Weekly Hydro-meteorological Report, 04 June, 2015

Highlights:


During 27th May – 2nd June 2015, high rainfall was observed towards the end of the week which was an increase when compared to the previous week. In the beginning of the week there were no rain in any part of the country and the Eastern and Uva provinces observed rainfall up to 70 mm/day from 30th May. Highest rainfall of 70 mm was observed in Ampara. Central, Sabaragamuwa, North Eastern and North Western provinces also received rainfall up to 10-30 mm/day. NOAA models predict high rainfall in Eastern, South Eastern and Western provinces in the next fortnight.
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Summary

Monitoring


Weekly Monitoring::During the time period 27th May – 2nd June 2015, only Sabaragamuwa, Uva and Eastern provinces received rainfall. In the first 3 days there was no any significant rainfall observed in the whole country. On the 30th of May up to 30 mm light rainfall in central to eastern regions of the country. Then up to 90 mm very heavy rainfall was observed in the Ampara district on the 31st of May while up to 30 mm rainfall was observed in Sabaragamuwa. Rainfall decreased on the 1st of June where only Ampara and Batticaloa districts received up to 30 mm rainfall. On the 2nd Mahiyangana and Badulla districts received up to 30 mm rainfall.


Monthly Monitoring:In May 2015 Most of the country received above average rainfall. Gampaha, Colombo, Kaluthara and Galle districts as well as western regions of Kegalle and Ratnapura districts received below average rainfall. Highest monthly average rainfall in this month was observed in Anuradhapura and Vavunia districts and northern regions of Badulla and Ampara districts.

Predictions

14-day prediction: NOAA NCEP models predict high rainfall in northern regions of Sri Lanka during 3rd – 16th June 2015. Up to 55 mm total rainfall is expected during 3rd – 9th June and the rainfall shall further increase up to about 85 mm (total) in the following week.

IMD WRF Model Forecast & IRI forecast: According to the IMD WRF model, the entire country except for northern, north-central and Hambantota regions shall receive up to 35 mm rainfall on the 5th of June. This may go up to about 65 mm in Mahiyangana area. Rainfall shall decrease on the 6th where only light rainfall is expected in south eastern regions. IRI CFS model also predict high rainfall in Mahiyangana area during 1st- 6th June. However no unusually heavy rainfall is expected in any part of the country during these six days.

Seasonal Prediction:As per IRI Multi Model Probability Forecast for June to August, the total 3 month precipitation shall be climatological. The 3 month temperature has more than 70-80% likelihood in the entire country of being in the above-normal tercile during this period.

PACIFIC SEAS STATE May 21, 2014 :During late April through mid-May 2015 the SST was at a weak to moderate Niño level. The atmospheric variables also indicate an El Niño pattern, including weakened trade winds, low Southern Oscillation Index and excess rainfall in the central tropical Pacific. The consensus of ENSO prediction models indicate weak to moderate El Niño conditions during the May-July 2015 season in progress, likely strengthening during summer and lasting through 2015.
INDIAN OCEAN STATE :0.5 degrees C above average temperature was observed in the southern sea of Sri Lanka. The anomaly goes further up towards south-west.
MJO STATE :MJO is in phase 1 and therefore shall slightly enhance the rainfall in Sri Lanka.