Weekly Hydro-meteorological Report, 16, June 2016

Highlights: Previous week was dry except rainfall during 8th -9th and 12th of June mostly in the south western region. The highest rainfall up to 90 mm was seen around Balangoda on the 9th. The Temperature was highest (35- 40 0C) in the eastern coastal area and was lowest in the hill country (15- 20 0C) in the previous week. NOAA NCEP models predict up to 135mm total rainfall in south western region in the next week while other regions shall have up to 85mm rainfall. NOAA CPC GFS model predicts 35- 40 0C maximum temperature along the coastal region between Kilinochchi and Hambantota during the next week. Higher wind speed (up to 20 m/s) is expected in the southern regions and the sea. MJO shall be in the Indian Ocean and shall contribute to enhance the rainfall in the region.

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Monitoring
Rainfall

Weekly Monitoring:On the 8^th, up to 50 mm rainfall was received in eastern region of Colombo and the sea west to Puttalam. Balangoda and surrounding regions experienced the highest rainfall of the week as 90 mm on the 9^th while up to 60 mm rainfall was seen in Gampaha. No significant rainfall was received during 10^th-11^th June in the entire country and again up to 80 mm rainfall was seen around southern region of Puttalam and Kurunegala on the 12^th. No rainfall was recorded during 13^th-14^th June as well. Based on the CPC Unified Precipitation Analysis, up to 75 mm total rainfall was seen in south western region of the country while surrounding regions received up to 55 mm rainfall during the week. According to the RFE 2.0 model, between 50-100 mm total rainfall was received in western and south western regions of the country within the week while the surrounding regions experienced up to 25 mm total rainfall. It recorded up to 25 mm of total rainfall anomaly in western province, Kurunegala district and nearby cities.

Monthly Monitoring:Entire country received more rainfall than the historical average during May 2016. The districts in western, north western and north central provinces received up to ~450mm monthly excess rainfall than the historical average. CPC Unified Precipitation Analysis recorded up to 500 mm total rainfall in south western region while 150-300 mm total rainfall in the rest of the country except Uva and eastern provinces. According to RFE 2.0 model, up to 750 mm of total monthly rainfall was received around Kegalle and Gampaha while the surrounding regions experienced up to 500 mm total rainfall during the month. Puttalam and Anuradhapura received 6 times more rainfall than the historical average and northern, central and western provinces received 4 times more rainfall. Nearly 140 mm of accumulated average monthly precipitation was recorded as above normal historical average during 17^th May- 13^th June while the highest daily average precipitation in the entire country was recorded as 50 mm on the 17^th. 

Temperature

The highest maximum temperature was seen along northern and eastern sea as 35- 40 ⁰C during 5^th- 11^th June. Kandy and Nuwara Eliya region experienced low maximum temperature as 20 ⁰C while the maximum temperature in the rest of the country was between 30- 35 ⁰C. Entire country has experienced 25- 30 ⁰C of minimum temperature except Kandy, Nuwara Eliya, Ratnapura and surrounding districts. The mean temperature in South western, northern and central regions of the country was between 1⁰C- 3 ⁰C during this week. 

Wind

Entire country experienced 15 m/s total westerly wind at the 850 mb level during the previous week while northern region received up to 10 m/s wind in the same direction at the 700 mb level and 6-10 m/s in the rest of the country.

  

Ocean State

Pacific seas state: May 19, 2016

During early June 2016 the tropical Pacific SST anomaly turned weakly negative, now indicating cool-neutral ENSO conditions. Most of the atmospheric variables have also stopped supporting an El Niño pattern. This includes now near-average upper and lower level tropical Pacific winds, as well as near-normal cloudiness and rainfall patterns in the central and eastern Pacific. Most ENSO prediction models indicate neutral ENSO conditions during June, with likely development of La Niña (of unknown strength, but likely weak) by late July or August, lasting through fall and into winter. (Text Courtesy IRI)

Indian Ocean State

0.5⁰C above average sea surface temperature was observed around Sri Lanka.

Predictions

14-day prediction:NOAA NCEP models predict more than 135mm total rainfall in south western and western regions while surrounding regions shall experience up to 115 mm total rainfall during 15^th- 21^st June. Total rainfall shall decrease during 22^nd– 28^th June. Up to 125 mm total rainfall is expected around Kegalle and Colombo districts while close by regions shall have up to 115 mm total rainfall.  The rest of the country shall have up to 85 mm of total rainfall except south eastern region within the same week.

Weekly prediction: IMD GFS model predicts up to 40mm rainfall in south western region of the country during 16^th -18^th June while surrounding regions of Galle shall have up to 70 mm rainfall on the 19^th. Up to 70mm rainfall is expected around Kalutara and Colombo districts while surrounding cities shall have up to 40 mm rainfall during 20^th-21^st June. The rainfall shall decrease in the south western region in the 22^nd as up to 40 mm.

IMD WRF Model Forecast & IRI forecast:According to the IMD WRF model, there shall be up to 65mm rainfall near Ratnapura and Kalutara districts while rest of western and south western regions shall receive up to 35 mm rainfall on the 17^th. There shall be up to 125 mm rain around Ratnapura, Kegalle and Nuwara Eliya districts on the 18^th while surrounding regions may receive up to 65 mm rainfall. According to IRI CFS model, rainfall shall increase than the previous week as up to 100 mm total rainfall in surrounding regions of Colombo and Kalutara districts while Gampaha, Kegalle, Ratnapura and Galle districts shall have up to 75 mm total rainfall during 13^th -18^th June.

 Seasonal Prediction:As per IRI Multi Model Probability Forecast for July to September, 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.

Temperature

NOAA CPC GFS model predicts 35- 40 ⁰C maximum temperature along the coastal region between Kilinochchi and Hambantota and 30- 35 ⁰C maximum temperature along north, central and south of the country. Maximum temperature in the hill country shall be between 20- 25 ⁰C. During the same week, minimum temperature is expected around Nuwara Eliya, Ratnapura and Badulla to be 15- 20 ⁰C while in Uva, Central, Sabaragamuwa and Western provinces it shall be 20- 25 ⁰C.

Wind

The wind speed shall increase up 20 m/s in Western, Sourthern and Sabaragamuwa provinces as well as the southern sea during 16^th – 22^nd June which was in the 10- 15 m/s range in the previous two weeks. The wind speed shall be 10- 15 m/s in other regions and sea areas in Sri Lanka. The wind direction shall generally be westerly.

MJO based OLR predictions

MJO is in phase 2 on the 14^th, and continue to stay in the Indian ocean region during the next 15 days. This shall enhance rainfall conditions in Sri Lanka.