Weekly Hydro-meteorological Report, 29 January, 2015

Highlights

Monitoring and Prediction

During the past week there was limited rainfall. Rainfall is forecasted upto toals of 50 mm for the week between 28th January to 3rd February – but the predictions are at a lower value than provided with two weeks lead in the last issue. Some rainfall can be further expected during 4th to 10th February. The February to April season has a high chances of being warmer than usual.
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Summary

Monitoring


Weekly Monitoring:More or less no rainfall was observed during 21 st to 22 nd January. Rainfall was observed in western and south-west regions on 23 rd and 24 th January with highest rainfall in Kalutara,Panadura and Galle areas averaging upto 30 mm. On 25 th Mahiyangana, Budulla and Moneragala areas received rainfall averging upto 10 mm. Thereafter rainfall gradually decreased and completely ceased by 27 th January.


Monthly Monitoring:During December an average rainfall of 8 mm to 20 mm was observed throughout the country with high precipitation in the central, north-eastern and eastern regions. Highest rainfall in December was observed in Batticaloa district. Decadal rainfall average was significantly decreased during 1 st to 10 th January compared with last week of December. It further decreased during 11 th to 20 th January 2015.

Predictions

14-day prediction:NOAA NCEP models predict that heavy showers can be expected in eastern coast of the island exceeding 125 mm while rest of the country shall receive rainfall exceeding 85 mm during 28 th January to 3 rd February. Rainfall can be further expected in northern and eastern regions during 4 th February to 10 th February.

IMD WRF Model Forecast & IRI forecast:According to the IMD WRF model, rainfall can be observed throughout the country on 30 th January with high precipitation around 35 mm in northern, eastern, western regions and around 65 mm in Ratnapura. Rainfall is expected to decrease on 31 st January with highest rainfall around 35mm in Galle and Ratnapura only. IRI model predicts that rainfall can be expected in southern,western,eastern and central regions of the island during 28 th January to 2 nd February.

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

PACIFIC SEAS STATE January 15, 2014 :During December 2014 through early January 2015 the SST exceeded thresholds for weak Niño conditions, although only some of the atmospheric variables indicate an El Niño pattern. Most of the ENSO prediction models indicate weak El Niño conditions during the December-February season in progress, continuing through most or all of northern spring 2015.
INDIAN OCEAN STATE :Neutral SST was observed in the sea around Sri Lanka.
MJO STATE :MJO is weak therefore it shall not affect the rainfall in Sri Lanka.