Weekly Hydro-meteorological Report, 21 May, 2015

Highlights:


Relatively high rainfall was observed during 12th- 18th May 2015 in Sri Lanka. Heavy rainfall was observed in Vavuniya and Puttalam districts during this period. The rest of the country received up to 30 mm rainfall as well. NOAA models predict a continuation in high rainfall during the next two weeks
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Summary

Monitoring


Weekly Monitoring::During the time period 12th May – 18th May 2015, the rainfall was observed up to 30 mm/day and it showed a decrease when compared to the previous week. The average rainfall received throughout the whole week was up to 10-30 mm/day and the northern region of the country received a rainfall of 30 mm/day. In 12th May the Northern and North Central provinces received heavy rainfall, which was the highest in the week, of 130 mm in Vavuniya. In the next few days Northern and North East provinces received rainfall up to 30 mm and since 15th May the rainfall decreased gradually up to 10 mm/day. On 16th and 17th May rainfall up to 30 mm was received into the North, North East and North West provinces while Puttalam district and the adjacent sea received up to 90 mm rainfall. On the 18th May the whole country received an average rainfall of 10 mm/day while Northern region of Ratnarura District showed a rainfall up to 30 mm.


Monthly Monitoring: In April 2015 the entire country received above average rainfall except in Trincomalee, Batticaloa, Jaffna and Polonnaruwa districts and the northern regions of Ampara district.

Predictions

14-day prediction: NOAA NCEP models predict high rainfall up to 30 mm/day in the entire the country except North Eastern region during the next fortnight.

IMD WRF Model Forecast & IRI forecast: According to the IMD WRF model, Western and Southern regions of the country shall receive rainfall up to 35 mm and the rest of the country shall not receive any rainfall on 22nd and 23rd May. NOAA CFS models don not predict a significant amount of rainfall in Sri Lanka during 20th- 25th May 2015.

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 14, 2014 :During April through early-May 2015 the SST met the threshold for weak Niño conditions. Most of the atmospheric variables now indicate an El Niño pattern, including weakened trade winds, low Southern Oscillation Index and excess rainfall in the vicinity of the dateline. The consensus of ENSO prediction models indicate weak El Niño conditions during the April-June 2015 season in progress, likely strengthening during summer and lasting through 2015.
INDIAN OCEAN STATE :0.5 degrees C above average temperature was observed around Sri Lanka
MJO STATE :MJO continues to be weak and therefore shall not have a significant impact on the rainfall in Sri Lanka