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Thursday, September 15, 2016

Weekly Hydro-meteorological Report, 15, September 2016

Highlights: Mixed weather conditions were experienced in the previous week from 6th-12th September. Up to 10 mm of rainfall was recorded from the Eastern sea and several areas in the eastern side of the country during the first few days of the week. The highest rainfall for the period was recorded close to Walasmulla near the Matara Hambantota border. The minimum temperature of 20 OC was recorded from Nuwara Eliya district while the maximum temperature was recorded from the North Eastern and Eastern coastal areas to be between 35-40 OC. Up to 55 km/h north westerly winds were recorded in the Southern areas of the country. For the period from 14th-20th the NOAA NCEP model predicts dry weather conditions in the island. Up to 55 km/h north westerly wind is expected in the southern half of the country including the north western province. In Matale and Kurungela areas up to 55 km/h south westerly wind is expected.
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Weekly Monitoring:On 7th of September North Eastern sea near Mullaitivu received rainfall up to 15 mm while Chundikulam and Vettilakenni of Jaffna district received up to 10 mm rainfall. A rainfall up to 5 mm was observed in surrounding areas of Chunnavil, Monniyakulam and Kokkavil. No significant rainfall was observed during the period 8th – 9th. On 10th coastal regions Gampaha, Colombo and Matara districts and nearby sea received up to 5 mm rainfall. Neighboring regions of Ambalangoda, Boossa, Unawatuna, Ahangama and Baddegama of Galle district received rainfall up to 10 mm. On 12th Ratnapura received up to 15 mm rainfall. For the past week, the RFE 2.0 tool shows rainfall between 10-25 mm in surrounding areas of Ratnapura. A below average rainfall of 25-50 mm is shown for the provinces Western and Sabaragamuwa and districts Galle, Nuwara Eliya, Kandy and Badulla. A below average rainfall of 10-25 mm is shown for the rest of the island except for the Northern Province.

Monthly Monitoring: Below average rainfall conditions were experienced in the entire island in the month of August except in Jaffna. Monthly average amount to 7 mm/day in Jaffna peninsula and Ratnapura town while everywhere else the rainfall did not exceed 5 mm/day. The CPC Unified Precipitation Analysis tool shows ~75 mm of total rainfall in Jaffna, ~50 mm of rainfall in Kilinochchi, Ratnapura and Matara areas.

For the period from 4th-10th September the lowest temperature of 10-15 OC was recorded in Nuwara Eliya. The maximum temperature to be recorded was between 35-40 OC in the North and Eastern coastal belt. The maximum temperature of Kandy, Kegalle, Ratanapura, Badulla and Galle areas was 25-30 OC. The maximum temperature of rest of the country was between 30-35 OC. During this period an above average temperature of 0-3 OC was observed in Colombo and Ampara while in rest of the island the temperature was 0-1 OC above average.
At 850 mb level 35-55 km/h north westerly wind was experienced by the southern regions of the country while Central region including the North Central province 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.

Ocean State
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 OC below average sea surface temperature was observed in the eastern and southern sea of Sri Lanka.


14-day prediction: NOAA NCEP models predicts no rainfall in the entire island until 27th September except in Jaffna peninsula where up to 15 mm rain expected in each week.

Weekly predictionIMD GFS model predicts dry weather conditions in the period from 15th-21st September. No rainfall is predicted in the entire country except on the 15th. On that day between 10-20 mm of rainfall is predicted in the western province, Galle district and adjacent sea, in the eastern sea close to Trincomalee as well as in the northern sea close to Jaffna peninsula.

IMD WRF Model Forecast & IRI forecast:According to the IMD WRF model up to 35 mm of rainfall is expected in the western province, Kegalle,, Ratnapura, Galle and Chilaw areas during the period from 14th-16th. During the same period less than 8 mm of rainfall is expected in rest of the north western province, Matara and Moneragala areas. On the 17th the rainfall that persisted in the Western province is shown to be constricted to Kalutara and Colombo districts and coastal areas in southern part of Puttalam district. The IRI model predicts no extreme weather conditions for the period from 14th-19th.

 Seasonal Prediction:As per IRI Multi Model Probability Forecast for October to December, the total 3-month precipitation shall be climatological in the northern half of the island. However the southern half of the island has 30-40% likelihood of being in the below-normal tercile. 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 40-45 OC maximum temperature in the areas along the border of Eastern and Uva provinces. The maximum temperature along the coastal belt in the Eastern side of the country and in Polonnaruwa and Monaragala districts will be between 35-40 OC. The maximum temperature of Colombo, Kalutara, Galle and Ratnapura areas will be between 25-30 OC while in Kandy, Matale, Puttalam, Kurunegala and Matara districts the maximum temperature will be between 30-35 OC. For the same period minimum temperature is expected in Nuwara Eliya, Kandy and Badulla to be between 15-20 OC.

The 850 mb level predicts up to 54 km/h north westerly wind in the western, central and southern regions of the country. Up to 36 km/h south westerly wind is expected for North Central province and Mannar district. The 700 mb level predicts up to 54 km/h westerly wind in the western regions of the country including North Central and Central provinces. Up to 36 km/h wind in the same direction is expected for the rest of the island.

MJO based OLR predictions
MJO will be in the Indian Ocean in the next seven days and will enhance the rainfall conditions over Sri Lanka.

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