Weekly Hydro-meteorological Report, 21, April 2017

Highlights:

•  The WRF model predicts up to 35 mm of rainfall in Colombo district on 21^st of April.
•   Between 12-18 Apr: highest rainfall of 60 mm was recorded on the 12^th in Colombo district.
•   From 9-15 Apr: minimum temperature of 15 ⁰C was recorded from Nuwara Eliya district while northern regions of the island recorded a maximum temperature between 30-35 ⁰C.
•   From 11-17 Apr: up to 18 km/h, northeasterly winds were experienced by the southern regions, and speeds less than 7 km/h in the northern and central regions of the island.
•   Average sea surface temperature was observed in the seas around Sri Lanka.

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Summary

Monitoring

Weekly Monitoring: On April 12th Colombo district received up to 60 mm of rainfall; and Kalutara, Ratnapura, Galle, Matara and Hambantota districts up to 50 mm; Gampaha district up to 30 mm; and Kalutara, Ampara, Monaragala and Badulla districts received up to 20 mm. On the 13th Kaluatara, Galle, Ratnapura, and Hambantota districts received up to 50 mm of rainfall; Anuradhapura, Kandy, Nuwara Eliya, Badulla, Monaragala, and Matara districts up to 30 mm; and Kurunegala, Matale, Gamapaha, Colombo, Kegalla and Ampara districts up to 20 mm. On the 14th several regions of Polonnaruwa, Trincomalee, Ampara and Monaragala districts received up to 10 mm of rainfall. No significant rainfalls were recorded in any part of the island during the period of 15th-18th.

Total Rainfall for past week :  The RFE 2.0 tool shows total rainfall up to 75 mm for Kalutatara, Ratnapura, Galle, Matara and Hambantota districts; up to 50 mm for Gampaha, Colombo, Kegalla, Nuwara Eliya, Badulla and Monaragala districts; and up to 25 mm for Puttalam, Kurunegala, Anuradhapura, Polonnaruwa, Matale, Kandy, Badulla, Monaragala and Ampara districts. It shows below average rainfall of 50-100 mm for Kurunegala, Matale, Gampaha, Kegalla and Badulla districts; and 25-50 mm for many parts of the island.

Monthly Monitoring: During March - above average rainfall conditions were experienced in the entire island except for Hambantota district, which received up to 90 mm of below average rainfall. Anuradhapura, Kurunegala and Kandy received up to 150 mm above average rainfall; and many parts of the island received up to 120 mm. Monthly average rainfall for Anuradhapura, Matale, Polonnaruwa, Kurunegala, Gampaha, Colombo, Ratnapura, Kegalla, Nuwara Eliya Kandy and Badulla districts amounted to 270 mm/month; and 180 mm/month for many parts of the island. The CPC Unified Precipitation Analysis tool shows ~500 mm of total rainfall in Kurunegala, Gampaha, Colombo, Kegalla, Kandy and Ratnapura districts; up to ~300 mm in Kandy, Anuradhapura, Polonnaruwa, Puttalam, Kalutara, Galle, Badulla, Monaragala, Nuwara Eliya and Matale districts; up to ~200 mm Vavuniya, Mannar, and Matara districts; and up to 150 mm for the rest of the island.

Predictions

14-day prediction:
NOAA NCEP Models:
From 19th – 25th Apr: Total rainfall up to 25-35 mm in Kurunegala, Kegalla, Colombo, Ratnapura and Galle districts; up to 15-25 mm in Anuradhapura, Puttalam, Gamapaha, Matale, Kandy, Nuwara Eliya and Hambantota districts..
From 26th Apr – 2nd May: Total rainfall up to 25-35 mm in Kurunegala, Kegalla, Colombo, Ratnapura, Galle and Matara districts; up to 15-25 mm in Anuradhapura, Puttalam, Matale, Kandy, Nuwara Eliya, Badulla, and Monaragala districts.

IMD WRF Model Forecast & IRI forecast:
  21st Apr: Up to 36 mm rainfall in Colombo district; up to 8 mm rainfall in Gampah, Kalutara and Kegalla districts.
  22nd Apr: Up to 3 mm rainfall in Gampaha and Puttalam districts.

Seasonal Prediction:  April to June: the total 3-month precipitation shall be climatological for the whole country. The 3-month temperature has more than 60-70% likelihood in the western coastal regions and 70-80% likelihood in the rest of the island of being in the above-normal tercile.

Ocean State (Text Courtesy IRI)
PACIFIC SEAS STATE : April 13, 2017
By early April 2017, the tropical Pacific remained in an ENSO-neutral state, with above-average SSTs present in the eastern Pacific Ocean, and near-average SSTs present across the central and east-central part of the basin. Across the western and central Pacific, the pattern of cloudiness, rainfall, and winds remains consistent with La Nina-like conditions. The official forecast and most ENSO prediction models suggest an increasing chance of El Nino into the summer and fall of 2017.

INDIAN OCEAN STATE : Average sea surface temperature was observed in the seas around Sri Lanka.

MJO STATE : MJO shall suppress the rainfall in Sri Lanka.