Weekly Hydro-meteorological Report, 3 April, 2014

Highlights

Monitoring and Prediction
Very dry conditions were observed in Sri Lanka during the last month except for some slight amounts of rainfall received particularly in areas towards the western slopes of the country. However less than average rainfall was observed in all parts of the country. Base on IRI and NOAA predictions for the next two weeks, rainfall is expected to increase. MJO is in the 3rd phase which shall influence rainfall in Sri Lanka.

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Summary

Monitoring


Weekly Monitoring:During 25th- 31st of March No rainfall was observed in any part of Sri Lanka except on the 27th, where up to 20 mm of rainfall was observed in Kegalle district.


Monthly Monitoring:Region towards west to south-west of the central mountains of Sri Lanka received upto 1 mm average rainfall during the month of March 2014. But except for north and north central provinces the rest of the island received a below average rainfall.

Predictions

14-day prediction:During the next two weeks up to 90 mm of rainfall is predicted for the southern half of the island.

IMD WRF Model Forecast & IRI forecast: on the 5th of April, rainfall is expected in all of Sri Lanka except in the north. Areas around Colombo and Ratnapura shall have rainfall up to 35 mm. On the 6th Rainfall shall increase where the predicted rainfall around Colombo is up to 65 mm. and the Western slopes will also have rainfall up to 35 mm. No rainfall is observed in Northern areas of the country on this day as well. The IRI model predicts upto 200 mm of rainfall for the southern half of the country and this rainfall shall diminish towards northern parts of the country.

1 Month Prediction:Overall-During 30 day period starting from 2nd of April 2014, rainfall is expected to be constant around 3 mm per day. Western Slopes- Up to 10 mm of rainfall is expected around 8th of April and it shall decrease afterwards. Western Coast- Almost constant amount around 5 mm of rainfall is expected in this region. Eastern Slopes- A fluctuating pattern of rainfall shall be observed around 2 mm. Eastern Coast- Very less amount (below 4 mm) of rainfall is expected in this region Northern- Rainfall is expected to reach aorund 4 mm on 3th of April and shall decrease gradually thereafter. Southern Region- Existing rainfall shall decrease until 13th of April and thereafter no rainfall is expected until around 27th.

Seasonal Prediction:As per IRI Multi Model Probability Forecast issued on March 2014; for April 2014 to June 2014, there is a 40-45% probability for temperature to be above normal in the country while the rainfall is to be climatological.

PACIFIC SEAS STATE March 20, 2013 :During February through mid-March the observed ENSO conditions varied from cool-neutral to the borderline of weak La Niña. However, many of the ENSO prediction models indicate a warming trend, with neutral ENSO during northern spring 2014 and a fairly likely development of weak El Niño conditions by the end of northern summer.

INDIAN OCEAN STATE :The seas around Sri Lanka showed neutral sea surface temperature during 23rd-29th March 2014.
MJO STATE :MJO is in phase 3 (in the Indian Ocean) and shall influence the rainfall in Sri Lanka.