Weekly Hydro-meteorological Report, 10 December, 2015

Highlights:


Heavy rainfall was observed in the entire country during the 1st- 7th December 2015. The Sea around the country also received extremely heavy rainfall during this week. NOAA NCEP models predict a decrease in the rainfall in northern and north central regions of the country but very heavy rainfall shall continue in the eastern region during the next two weeks. The sea surface temperature around the country is neutral. The MJO shall be in phases 5 and 6 during the next week which shall suppress rainfall.
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Weekly Hydro-meteorological Report, 03 December, 2015

Highlights:


Heavy rainfall was observed in the last few days throughout the country due to a low pressure area in the Bay of Bengal. Up to 40 mm rainfall was observed in northern and eastern regions of the country during the time period 25th November – 1st December. Heavy rainfall up to 160 mm was observed in ocean near Puttalam and up to 130 mm in ocean near Trincomalee on 1st December. Rainfall up to 110 mm was observed around Sinharaja Forest Reserve on 30th November. NOAA NCEP models predict rainfall excess of 135 mm in the northern, north central and central regions of the country. The rest of the country too shall receive high rainfall (about 95 mm) Very heavy rainfall is predicted for the area around Badulla in the next few days by IRI CFS models.
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Weekly Hydro-meteorological Report, 26 November, 2015

Highlights:


Up to 40 mm rainfall was observed in northern and eastern regions of the country during 17th-23rd November. Heavy rainfall up to 130 mm was observed in ocean near Mannar on 23rd November and up to 110 mm in ocean near Mullaitivu on 18th November. Rainfall up to 80 mm was observed around northern region of Moneragala and Welioya on 20th November. High rainfall shall continue in northern and north-eastern regions of the country in the next two weeks.
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Weekly Hydro-meteorological Report, 19 November, 2015

Highlights:


Up to 40 mm rainfall was observed in northern, north eastern and north western regions of the country during the time period 10th-16th November. Heavy rainfall up to 180 mm was observed in ocean near Kilinochchi on 13th November and up to 160 mm in Jaffna, Kilinochchi and Mannar island on 15th November. Rainfall up to 100 mm was observed in Giriulla on 12th November. Every prediction model predict increase of rainfall during the next week. Below average sea surface temperature was observed around Sri Lanka
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Weekly Hydro-meteorological Report, 12 November, 2015

Highlights:


Up to 40 mm rainfall was observed in northern, north eastern, north central and southern regions of the country during the time period 4th-10th November. Heavy rainfall up to 120 mm was observed in ocean near Ampara on 9th November and ocean near Jaffna on 8th November. Rainfall up to 80 mm was observed in ocean near Jaffna on 7th November. IRI and IMD models predict a decrease in rainfall in next two weeks but still high rainfall is expected during this period.
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Weekly Hydro-meteorological Report, 05 November, 2015

Highlights:


Up to 40 mm rainfall was observed in northern, north eastern and western regions of the country during the time period 27th October – 2nd November. Heavy rainfall up to 160 mm was observed in Trincomalee on 27th October and Kekirawa on 2nd November. Rainfall up to 120 mm was observed in Mankulam, Punewa, Mihintale and Trincomalee on 1st November. Every prediction model predict increase of rainfall during the next week.
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The Climate Over Sri Lanka up to the Yala 2015

By: Prabodha Agalawatte, Udara Rathnayake, Zeenas Yahiya, Lareef Zubair

Summary

The rainfall from January to March leading up to the 2015 Yala season was slightly lower than normal; the rain picked up in April and May exceeding normal values. Even though the rainfall remained below normal for the rest of the season through August, the water availability was suited for irrigated cultivation such as for rice. North-central region of the country mostly received above average rainfall while south western regions which usually receive high rainfall mostly received below average rainfall. During September the entire country received above average rainfall. Heavy rainfall was observed during last two weeks of September which caused floods in several areas of the country. An El Nino event which had developed to a borderline state for many months became a fully-fledged event by July 2015. Usually during an El Nino, the rainfall is deficient from January to March and June to August. Rainfall in October to December is above normal and in May too is usually above normal. In addition, a positive Indian Ocean Dipole event took place – what this means is that the Arabian sea is warmer than normal in relation to the Bay of Bengal seas surfaces near Sumatra. In positive dipole events, usually there is a weak drop in rainfall from June to August and a significant rise from September to November.  So this years, rainfall is following close to the historical averages for a combined El Nino and positive Indian Ocean Dipole event. In addition to this the amplitude of the Madden Julian Oscillation (MJO) in 2015 has been a mixture of very high amplitude events and weak events. When the amplitude is higher than 1 the rainfall is enhanced or suppressed based on the location of the MJO wave. When it is less than 1 MJO is considered to be weak and there shall not be an impact on rainfall. During March- April and June- July the MJO was strong. During February, May, August- September the MJO was mostly weak. Severe drought conditions were not observed during the early Yala season because most parts of the country observed high rainfall in April and May. Significant below average rainfall was only observed in July 2015.

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