Weekly Hydro-meteorological Report, 23 April, 2015

Highlights


Heavy rainfall continued in the western side of the country with Kaluthara and Galle districts receiving more than 250 mm rainfall in the past week. In addition to this Kurunegala, Puttalam, Colombo, Gampaha, Kegalle districts also received heavy rainfall. According to NOAA predictions the south western regions shall receive more rainfall in the next two weeks.
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Summary

Monitoring


Weekly Monitoring::Rainfall was observed throughout the country during 14 th - 18 th April 2015 with the magnitude reaching up to 30 mm. No observation is available for the 19 th . On the 20 th extremely heavy rainfall was observed in the western side of the country and the western sea. Up to 100 mm rainfall was observed in Kurunegala, Puttalam, Kegalle and Gampaha districts and up to 220 mm rainfall was observed in Colombo, Kaluthara and Galle districts on the 20 th .


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 south western regions of 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 25 th and 26 th of April. On the 25 th Central, North central and south western regions of the country shall receive 35 mm rain. On the 26 th up to 35 mm rainfall is expected in the eastern region in addition to central and north central regions. NOAA CFS model also predict heavy rainfall in the central regions of the country.

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