Highlights: A slight increase of rain was experienced for the period from 10-16th August compared to the previous week. Up to 30 mm of rainfall was recorded close to Jaffna on 10th while rainfall between 10-20 mm was recorded in several parts of the island over the next few days. The lowest temperature was recorded in Nuwara Eliya to be between 15-20 OC while the maximum temperature was recorded in the eastern and northern coastal belt to be between 35-40 OC. Up to 55 km/h north westerly wind was recorded in the southern half of the country. For the week from 18th-24th August rainy weather is expected in the western province and the adjoining sea. On 19th up to 40 mm of rainfall is expected close to Kalutara and Beruwala while on 24th up to 40 mm of rainfall is expected in the Western province. Up to 55 km/h north westerly wind is expected in the southern half of the country.
Monitoring
Rainfall
Weekly Monitoring:On 10th of August sea near the Jaffna Peninsula received rainfall up to 30 mm. The surrounding areas near the Monaragala and Badulla district border including Bandarawela, Monaragala and Badulwewa received rainfall up to 10 mm. No significant rainfall was observed in the entire island during the period from 11th-13th August. On 14th rainfall up to 20 mm was observed in Avissawella, Deraniyagala and Kithulgala regions of Kegalla district and Watawela and Kotmale regions of Nuwara Eliya district. Dry weather conditions prevailed during 15th and 16th of August. For the past week, the RFE 2.0 tool shows rainfall in some regions of Kegalle and Nuwara Eliya districts where Ruwanwella, Avissawella, Kithulagala, Watawela, Kothmale and Nuwara Eliya received rainfall between 10-25 mm. It also shows below average rainfall of 25-50 mm in Kalutara and adjacent areas and below average rainfall of 10-25 mm in the rest of Western province, Galle and Matara districts of Southern province and some of the areas in Sabaragamuwa province. A similar anomaly is shown in the bordering regions of Badulla and Ampara districts and Polonnaruwa and Batticaloa districts.
Monthly Monitoring: Considering the dry weather condition that prevailed in the month of June, the rainfall for the month of July was comparatively high. The RFE 2.0 tool shows a total rainfall of ~150 mm close to Vavuniya and Ratnapura town, ~100 in several places of Badulla district and surrounding areas of Ratnapura town. It also shows ~75 mm of rainfall in central province, Badulla district, Kalutara, Galle, and Anuradhapura districts and the southern sea.
For the period from 7th-13th August the lowest temperature was recorded in Nuwara Eliya to be between 15-20 OC. The maximum temperature was recorded in the North and Eastern coastal belt to be between 35-40 OC. The maximum temperature of Kandy, Colombo, Kurunegala, Galle and Matara areas were 30-35 OC. During this period an above average temperature of 0-1 OC was observed in North Central and Eastern provinces while in rest of the island the temperature was 1-3 OC above average.
At 850 mb level 35-55 km/h north westerly wind was experienced by the southern half of the country while 30-35 km/h north westerly wind was experienced by the northern half including Matale, Kurunegala and Ampara districts. At 700 mb level north westerly wind was experienced all over the country with speed less than 20 km/h.
Ocean State
Pacific seas state: August 11, 2016
During early August 2016 the tropical Pacific SST anomaly was close to -0.5C, approaching the weak La Niña threshold. However, key atmospheric variables mainly continue to indicate neutral ENSO conditions. This includes near-average upper and lower level tropical Pacific winds and Southern Oscillation Index. The cloudiness and rainfall patterns in the equatorial Pacific also indicate neutral ENSO, but drier-than-average conditions near the dateline suggest a weak tendency toward La Niña. Most ENSO prediction models indicate cool-neutral conditions during August, with development of weak La Niña slightly favored for September/October, lasting through fall and into winter. (Text Courtesy IRI)
Indian Ocean State
0.5 OC above normal sea surface temperature was observed in the north eastern sea of Sri Lanka.
14-day prediction: NOAA NCEP models predicts 15-25 mm rainfall in the eastern side of Galle district including Yakkalamulla and Udugama areas, Moragala and Migahatenna areas close to Matugama for the period from 17-23rd August. During the same period up to 15 mm of rainfall is expected in Colombo, Ratnapura and Matara districts and the southern region of Kegalle district. For the period from 24th-30th August, between 45-55 mm of rainfall is expected in Matara district and adjacent sea, eastern side of Galle district, Jaffna district and the adjacent sea while between 35-45 mm of rainfall is expected in Kilinochchi, Mullaitivu, northern region of Trincomalee district including Pulmoddai, southern region of Ratnapura district and the eastern side of Hambantota district including Ganegoda. During the same period the rest of Ratnapura district, Colombo, Moneragala, Haputale, Mannar, Vavuniya and the rest of Trincomalee district may experience between 25-35 mm of rainfall while the rest of North Central province, Gampaha, Kegalle, Nuwara Eliya, Badulla and Ampara districts may receive up to 25 mm of rainfall.
Weekly prediction: IMD GFS model predicts rainy weather conditions in the western province for the week from 18th-24th August. On 18h up to 20 mm of rainfall is expected in Colombo and Gampaha districts, coastal areas of Kalutara district and the adjacent sea. On 19th 20-40 mm of rainfall is expected close to Kalutara and Beruwala and up to 20 mm of rainfall is expected in the rest of Western province, Galle and Matara districts and the adjacent sea. Up to 20 mm of rainfall is expected in western province, Galle district and the adjacent sea on 20th. On 21st the coastal areas of the Kalutara district and the adjacent sea, Trincomalee town and adjacent sea shall experience shall experience up to 20 mm of rainfall. Up to 40 mm of rainfall is expected in western sea close to Kalutara and Beruwala on 22nd. On the same day, the rest of the western province, Galle district and the rest of the western sea shall experience between 10-20 mm of rainfall. Between 20-40 mm of rainfall is expected close to Bentota on 23rd while the rest of western province, Galle district and western sea shall experience up to 20 mm of rainfall. The rainfall is expected to be intensified in 24th and up to 40 mm of rainfall is expected in Kalutara, Galle, southern region of Colombo and the western sea and between 10-20 mm of rainfall is expected in the surrounding areas.
IMD WRF Model Forecast & IRI forecast:According to the IMD WRF model, up to 65 mm of total rainfall is predicted close to Gampaha and up to 35 mm of rainfall is predicted in the rest of western province, Kurunegala, Galle and Kegalle districts for the period from 17-19th. From 17-20th, up to 65 mm of rainfall is predicted close to Horana.
Seasonal Prediction:As per IRI Multi Model Probability Forecast for August to October, 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.
Temperature
NOAA CPC GFS model predicts 35-40 OC maximum temperature along the coastal belt in the Eastern side of the country and in Kilinochchi, Mullaitivu, Polonnaruwa and Anuradhapura districts. The maximum temperature of Colombo, Kalutara, Galle and Kegalle areas will be between 25-30 OC while in Kandy, Matale, Puttalam, Kurunegala and Matara districts the temperature will be between 30-35 OC. For the same period minimum temperature is expected in Nuwara Eliya and Badulla to be between 15-20 OC.
Wind
The 850 mb level predicts up to 54 km/h north westerly wind in the southern part of the country including Kurunegala, Kandy and Moneragala areas while up to 36 km/h north westerly and westerly wind is expected in the central region of the country and also in Ampara and Batticaloa areas. The 700 mb level predicts up to 36 km/h north 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 rainfall in Sri Lanka.
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