2013.

IMD WRF Model Forecast & IRI forecast:For 30th May, IMD WRF model predicts more than 125 mm of rainfall for the Southwestern coastal regions & it shall spread in a reducing manner towards Jaffna & Hambantota districts along the coastal belts. For the same day, model predicts less than 1 mm of rainfall for the eastern half of the island. For 31st May, model predicts more the 125 mm of rainfall for Galle district & rainfall shall spread as the previous day. For the same day, Batticaloa & Ampara districts shall receive less than 8 mm of rainfall. NOAA model predicts less than 50 mm of rainfall for the entire country, except for the Northern regions (less than 20 mm) during 28th May -2nd June.

1 Month Prediction:Overall- Existing rainfall shall decrease during 31st May-2nd June. Thereafter it shall gradually increase till 10th of May. Western Slopes – The rainfall pattern existing in the entire country shall be present in this region. But significant rainfall trough shall be observed around 2nd June. Western Coast – The rainfall pattern existing in the entire country shall be present in this region. Eastern Slopes – Existing rainfall condition shall persists till the end of May & rainfall shall gradually decrease till 17th June. Eastern Coast – The rainfall shall decrease drastically till 2nd June & gradually increase thereafter. Northern region- The rainfall shall increase till the end of May & shall reduce gradually till 2nd June. Thereafter once again it shall increase, but significant rainfall events shall not be expected in this period. Southern Region- The rainfall pattern existing in Northern region shall be present in this region.

Seasonal Prediction:As per IRI Multi Model Probability Forecast issued on May 2013; for June 2013 to August 2013, there is a 60-70% probability for temperature to be above normal in the country while the rainfall is to be climatological.

PACIFIC SEAS STATE May 16, 2013 :During March through May the observed ENSO conditions remained in the neutral. Most of the ENSO prediction models indicate a continuation of neutral ENSO into northern autumn. However few models, mainly but not exclusively statistical models call for cooling towards borderline or weak La-Nina conditions during the coming northern summer season into the latter part of the 2013.

INDIAN OCEAN STATE :The cold anomaly which was observed in the Indian Ocean around Sri Lanka has shifted towards a non-anomalous state.