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Friday, January 6, 2017

Weekly Hydro-meteorological Report, 5, January 2017


  •  The NCEP GFS model predicts no rainfall over Sri Lanka for next week.  
  •  Between 28 Dec–3 Jan: highest rainfall of 70 mm was recorded on the 31st in Ratnapura town.
  •  From 27 Dec–2 Jan: minimum temperature of 15 OC was recorded from Nuwara Eliya district while many parts of the island recorded a maximum temperature between 30-35 OC.
  •  From 27 Dec–2 Jan: up to 28 km/h north easterly winds were experienced in the southern and central regions of the island and speeds less than 20 km/h in the northern regions.

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Weekly Monitoring: On December 28th Colombo district received up to 50 mm of rainfall; Gampaha district up to 40 mm; Kalutara, Galle, Kegalla, Ratnapura, Monaragala, Ampara and Kurunegala districts up to 30 mm; and Batticaloa, Polonnaruwa, Kandy, Matale and Badulla districts up to 20 mm of rainfall. No significant rainfalls were recorded within the island on 29th and 30th. On the 31st Ratnapura district received up to 70 mm of rainfall; Kalutara district up to 30 mm; and Kegalla, Kandy and Galle districts received up to 20 mm of rainfall. On the 1st of January adjacent south eastern sea received up to 50 mm of rainfall. On the 2nd Ampara and Batticaloa districts received up to 20 mm of rainfall. No significant rainfalls were recorded on the 3rd.

Total Rainfall for past week : The RFE 2.0 tool shows total rainfall up to 100 mm for Ratnapura district; up to 50 mm for Gampaha, Colombo, Kalutara, Kegalla, Batticaloa, Ampara, Badulla, Kurunegala, Matale, Nuwara Eliya and Galle districts; and up to 25 mm for Puttalam, Kandy, Hambantota and Matara districts. It shows above average rainfall of 50-100 mm for Ratnapura district; 10-25 mm for Kurunegala, Gampaha, Colombo, Kalutara and Kegalla districts; below average rainfall of 25-50 mm for Batticaloa, Ampara and Anuradhapura districts; and 10-25 mm for many parts of the island.

Monthly Monitoring:During December – below average rainfall conditions were experienced by the entire island. Eastern regions of the island received up to 240 mm below average rainfall; and up to 150 mm in rest of the country. Monthly average rainfall for Colombo, Kalutara, Galle and Ratnapura amounted to 360 mm/month; and 180 mm/month for many parts of the island. The CPC Unified Precipitation Analysis tool shows ~200 mm of total rainfall in the coastal regions of Colombo district; ~100 mm in Kalutara, Galle, Ratnapura, Kegalla, Kandy, Matale, Ampara, Badulla and Monaragala districts; and ~50 mm in rest of the island.


14-day prediction:
From 4th – 10th Jan: No rainfall.
From 11th – 17th Jan: Total rainfall between 10-15 mm in Colombo, Kegalla and Ratnapura districts.

IMD WRF Model Forecast & IRI forecast:
 6th Jan: Up to 3 mm of rainfall in Kinniya and Agbopura in Trincomalee district.
 7th Jan: Up to 3 mm of rainfall along the coastal regions of the Batticaloa district.

Seasonal Prediction: As per IRI Multi Model Probability Forecast for January to March 2017, the total 3-month precipitation has 40-50% likelihood of being in the above-normal tercile for the whole island. The 3-month temperature has more than 70-80% likelihood in the entire country of being in the above-normal tercile during this period.

Ocean State (Text Courtesy IRI)
PACIFIC SEAS STATE : December 15, 2016
During mid-December 2016 the tropical Pacific SST anomaly was near -0.5C, the threshold for weak La Niña. Also, most of the atmospheric variables across the tropical Pacific have been consistent with weak La Niña conditions, although sub-seasonal atmospheric variability weakened some of them in late November. The upper and lower atmospheric winds have been suggestive of a strengthened Walker circulation, and the cloudiness and rainfall have also been consistent with weak La Niña conditions. The collection of ENSO prediction models indicates SSTs near the threshold of La Niña persisting through mid-winter, then weakening to cool-neutral by later winter.

INDIAN OCEAN STATE : 0.5 OC above average sea surface temperature was observed in the southern seas of Sri Lanka.

MJO STATE : MJO shall enhance the rainfall in Sri Lanka for the next 10 days and shall not have a significant impact in the following 5 days.

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