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Wednesday, March 4, 2015

Weekly Hydro-meteorological Report, 4 March, 2015


Rainfall increased significantly during the last week with rainfall reaching magnitude of 100 mm reporting in Kurunegala and Ampara districts. The average rainfall during the February was above average in most parts of the country. Rainfall is expected to increase further during the week after 10 th of March.
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Weekly Monitoring:: During 24 th February - 2 nd March 2015 rainfall was observed throughout the country. On the 24 th Kegalle and Trincomalee districts received rainfall up to 30 mm. On the 25 th heavy rainfall was observed in Ampara district reaching up to 100 mm in magnitude. Up to 30 mm rainfall was observed on the 26 th throughout the country. Rainfall continued on the 27 th in central southern and south western parts of the country with higher magnitudes in Ratnapura and Kaluthara districts while rainfall ceased in northern, eastern and north western parts of the country. On the 28 th rainfall ceased in most parts of the country while south western parts received light rainfall. Once again heavy rainfall was observed on the 1 st of March with the magnitude in Kurunagala reaching up to 100 mm. Rainfall was only observed in Galle, Matara, Kaluthara and Colombo districts on the 2 nd .

Monthly Monitoring: After a dry January, almost the entirety of the country received above average rainfall during February. Only places where less than average rainfall was observed are Pu ttalam, Kurunegala and Polonnaruwa districts. Batticaloa and Ratnapura areas received highest rainfall during this month. An increase in rainfall was observed during 21 st – 28 th February compared to 11 th -20 th .


14-day prediction: NOAA NCEP models predict entire country shall receive rainfall during 3 rd - 9 th March up to 35 mm. These models further predict that the rainfall during 10 th - 16 th March shall increase up to 75 mm.

IMD WRF Model Forecast & IRI forecast: According to the IMD WRF model, entire country shall receive rainfall on 5 th of March with higher rainfall (up to 35 mm) in the western half of the country. Rainfall in Ratnapura area may go up to 65 mm on this day. A decrease in rainfall is predicted for the 6 th of March with light rainfall expected throughout the country. IRI models also predict higher rainfall in Nuwara Eliya and Ratnapura regions during 3 rd - 8 th of March. But extreme rainfall events are not likely during this period.

Seasonal Prediction: As per IRI Multi Model Probability Forecast for March to May, the total 3 month precipitation shall be climatological. The 3 month average temperature has more than 60- 70% likelihood of being in the above-normal tercile during this period.

PACIFIC SEAS STATE February 19, 2014 :During January through early February 2015 the SST just met the thresholds for weak Niño conditions. Lately some of the atmospheric variables began indicating an El Niño pattern a little more than they had been before January. The consensus of ENSO prediction models indicate warm neutral to borderline El Niño conditions during the February-April season in progress, continuing into northern spring 2015, with some suggestion of strengthening El Niño toward mid-2015.
INDIAN OCEAN STATE :Neutral SST was observed in the sea around Sri Lanka.
MJO STATE :MJO is weak. Therefore it shall not have a significant impact on rainfall in Sri Lanka.

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