Highlights: During the previous week from 18th-24th August, slightly wet weather conditions were expected in certain areas of the country. On 24th 78.5 mm of rainfall was recorded from Jaffna. Lowest temperature was recorded in Nuwara Eliya to be between 15-20 0C while the maximum temperature was recorded from the eastern coastal belt to be between 35-40 0C. 1-3 0C above average temperature anomaly was experienced throughout the country except in Nuwara Eliya. Up to 55 km/h north westerly wind was experienced in the lower half of the country including Kurunegala district. Considerably wet weather conditions are expected in Kalutara and Galle areas for the week from 25th-31st August. Up to 70 mm of rainfall is expected close to Beruwala and Bentota for the period from 25-28th. Up to 40 mm of rainfall is expected in surrounding areas from 25th-31st August. Up to 55 km/h north westerly wind is expected in Western, Sabaragamuwa, Southern and Uva provinces.
Weekly Monitoring:For the past week, the RFE 2.0 tool shows rainfall between 10-25 mm in the Central province and in some other regions surrounding Kurunegala, Polonnaruwa, Trincomalee, Ampara, Badulla, Monaragala, Ratnapura and Kegalle. It also shows a below average rainfall in most parts of the island. A below average rainfall of 25-50 mm is shown in the Colombo district and the bordering regions of Mannar, Vavuniya and Mullativu districts. A similar anomaly in rainfall is shown for Hasalaka and Hettipola areas.
Monthly Monitoring: Rainfall for the month of July was considerably high compared to the month of June. However the average rainfall did not exceed 8 mm in any of the districts. The rainfall of northern and central regions of the country was slightly above normal with a values of between 2-6 mm while that of the western and southern regions were 3-5 mm below normal.
For the period from 14th-20th August the lowest temperature of 15-20 0C was recorded in Nuwara Eliya. The maximum temperature to be recorded was between 35-40 0C in the North and Eastern coastal belt. The maximum temperature of Kandy, Colombo, Kurunegala and Matara areas were 30-35 0C. During this period an above average temperature of 0-1 0C was observed in Nuwara Eliya while in rest of the island the temperature was 1-3 0C above average.
At 850 mb level 35-55 km/h north westerly wind was experienced by the central and southern regions of the country while the northern region experienced 30-35 km/h wind in the same direction. At 700 mb level south western region of the country experienced north westerly wind with 30-35 km/h speed while rest of the country experienced wind in the same direction with speed less than 30 km/h.
Pacific seas state: August 18, 2016
During mid-August 2016 the tropical Pacific SST anomaly was close to -0.5C, approaching the weak La Niña threshold. However, most key atmospheric variables continue to indicate neutral ENSO conditions. Although the upper level winds in the tropical Pacific are slightly suggestive of La Niña, the lower level winds remain near average. The Southern Oscillation index and the pattern of cloudiness and rainfall in the equatorial Pacific also indicate neutral ENSO despite a mild tilt toward La Niña. The collection of ENSO prediction models indicate SSTs most likely near the borderline of cool-neutral and weak La Niña from the present through fall and into winter. (Text Courtesy IRI)
Indian Ocean State
0.5 0C above average sea surface temperature was observed in the north eastern sea of Sri Lanka..
14-day prediction: NOAA NCEP models predicts 75-85 mm of total rainfall close to Matara and Weligama areas during 24th-30th August. During the same period up to 75 mm of rainfall is expected in the rest of Matara district and up to 55 mm of rainfall is expected in Jaffna, Kilinochchi, Sella Kataragama, Tanamalwila, Kalawana and surrounding areas. For the period from 31st August-6th September up to 45 mm of rainfall is expected in Jaffna, Matara and the adjacent sea and up to 35 mm of rainfall is expected in Wiraketiya, Walasmulla areas in Hambantota district and Pallebedda and Moragoda areas in Ratnapura district.
Weekly prediction: IMD GFS model predicts wet weather conditions in Kalutara and Galle areas in the week from 25th-31st August. On 25th 40-70 mm of rainfall is expected in the coastal areas of Kalutara and Galle districts including Kalutara town, Bentota, Beruwala and Hikkaduwa and the adjacent sea and also in the sea close to Dehiwala and Colombo. On the same day rest of the western province, western sea, Matara district and the adjacent sea may experience 20-40 mm of rainfall. On 26th Galle district and adjacent sea, Beruwala and Alutgama areas may experience 40-70 mm of rainfall, the rest of the Western Province, Western sea, Matara district and the adjacent sea may experience 20-40 mm of rainfall. On 27th, 40-70 mm of rainfall is expected in Galle district and 20-40 mm of rainfall is expected in Matara district, Western Province, Puttalam and Kurunegala districts, Western, Southern and the North Western sea. 40-70 mm of rainfall is expected close to Beruwala, Bentota and Balapitiya areas on 28th. On the same day Colombo, Kalutara and rest of the Galle district, Western and Southern sea may experience 20-40 mm of rainfall. The intensity of the rainfall is expected to be decreased on 29th. On that day 20-40 mm of rainfall is expected in Kalutara and Galle districts and the adjacent sea while the surrounding areas, Colombo and the Southern sea shall experience up to 20 mm of rainfall. On 30th Colombo, Kalutara, Galle. Matara areas and the adjacent sea may experience 20-40 mm of rainfall, Puttalam, Gampaha, Kegalle, Ratnapura districts, Walasmulla, Tangalle and the southern sea may experience 10-20 mm of rainfall. On 31st the coastal areas of the Western Province, Western sea, Galle and the Matara districts and the adjacent sea may experience 20-40 mm of rainfall, the rest of the Western province, Gampaha, Southern part of Puttalam district and the Southern sea may experience 10-20 mm of rainfall.
IMD WRF Model Forecast & IRI forecast:According to the IMD WRF model up to 124 mm of rainfall is expected in Galle district for the period from 24th-26th August. For the same period up to 64 mm of rainfall is expected in Kalutara and Matara districts and close to Kahawatta and Madampe areas in Ratnapura district and up to 35 mm of rainfall is expected in Colombo, Gampaha, Puttalam, Kurunegala, Kegalle and Ratnapura districts. For the period from 24th-29th, the IRI model predicts very heavy rainfall conditions close to Horana, Matugama, Balapitiya, Ambalangoda, Hikkaduwa areas and heavy rainfall conditions in the surrounding areas including Moragala, Agalawatta, Pelawatta, Elpitiya and Boossa.
Seasonal Prediction:As per IRI Multi Model Probability Forecast for September to November, 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 and in Mullaitivu, Polonnaruwa and Monaragala districts. The maximum temperature of Gampaha, Colombo, Kalutara, Galle, Ratnapura and Kegalle areas will be between 25-30 0C while in Kandy, Matale, Puttalam, Kurunegala, Anuradhapura and Matara districts the temperature will be between 30-35 0C. For the same period minimum temperature is expected in Nuwara Eliya to be between 15-20 0C.
The 850 mb level predicts up to 55 km/h north westerly wind in the southern part of the country including Kurunegala, Kandy, Badulla and Moneragala areas while up to 36 km/h south westerly wind is expected in the central region of the country and also in Ampara and Puttalam areas. The 700 mb level predicts up to 36 km/h south westerly and westerly winds in the entire island except for Northern Province.
MJO based OLR predictions
MJO will be in the Western Pacific Ocean in the next seven days and shall suppress the rainfall conditions in Sri Lanka.