Weekly Hydro-meteorological Report, 1 October, 2015

Highlights:


Up to 40 mm rainfall was observed in south western, western and north eastern regions of the country during the time period 22nd-28th September. Ocean near Kalutara received heavy rainfall up to 160 mm on 25th September and Galle received heavy rainfall up to 120 mm on 28th September. Every prediction model predict decrease of rainfall during the next week.
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Summary

Monitoring


Weekly Monitoring: During 22nd -28th of September, eastern and south western regions of the country received heavy rainfall. On 22nd September only Badulla received rainfall up to 30 mm and on 23rd southern regions of Matale, Kandy and Ratnapura received rainfall up to 30 mm. Rainfall up to 45 mm was observed in Mannar and eastern regions of Anuradhapura, Vavuniya, Mullaitivu and northern regions of Puttalam and Kurunegala. Heavy rainfall up to 160 mm was observed in the ocean near Kalutara while western province received rainfall up to 90 mm and Badulla, Nuwara-Eliya also received rainfall up to 50 mm on 25th September. On 26th September Trincomalee received rainfall up to 100 mm and Colombo received rainfall up to 80 mm while south eastern region also received rainfall up to 50 mm. On 27th September, ocean near Galle received rainfall up to 80 mm and Polonnaruwa, Matale and northern region of Ampara received rainfall up to 50 mm. On 28th September, coastal region of Galle received rainfall up to 120 mm while Matara received rainfall up to 90 mm.


Monthly Monitoring::In August 2015 most of south western, north western and north central regions received above average rainfall. Colombo district, central and eastern provinces received below average rainfall. Highest rainfall was observed in Ratnapura district. Southern sea of the country also received above average rainfall during this month.

Predictions

14-day prediction: NOAA NCEP models predict high rainfall in all regions of the country except south eastern during 30th September-6th October. Total rainfall up to 45 mm is expected during the week. These models predict that the rainfall shall increase during 7th- 13th October and total rainfall up to 85 mm is expected in south western region and the rest of the country shall receive total rainfall up to 45 mm.

IMD WRF Model Forecast & IRI forecast: According to the IMD WRF model heavy rainfall up to 125 mm shall receive in the ocean near Mannar on 02nd October while eastern region shall receive rainfall up to 35 mm. The rest of the country shall also receive slight amounts of rainfall. Rainfall shall be decreased by 03rd October and only few regions in eastern province shall receive rainfall up to 35 mm and rest of the country shall not receive significant amount of rainfall. IRI CFS models predict total rainfall up to 60 mm in northern and north eastern regions of the country during 30th September-05th October.

Seasonal Prediction:As per IRI Multi Model Probability Forecast for October to December, the total 3 month precipitation has 50% likelihood of being above average. 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 September 17, 2015 :During late August through early September 2015 the tropical Pacific SST was at a strong El Niño level. All atmospheric variables support the El Niño pattern, including weakened trade winds and excess rainfall in the east-central tropical Pacific. The consensus of ENSO prediction models indicate continuation of strong El Niño conditions during the September-November 2015 season in progress. Some further strengthening into later fall is possible, with the event lasting well into spring 2016.
INDIAN OCEAN STATE : 1 0C above average temperature was observed around Sri Lanka.Indian Ocean Dipole is also active.
MJO STATE :MJO phase is in 2 therefore shall slightly enhance rainfall in Sri Lanka.