Weekly Hydro-meteorological Report, 30 April, 2015

Highlights


The entire country received heavy rainfall during 22 nd - 28 th April but not continuously. Mre rainfall was observed on the western side of the country compared to the eastern side. Heavy rainfall is once again predicted in the region around Badulla by IRI CFS models. The MJO remained in a weak state for the third continuous week and therefore shall not influence the rainfall in Sri Lanka.
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Summary

Monitoring


Weekly Monitoring:: On the 22 nd April only light rainfall was observed in the central region of Sri Lanka. Then on the 23 rd rainfall increased up to 100 mm in Kandy, Ratnapura and Kegalle districts and up to 30 mm rainfall was observed in Vavuniya and Kilinochchi districts. On the 24 th the entire country except for eastern regions of the country received up to 80 mm rainfall. A decrease in rainfall was observed on the 25 th but central to Uva regions continued to receive up to 50 mm rainfall. The western side along with northern regions of the country received heavy rainfall on the 26 th with rainfall in Kurunegala exceeding 100 mm. Then once again relatively low rainfall was observed on 27 th and 28 th in the entire country except in north central region which received up to 30 mm rainfall during these two days


Monthly Monitoring: In March 2015 the western side of the country received above average rainfall averaging up to 12 mm/day while the rest of the country received below average rainfall. During the first ten days of April heavy rainfall was observed on the western half of Sri Lanka. Thereafter during the next ten days the rainfall further increased with extremely heavy rainfall received by Kaluthara and Galle districts.

Predictions

14-day prediction: NOAA NCEP models predict high rainfall in the entire the country during the next fortnight.

IMD WRF Model Forecast & IRI forecast: According to the IMD WRF model, the entire country shall receive rainfall on the 1 st of May. On this day western coastal regions and Ratnapura area shall receive up to 35 mm rainfall. This may go up to 65 mm in Negombo to Puttalam area. Rainfall shall decrease on the 2 nd of April.

Seasonal Prediction:As per IRI Multi Model Probability Forecast for April to June, 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 April 16, 2014 :During March through early April 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 AprilJune 2015 season in progress, likely strengthening during summer and lasting through 2015
INDIAN OCEAN STATE :Neutral sea surface temperature was observed in the sea immediately around Sri Lanka.
MJO STATE :MJO continues to be weak and therefore shall not have a significant impact on the rainfall in Sri Lanka