Weekly Hydro-meteorological Report, 1 January, 2015

Highlights

Monitoring and Prediction

As predicted in the previous week eastern regions of Sri Lanka along with the adjacent sea received extremely heavy rainfall. On the 25th and 26th of December the entire country received rainfall reaching up to 200 mm. Thereafter a decrease in the rainfall was observed. During the next two weeks rainfall is predicted to be lower than the previous weeks, but there shall be high rainfall in the eastern coast.
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Summary

Monitoring


Weekly Monitoring::High precipitation was observed throughout the week 24th – 30th December. On the 24th up to 120 mm rainfall was observed in Kurunegala. On the same day high rainfall was observed in south-eastern region of Sri Lanka while the rest of the country received rainfall up to 50 mm. Highest rainfall during this week was observed on the 25th. Extreme rainfall (up to 200 mm) was observed in Eastern region and the rest of the country received up to 120 mm rainfall except the northern region which only experienced light rainfall. Thereafter rainfall gradually decreased and completely ceased by 30th of December.


Monthly Monitoring:An average rainfall of 16 mm-18 mm was observed throughout the country with higher precipitation observed in the north-eastern regions of Sri Lanka during November. Highest rainfall during this month was observed in Northern and Eastern provinces. Also the decadal rainfall average was increased from 18 mm to 9 mm within a week.

Predictions

14-day prediction:NOAA NCEP models predict a significant decrease in rainfall in coming two weeks (1st- 13th January 2015). But there shall be further heavy rainfall in the eastern coastal region of the country exceeding 135 mm in magnitude.

IMD WRF Model Forecast & IRI forecast:According to the IMD WRF model, central region of the country shall receive rainfall up to 125 mm with the highest expected in Wasgamuwa area on the 2nd of January. Then on the 3rd rainfall shall decrease with most of the country expected to have light showers. Nuwara Eliya region shall receive up to 35 mm rainfall.

Seasonal Prediction:As per IRI Multi Model Probability Forecast issued in November for the season December 2014 to February 2015, Rainfall shall remain climatological while the temperature shall be above normal with about 70% probability.

PACIFIC SEAS STATE December 18, 2014 :During November through early December 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 in Phase 5-Maritime Continent and therefore shall suppress the rainfall in Sri Lanka.