Weekly Hydro-meteorological Report, 18 December, 2014

Highlights

Monitoring and Prediction

Rainfall up to 250 mm is expected in the eastern sea and the eastern coast of Sri Lanka during the next few days. High rainfall was observed throughout the country in the previous week with highest rainfall in South-western region of Sri Lanka as well as in Trincomalee and Polonnaruwa regions. Rainfall shall decrease during next week in the entire country but not in a significant level. The northern sea region of Sri Lanka shows a below average sea surface temperature.
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Summary

Monitoring


Weekly Monitoring::From 9th to 12th December around 20 mm average rainfall was observed throughout the country in general while the Western province has received around 40 mm rainfall. On 13th of December light rainfall was observed around the coastal regions. On 14th and 15th of December significant rainfalls were observed only in Kalutara, Ratnapura, Trincomalee and Polonnaruwa areas. The Western province, Trincomalee and Polonnaruwa has received the highest rainfalls during the week.


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 similar rainfall conditions in the next two weeks compared to previous weeks as well. The entire country shall receive rainfall around 65 mm during 17th to 23rd December. Rainfall shall decrease throughout the country averaging around 35 mm during the week of 24th to 30th December.

IMD WRF Model Forecast & IRI forecast:According to the IMD WRF model, north-eastern, north-central and south-eastern regions shall receive average rainfall up to 35.6 mm on 19th of December. Rainfall is expected to increase significantly throughout the country on 12th of December where Eastern province shall receive up to 64.5 mm – 124.5 mm rainfall. The IRI models predict up to 250 mm rainfall in the eastern sea and up to 200 mm in the eastern coast during 16th- 21st.

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 4, 2014 :During October through November 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 November-January season in progress, continuing well into the northern spring 2015.
INDIAN OCEAN STATE :Around 0.5 degrees C below average sea surface temperature was observed towards the northern coast.
MJO STATE :MJO is weak and therefore shall not influence the rainfall.