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Friday, September 23, 2016

Weekly Hydro-meteorological Report, 22, September 2016

Highlights: Mixed weather conditions were experienced in the previous week from 14th-20th September in the island. Eastern sea near the island received heavy rainfall on 15th with sea region near Batticaloa receiving up to 180 mm. The highest rainfall of 30 mm for the period was recorded close to Beligalla and Padiyathalawa near the Badulla Ampara district border. The minimum temperature of 20 OC was recorded from Nuwara Eliya district while the maximum temperature was recorded from the North Eastern coastal areas to be between 35-40 OC. Up to 35 km/h north westerly winds were recorded in the entire country. For the period from 22th-27th 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. In the central regions up to 55 km/h westerly wind is expected.
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Weekly Monitoring:On 14th up to 10 mm rainfall was observed in the nearby sea region of Trincomalee. On 15th heavy rainfall was observed in the eastern sea region near the island with sea nearby Batticaloa receiving up to 180 mm rainfall. Mutur and Trikonamadu region near the Batticaloa and Polonnaruwa district border received up to 20 mm rainfall. On 16th Punkudutivu, Karampan and Eluvitivu of Jaffna district received up to 10 mm rainfall. On 17th Weddagala area in the Ratnapura district received up to 10 mm rainfall. Rainfall up to 20 mm was observed in the surrounding areas of Hasalaka, Madugoda, Andaulpota, Hembarawa, Kanawegolla, Kehelula and Maha Oya on 18th. Neighboring regions of Beligalla and Batalayaya of Badulla district and Padiyathalawa and Ellegoda of Ampara district recived up to 30 mm rainfall. For the past week, the RFE 2.0 tool shows rainfall up to 5 mm for the most parts of the country with between 10-25 mm in surrounding areas of Batticaloa and Welikanda. The same amount of rainfall is also shown for Ampara, Maha Oya, Beligalla and Bibile areas of Uva and Northern provinces and Weddagala of Ratnapura district. A below average rainfall of 25-50 mm is shown for the Colombo district and adjacent areas of Gampaha and Kalutara districts. A below average rainfall of 10-25 mm is shown for the rest of the Western Province and Galle, Matara, Kegalla, Nuwara Eliya and Kandy districts including several areas of Kurunegala, Matale, Badulla and Hambantota districts.

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 11th-17th September the lowest temperature of 15-20 OC was recorded in Nuwara Eliya. The maximum temperature to be recorded was between 35-40 OC in the North eastern coastal belt. The maximum temperature of Kandy, Kegalle, Ratanapura 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 0-1 OC was observed in Monaragala, Hambantota, Ampara, Gampaha and Kegalla districts including the North Western province. The temperature was 0-1 OC above average in the rest of the island.
At 850 mb level 20-35 km/h north westerly wind was experienced by the entire island. At 700 mb Jaffna and Kilinochchi districts 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.

Ocean State
Pacific seas state: September 15, 2016
During mid-September 2016 the tropical Pacific SST anomaly was close to -0.5C, the weak La Niña threshold. However, not all of the atmospheric variables support weak La Niña conditions. Although the upper level winds in the tropical Pacific are somewhat 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 are somewhat suggestive of weak La Niña conditions, but could also be interpreted as being in the cool-neutral range. The collection of ENSO prediction models indicates SSTs hovering at levels near borderline La Niña during fall, then weakening to cool-neutral in late fall and into winter.(Text Courtesy IRI)

Indian Ocean State
0.5 OC below average sea surface temperature was observed in the western sea of Sri Lanka


14-day prediction: NOAA NCEP models predicts no rainfall in the entire island until 27th September. For the period 28th September to 4th October between 15-25 mm rainfall is expected for Jaffna and Kilinochchi districts while up to 15 mm rain is expected for Mullaitivu, Vavuniya and Mannar districts and the northern region of Anuradhapura district.

Weekly predictionIMD GFS model predicts dry weather conditions for the most parts of the island in the period from 22nd-28th September. South western region of the island and the adjacent sea area is expected to revive up to 10 mm rainfall on each day during this period. In addition, on 23rd,24th and 28th the surrounding areas of Mullaitivu and nearby north eastern sea area are also expected to receive rainfall up to 10 mm.

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 21st-23rd. During the same period less than 8 mm of rainfall is expected in rest of the North Western province, Matara and Ampara areas. On the 24th the rainfall that persisted in the Western province is shown to be expanded to Kurunegala and Kandy districts and the adjacent sea areas of the Western province. The IRI model predicts no extreme weather conditions for the period from 21st-24th.

 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 Anuradhapura, Polonnaruwa and Monaragala districts will be between 35-40 0C. The maximum temperature of Colombo, Kalutara and Ratnapura areas will be between 25-30 OC while in Kandy, Matale, Puttalam, Kurunegala, Galle and Matara districts the maximum temperature will be between 30-35 OC. For the same period minimum temperature is expected in Nuwara Eliya to be between 15-20 OC.

The 850 mb level predicts up to 54 km/h north westerly wind in the southern region of the country. Westerly wind with the same speed is expected in the central region including North Western province. Up to 36 km/h north westerly and westerly wind is expected for the northern region of the island including the southern part of Ampara district. The 700 mb level predicts up to 54 km/h north westerly wind in the southern and western regions of the country including Nuwara Eliya and Kandy districts. Up to 36 km/h wind in the same direction is expected for the rest of the island.

MJO based OLR predictions
MJO shall suppress the rainfall in Sri Lanka in next 15 days.

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