Weekly Hydro-meteorological Report, 31 December, 2015

Highlights:


Slight decrease of rainfall was observed in the entire country in the week 23rd – 29th December. Highest rainfall was observed in western region of Kilinochchi and the ocean near Delft Island on 27th December. Relatively high rainfall was observed in several regions in Matale, Moneragala and Badulla. NOAA NCEP models predict increase of rainfall during next week. MJO phase is in 6 and shall continue to slightly suppress rainfall of the country.
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Summary

Monitoring


Weekly Monitoring:Slight amounts of rainfall observed in the country during 23rd – 29th December. On 23rd and 24th December, no rainfall was observed in entire country. On 25th Galle and Matara districts received rainfall up to 20 mm. Galoya national park received rainfall up to 50 mm on 26th December while Avissawella, north eastern region of Kandy and Horowpotana received rainfall up to 30 mm. On 27th December heavy rainfall was observed (up to 170 mm) in western region of Kilinochchi and ocean near Delft island received rainfall up to 160 mm while ocean near Jaffna received rainfall up to 100 mm and Laggala, Hettipola, Thanamalvila and Badulla received rainfall up to 90 mm. Rainfall up to 90 mm was observed around somawathie chaithya sanctuary on 28th December. Rainfall up to 60 mm was observed in eastern region of Kandy on 29th December while Kuliyapitiya received rainfall up to 50 mm.


Monthly Monitoring::In November 2015, almost entire country received above average rainfall while the ocean near eastern and southern provinces, southern region of Galle and Matara received below average rainfall. Higher above average rainfall was observed in northern region compared to southern region of the country.

Predictions

14-day prediction: NOAA NCEP models predict decrease of the rainfall during 30th December – 5th January compared to past weeks where heavy rainfall was observed. Total rainfall up to 35 mm is expected during the week in western region and total rainfall up to 25 mm is expected in rest of the country. These models predict the rainfall to increase during 6th – 12th January 2016 where eastern region shall receive rainfall up to 95 mm and rest of the country is expected to receive total rainfall up to 55 mm.

IMD WRF Model Forecast & IRI forecast: According to the IMD WRF model, eastern region of the country shall receive rainfall up to 35 mm on 1st January while the rest of the country shall receive slight amounts of rainfall. On 25th December, eastern region of the Kilinochchi shall receive rainfall up to 65 mm and eastern region shall receive rainfall up to 35 mm and rest of the country shall receive slight amounts of rain. IRI CFS models predict total rainfall up to 75 mm off the coast of Batticaloa during 30th December – 4th January.

Seasonal Prediction:As per IRI Multi Model Probability Forecast for January to March, the total 3 month precipitation has 50% likelihood of being below average. 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 December 17, 2015 :During mid-December 2015 the tropical Pacific SST was at a strong El Niño level. All atmospheric variables strongly support the El Niño pattern, including weakened trade winds and excess rainfall in the east-central tropical Pacific. The consensus of ENSO prediction models indicate continuation of strong El Niño conditions during the December-February 2015-16 season in progress. Further strengthening is possible, but unlikely, into mid-winter 2015-16, with the event slowly weakening during spring 2016.
INDIAN OCEAN STATE : 1.5 degree Celsius above average sea surface temperature was observed around Sri Lanka.
MJO STATE :MJO is in phase 5 therefore shall slightly suppress rainfall in Sri Lanka.