Weekly Hydro-meteorological Report, 21, April 2016

Highlights:


Rainfall received in central, southern, western and south western regions of the country during 13th-19th April. Highest rainfall of 70 mm was seen in Moratuwa and near Kurunegala town on 19th April and very less rainfall received in northern and eastern regions of the country during the previous week. NOAA NCEP models predict up to 45 mm total rainfall in south western region of the country while IRI CFS model predicts up to 50 mm total rainfall around Badulla during 20th– 26th April. MJO is weak so there shall be no effect on rainfall by the MJO.
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Summary

Monitoring


Weekly Monitoring:Rainfall received in central, southern, western and south western regions of country during 14th – 19th April and no rainfall was seen on 13th April. On the 14th, southern region of Kegalle, Katugastota, northern region of Kalutara and Ratnapura received up to 20 mm rainfall. Up to 60 mm rainfall was seen in Nittambuwa on the 15th, while Balangoda and southern region of Nuwara Eliya received rainfall up to 50 mm. On the 16th, Ratnapura town, Kurunegala town, Gampaha and surrounding regions received up to 30 mm rainfall. Central region of Ratnapura received rainfall up to 60 mm while Balangoda, central region of Gampaha and southern sea of the country received up to 30 mm rainfall on 17th. Only light rainfall was seen on 18th April throughout the country but up to 20 mm rainfall was seen the sea west of Puttalam, south of Matara and Hambantota. On the 19th, up to 70 mm rainfall was seen close to Kurunegala town and Moratuwa while up to 50 mm rainfall in Colombo, western regions of Kegalle and Kalutara, eastern region of Gampaha, northern region of Ratnapura, Kurunegala districts and the western sea region of the country.


Monthly Monitoring:During March 2016 most regions of the country received below average rainfall. Rainfall received by Ratnapura, Kalutara, northern regions of Colombo and Galle, western and southern regions of Puttalam was about 10 mm/day less than the historical average for this month. Above average rainfall was only seen in Kegalle, Kandy, Matale districts and the south eastern region of Kurunegala district.

Predictions

14-day prediction:NOAA NCEP models predict up to 45 mm total rainfall in the south western region of the country during 20th – 26th April and 27th April – 3rd May.

IMD WRF Model Forecast & IRI forecast:According to the IMD WRF model, up to 35 mm rainfall is expected near Vavuniya and Anuradhapura on 22nd of April while the rest of the country shall receive a slight rainfall. The models predict up to 35 mm rainfall close to Ratnapura on 23rd April. IRI CFS model predicts up to 50 mm total rainfall around Badulla during 20th – 25th April.

Seasonal Prediction:As per IRI Multi Model Probability Forecast for May to July, the total 3-month precipitation shall be climatological. 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 April 14, 2016 :During early April 2016 the tropical Pacific SST anomaly was weakening, and becoming a moderate rather than strong El Niño. All atmospheric variables continue to support the El Niño pattern, but at a somewhat weakened strength. This includes weakened trade winds and excess rainfall in the east-central tropical Pacific, extending eastward more weakly than last month. Most ENSO prediction models indicate continued weakening El Niño conditions during the northern spring season, returning to neutral by late spring or early summer 2016, with a chance for La Niña development by fall.
INDIAN OCEAN STATE :1 degrees C above average sea surface temperature was observed around Sri Lanka.
MJO STATE :MJO is weak and therefore it shall not affect the rainfall.