Weekly Hydro-meteorological Report, 02 April, 2015

Highlights


Both dry and wet conditions were observed during the past week (23 rd March – 29th March). The IMD WRF model predicts 3-day rainfall throughout the country ranging between 1–60 mm from 31 st March – 13th April 2015. NCEP GFS model predicts dry conditions from 31 st - 6th April; and precipitation between 15-25 mm from 7th – 14th April.
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Summary

Monitoring


Weekly Monitoring::No rainfall was observed in any part of the country from 23 rd to 25 th March 2015. Some rainfall was observed through 26 th to 29 th March. On the 26 th apart from the north-western, northcentral, and parts of northern and eastern provinces the whole country received rainfall ranging between 5-40mm, with south-western & north-eastern parts of the country receiving 25–35mm. On the 27 th fairly scattered rainfall was received throughout the country with Northern part of the country receiving rainfall between 5–25mm. On the 28 th parts of Uva, Sabaragamuwa and Southern provinces had received 25-75mm of rainfall while other parts of the country received rainfall varying from 5-25mm. On the 29 th scattered rainfall was observed throughout the country ranging between 5-25mm.


Monthly Monitoring:Most of the country received above average rainfall during February. Less than average rainfall was observed only in Puttalam, Kurunegala, and Polonnaruwa districts. Batticaloa and Ratnapura areas received the highest rainfall during this month. In March until the 10 th , rainfall was mostly observed in the Western, South-western and North-western regions of the country. During the next 10 days rainfall was observed throughout the country with higher rainfall in the Western regions.

Predictions

14-day prediction: NOAA NCEP models predict rainfall for up to 15 mm from 31 st March-6 April 2015. Thereafter 45mm of rainfall is expected from 7 th - 13 th April 2015.

IMD WRF Model Forecast & IRI forecast: According to the IMD WRF model, on the 2 nd of April rainfall is expected throughout the country, with rainfall increasing between 35-60mm in the central, Sabaragamuwa, Western, and part of North-western regions. Rainfall is expected to shift towards Central, North-central, Uva, and Eastern regions on the 3 rd and shall receive between 35-50mm rainfall, and the rest of the country shall also receive slight rainfall. From 31 st March – 5 th April 2015, NOAA/CFS models predict more than 100mm of rainfall in Badulla district and rainfall ranging between 50-100mm in adjacent districts, with rainfall around 25-50mm towards Eastern, North-eastern, Western, and Southern areas. However extreme rainfall events are not predicted during this period.

Seasonal Prediction:As per IRI Multi Model Probability Forecast for April to June, the total 3 month precipitation shall be climatological. The 3 month average temperature has more than 60- 70% likelihood of being in the above-normal tercile during this period.

PACIFIC SEAS STATE March 19, 2014 :During February through midMarch 2015 the SST just met the thresholds for weak Niño conditions. During the last month, some of the atmospheric variables began indicating an El Niño pattern more than they had been earlier, including trade wind weakening and excess rainfall migrating farther to the east. The consensus of ENSO prediction models indicate weak El Niño conditions during the March-May 2015 season in progress, continuing and strengthening El Niño toward mid-2015.
INDIAN OCEAN STATE :Neutral sea surface temperature was observed in the sea immediately around Sri Lanka but the Arabian Sea and South of the Equator is unusually warm. Rainfall is usually suppressed when these conditions occur.
MJO STATE :MJO is in phase 2 and is of large enough amplitude so in the next few days shall enhance rainfall in Sri Lanka