Highlights: During the previous week, wet weather conditions were experienced by Jaffna and Kilinochchi districts of the country. On 26th up to 35 mm of rainfall was recorded in Jaffna. As expected, the lowest temperature was recorded in Nuwara Eliya to be between 15- 20 0C. The maximum temperature of between 35-4O 0C was recorded in the northern and eastern coastal belt. Up to 55 km/h north westerly wind was experienced by the Southern and Central regions of the country. No extreme weather conditions were experienced by the country in the month of August. Wet weather conditions are expected in the Northern Province in the week from 1st-7th September. Up to 55 km/h north westerly wind is expected in the southern region of the country including North Western and Uva provinces.
Weekly Monitoring:On 24th up to 20 mm of rainfall was recorded in the border of Ampara and Moneragala close to Ellegoda while up to 15 mm of rainfall was recorded in the surrounding areas and the northern region of Ampara, Badulla and Moneragala districts. Mostly dry weather conditions were experienced on 25th with only slight rainfall of less than 10 mm in a few areas. On 26th up to 35 mm of rainfall was recorded in Jaffna, Karaitivu and close by areas, while the rest of Jaffna district received up to 15 mm. On 27th up to 15 mm of rainfall was recorded in the Jaffna district and the adjacent sea. On 28th between 10-15 mm of rainfall was recorded in Mannar, Kilinochchi, Mulalitivu, Vavuniya and Trincomalee districts. On 30th up to 15 mm of rainfall was recorded in the border of Moneragala and Ampara close to Lahugala. For the past week, the RFE 2.0 tool shows rainfall between 25-50 mm in Galle and Matara districts and in some other regions surrounding Ratnapura, Mannar, Vavuniya, Trincomalee Nuwara Eliya and Monaragala. Similar amount of rainfall is shown near the border of Ampara, Badulla and Monaragala districts. A rainfall between 10-25 mm is shown in some areas of Kegalle, Hambantota, Badulla and Matale districts. An above average rainfall of 25-50 mm is shown in Karampan and Karainagar of Jaffna district. 10-25 mm above average rainfall can be seen in Mullaitivu and Kilinochchi districts and in Trincomalee. It also shows a below average rainfall of 25-50 mm in the Colombo district and in nearby Gampaha, Kalutara, Avissawella and Horana areas. A below average rainfall of 10-25 mm can be seen in the central and western regions of the island including Polonnaruwa, Ampara and Galle regions.
Monthly Monitoring: Average rainfall conditions were experienced in the month of August. The CPC Unified Precipitation analysis tool shows ~50 mm of total rainfall in Galle, Matara and Jaffna districts. The RFE 2.0 tool shows ~75 mm of total rainfall in the Jaffna district, northern region of Uva province including Radaliyadda, Beligalla and Arawa areas, ~ 50 mm of rainfall in rest of Badulla, Nuwara eliya, Kilinochchi, Trincomalee districts and Kuruwita, Ratnapura and Palmadulla areas.
For the period from 21th-27th 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, Kegalle, Ratanapura, Badulla and Galle areas was 25-30 0C. The maximum temperature of rest of the country was between 30-35 0C. During this period an above average temperature of 0-1 0C was observed in the northern and central regions of the country including Galle 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 including Anuradhapura, Polonnaruwa, and Trincomalee experienced 30-35 km/h wind in the same direction. At 700 mb the entire country experienced north westerly wind with 30-35 km/h speed.
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 between 35-45 mm of rainfall in the Jaffna Sea few kilometers away from the island for the period from 31st August – 6th September. For the same period up to 35 mm of rainfall are expected in Jaffna and Kilinochchi districts and the adjacent sea while up to 25 mm of rainfall is expected in Mullaitivu and Vavuniya districts and the Adampane, Pulmudai and surrounding areas. Slightly enhanced rainfall conditions are expected in the Northern region of the island for the period from 7th-13th September. During that period up to 75 mm of rainfall is expected in the Jaffna district and the adjacent sea, up to 65 mm of rainfall is expected in Kilinochchi district and the adjacent sea and up to 55 mm of rainfall is expected in the Mullaitivu district and the northern region of Mannar district. For the same period between 35- 45 mm of rainfall is predicted in Vavuniya and the southern region of Mannar district and between 15-35 mm of rainfall is predicted in Anuradhapura and Trincomalee districts and the surrounding areas.
Weekly prediction: IMD GFS model predicts no rainfall all over the country except on 1st and 2nd. On 1st between 20-40 mm of rainfall is expected close to Kahawa, Ahungalla, Bentota and the adjacent sea while up to 20 mm of rainfall is expected in rest of the Galle district, Kalutara and Colombo districts and the adjacent sea. On 2nd rainfall is expected to be decreased and between 10-20 mm of rainfall is expected in the western province and the adjacent sea. On 2nd, 4th-6th period, between 10-20 mm of rainfall is expected in the Jaffna sea.
IMD WRF Model Forecast & IRI forecast:According to the IMD WRF model, for the period from 31st August-2nd September up to 36 mm of total rainfall is expected in the Western province, North Western province, Galle and Kegalle districts. The model does not predict considerable rainfall on the 3rd. The IRI model predicts no extreme conditions for the coming week.
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 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, Mannar 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 North Western, Central and Uva provinces while up to 36 km/h south westerly wind is expected in the northern and eastern regions of the country. The 700 mb level predicts westerly winds for the entire island with speeds less than 30 km/h.
MJO based OLR predictions
MJO will be weak over the next seven days but will suppress the rainfall conditions over Sri Lanka.