Highlights: Dry weather persisted in the country during 13th- 19th July and therefore the average rainfall deficit in the country has increased up to 60 mm. Heavy rainfall was only seen in Kantale/ Aralaganvila and Badulla areas. Above average rainfall was only received in Badulla region. Extreme rainfall was seen in the sea off the coast of Arugambay. Highest temperature was reported in the eastern side of the country while minimum temperature as usual was reported in Nuwara Eliya region. Reduced wind speed (only up to 20 km/h) was seen at the 700 mb level while up to 55 km/h wind was seen at the 850 mb level. NOAA NCEP and IRI CFS models does not expect much rainfall in the next two weeks but IMD WRF and GFS models predict heavy rainfall in Western and South-western regions in the next week. MJO is also expected to be present in the Indian ocean region which shall enhance rainfall condition in the country.
Weekly Monitoring:No rainfall was received by the entire island on the 13th. On the 14th Up to 50 mm rain was received by Bibile area and the surrounding areas received up to 40 mm rainfall. The entire country except the Northern province received up to 10 mm rainfall on the 15th while up to 40 mm rain was seen around Aralaganvila area. Light rainfall (up to 5 mm) continued in the entire country on the 16th as well. On the 17th Eastern and Central regions received rainfall. Heavy rainfall up to 40 mm was seen close to Badulla area while up to 90 mm Extremely heavy rainfall was seen in the sea off the coast of Arugambay. Rainfall ceased in the entire country on the 18th. Heavy rainfall (Up to 20 mm) was received by Kantale area on the 19th. During the week 13th- 19th July, rainfall received by the Western and South-western regions of the country was up to 50 mm below average. Above average rainfall was only received by Badulla region which was up to 50 mm.
Monthly Monitoring: Rainfall for the month of June was very low and below the historical average compared to the excessive rainfall in the previous month. The monthly average does not exceed 8mm in the entire island. Rainfall was mostly in the south western region of the country which totaled up to 75- 100 mm in the entire month. This amounts to only 50-80% of the usual rainfall for the month of June. Remaining part of the country received only 25-50% of the normal rainfall. With this, the average rainfall deficit in the entire country which was at 50 mm in the previous week had increased to 60 mm by this week (19th July).
During the week from 10th – 16th July, the highest temperature of 35-40 0C was recorded in the eastern side of the island. The lowest temperature of 15-20 0C was recorded in Nuwara Eliya. For the period, the temperature was 1-3 0C above average in the whole country except around Nuwara Eliya which was cooler.
Up to 55 km/h wind was seen in the entire country at the 850 mb level. The wind speed at the higher 700 mb level dropped to around 20 km/h in the previous week.
Pacific seas state: July 13, 2016
During early July 2016 the tropical Pacific SST anomaly was slightly below zero, indicating ENSO-neutral conditions. The key atmospheric variables also indicate neutral ENSO conditions. This includes near-average upper and lower level tropical Pacific winds, as well as mainly near-normal cloudiness and rainfall patterns in the central and eastern equatorial Pacific. Most ENSO prediction models indicate neutral ENSO conditions during July, with likely development of La Niña (most likely weak) by late August or September, lasting through fall and into winter. (Text Courtesy IRI)
Indian Ocean State
Neutral SST anomaly was observed around Sri Lanka.
14-day prediction: NOAA NCEP models predict up to 35 mm total rainfall in the South-western region of the country during 20th- 26th July. There shall not any rainfall during 27th July- 2nd August in any part of the country.
Weekly prediction: IMD GFS model predicts 20 – 40 mm rain close to Chilaw on the 22nd and the 23rd. On the 24th, there shall be 40- 70 mm rain in the coastal region from Chilaw to Kalutara. Up to 130 mm rain is expected in the South-western sea on the 25th and up to 40 mm rain on the 26th in the same area. Less than 20 mm rain expected in the entire country on the 27th.
IMD WRF Model Forecast & IRI forecast:According to the IMD WRF model, up to 124 mm of rainfall is expected in Ratnapura and Batticaloa areas and up to 65 mm of rainfall is expected in the surrounding areas on the 22nd July. Similar rainfall pattern is expected on the 23rd as well but the maximum rainfall shall be around 65 mm. During 20th- 25th July no extreme rainfall is expected in the country.
Seasonal Prediction:As per IRI Multi Model Probability Forecast for July to September, the total 3-month precipitation shall be climatological. The 3-month temperature has more than 70-80% likelihood in the entire country of being in the above-normal tercile during this period.
NOAA CPC GFS model predicts 35-40 0C maximum temperature along the coastal belt in the Eastern side of the country. Maximum temperature in Kurunegala, Kandy, Colombo and Matara areas will be 30-35 0C. For the same week maximum temperature of Kalutara, Galle and Ratnapura areas will be 25-30 0C. During the same week, minimum temperature is expected around Nuwara Eliya to be 15- 20 0C. The minimum temperature of Jaffna will be 25-30 0C and that of rest of the country will be 20-25 0C.
AAt 850 mb level, up to 55 km/h westerly and north westerly wind is expected in lower half of the country while up to 40 km/h westerly wind is expected in northern half of the country. At 700 mb level up to 30 km/h westerly wind is expected in southern regions and up to 20 km/h wind expected in northern regions.
MJO based OLR predictions
MJO shall be in the Indian Ocean region in the next 15 days and therefore it shall enhance rainfall in Sri Lanka.