Weekly Hydro-meteorological Report, 21, September 2017

Highlights:

•   The WRF model predicts up to 36 mm of total rainfall in the western coastal regions on the 22nd.
•   Between 13 - 19 Sep: Rainfall up to 30 mm was recorded in Jaffna and Kiinochchi districts on the 13th.
•   From 10 - 16 Sep:  minimum temperature of 20 ^OC was recorded from Nuwara Eliya district while most parts of the island recorded a maximum temperature between  30-35 ^OC.
•   From 12 - 18 Sep: up to 54 km/h, southwesterly winds were experienced by the entire country.
•   0.5 ^OC above average sea surface temperature was observed in the northern and eastern  seas around Sri Lanka.

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Summary

Monitoring

Weekly Monitoring: On September 13th, Jaffna and Kilinochchi districts received up to 30 mm of rainfall; Puttalam, Kurunegala, Gampaha, Kegalla, Colombo and Kalutara districts up to 20 mm; and many parts of the island up to 10 mm. On the 14th Gampaha, Colombo, Kegalla and Ratnapura districts received up to 10 mm of rainfall. On the 15th Ampara and several regions of Monaragala districts received up to 10 mm of rainfall. On the 16th Kalutara, Galle and Ratnapura districts received up to 20 mm of rainfall; and many southwestern parts of the island up to 10 mm. On the 17th Kurunegala district received up to 20 mm of rainfall; and many central and western parts of the island up to 10 mm. No significant rainfalls were recorded in any part of the island during 18th and 19th.

Total Rainfall for past week :  The RFE 2.0 tool shows total rainfall of 25-50 mm in Puttalam, Kurunegala, Kalutara and Ratnapura districts; and 25-50 mm Kegalla, Matale, Kandy, Nuwara Eliya, Galle and Matara districts. It shows below average rainfall up to and 10-25 mm in Trincomalee, Anuradhapura, Polonnaruwa, Badulla, Monaragala, Galle, Matara and Hambantota districts.

Monthly Monitoring: During August - below average rainfall conditions were experienced in the southern and western regions of the island and above average rainfall in northern and eastern regions. Gampaha, Colombo, Kalutara, Galle, Matara, Kegalla, Nuwara Eliya and Hambantota districts received up to 150 mm below average rainfall. Batticaloa, Ampara and Monaragala districts received up to 180 mm of above average rainfall; and Mannar, Anuradhapura, Polonnaruwa, Trincomalee, Ampara and northern regions of Puttalam and Badulla districts up to 150 mm. The CPC Unified Precipitation Analysis tool shows ~300 mm of total rainfall in Batticaloa, Polonnaruwa, Monaragala, Badulla, Ratnapura, Anuradhapura and Ampara districts; up to ~200 mm in Trincomalee, Puttalam, Matale, Kandy, Kalutara and Galle districts; up to 100 mm in Jaffna, Kilinochchi, Mullaitivu, Kurunegala, Matara and Hambantota districts; and up to 50 mm in many parts of the island.

Predictions

14-day prediction:
NOAA NCEP Models:
From 20th – 26th Sep: Total rainfall between 45-55 mm in Colombo, Kegalla, Ratnapura and Galle districts; and between 35-45 mm Gampaha, Kurunegala and Matara districts.
From 27th Sep – 3rd Oct :  Total rainfall between 65-75 mm in Kalutara and Galle districts; between 45-55 mm in Colombo, Kegalla, Ratnapura and Matara districts; and between 35-45 mm Puttalam, Gampaha, Kurunegala and Hambantota districts.

IMD WRF Model Forecast: 
  22nd  Sep: Up to 36 mm of rainfall in Puttalam, Gampaha, Colombo, Kalutara, Galle and Ratnapura districts; and up to 7.6 mm in many parts of the island.
  23rd Sep: Up to 7.6 mm of rainfall in Kilinochchi, Mulaitivu, Mannar, Anuradhapura, Polonnaruwa, Puttalam, Gampaha, Colombo, Kalutara, Galle and Hambantota districts.

IRI Weekly forecast:
20th- 25th Sep: Total rainfall up to 50 mm in northern coastal regions of Jaffna district.


Ocean State (Text Courtesy IRI)
PACIFIC SEAS STATE : September 19, 2017
In mid-September 2017, the tropical Pacific remained in an ENSO-neutral state, although SSTs in the east-central tropical Pacific have cooled to the threshold for La Niña while the atmosphere continues to maintain largely ENSO-neutral patterns. The collection of latest ENSO prediction models indicates coolish ENSO-neutral or weak La Niña as two possible scenarios during Northern Hemisphere fall and winter. The official CPC/IRI outlook slightly favors La Niña development, and carries a La Niña watch.

INDIAN OCEAN STATE :   0.5 ⁰C above average sea surface temperature was observed in the northern and eastern  seas around Sri Lanka.

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