Weekly Hydro-meteorological Report, 25 September, 2014

Highlights

Monitoring and Prediction

Heavy rainfall is expected in the entire country during the next week. Badulla, Moneragala and Polonnaruwa districts shall receive heaviest rainfall during this period.
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Summary

Monitoring


Weekly Monitoring::On the 17th and 18th of September only light rainfall was observed in south western parts of Sri Lanka. No rainfall was observed anywhere in the country on the 19th and the 20th. Up to 10 mm rainfall was observed in the north central region on the 21st and in the central region on the 22nd. The entire western half of the country received much higher rainfall compared to previous days on the 23rd with Galle and Matara areas receiving rainfall up to 120 mm.


Monthly Monitoring:An above average rainfall was observed throughout the country with higher precipitation observed in the south-western regions of Sri Lanka during August. Highest rainfall during this month was observed in Ratnapura district.

Predictions

14-day prediction:The entire country shall receive total rainfall up to 55 mm during 24th September to 7th October.

IMD WRF Model Forecast & IRI forecast: According to the IMD WRF model the entire country shall receive high rainfall on the 26th of September. Most of the country shall receive up to 35 mm rainfall with exceptions of north eastern region, which shall receive up to 125 mm rainfall, and south eastern region, which shall receive up to 7.5 m rainfall. On the 27th a decrease in rainfall is expected in most places. North eastern region shall receive rainfall up to 65 mm and Anuradhapura and surrounding region shall receive rainfall up to 125 mm. South western and western regions shall receive light rainfall and the rest of the country except south eastern region shall receive rainfall up to 7.5 mm. NOAA models also predict very high rainfall in Polonnaruwa during 24th- 29th September. During this period the Uva Province shall receive total rainfall up to 200 mm.

Seasonal Prediction:As per IRI Multi Model Probability Forecast issued in September for the season October to December 2014, Rainfall shall remain climatological while the temperature shall be above normal with a high probability.

PACIFIC SEAS STATE September 18, 2014 :During August through early September the observed ENSO conditions moved to those of a borderline El Niño. Most of the ENSO prediction models indicate weak El Niño conditions during the September-November season in progress, strengthening slightly and peaking at weak strength during winter 2014-15 and lasting into the first few months of 2015.
INDIAN OCEAN STATE :Around 0.5 degree Celcius above average sea surface temperature was observed around Sri Lanka.
MJO STATE :MJO is weak and therefore shall not influence the rainfall in Sri Lanka.