Highlights: Drought conditions were seen throughout the country with only less than 10 mm/day rainfall received mostly by the south-western region of the country. WRF, CFS and GFS rainfall prediction models predict high rainfall after the 15th October. High rainfall (up to 125 mm) is expected in south-western, western and eastern regions of the country. During 12th- 17th very heavy rainfall is expected close to Pottuvil. The tropical pacific SST anomaly is close to -0.5 OC (weak La Niña threshold). A La Niña in October- November period usually results in very dry weather in Sri Lanka. MJO shall be in the western-Pacific during the next 15 days and shall suppress rainfall in Sri Lanka.
Weekly Monitoring:On 5th of October up to 20 mm rainfall was observed in surrounding areas of Balangoda and Horana. On the same day coastal areas of Galle received up to 20 mm rainfall while adjacent southern sea received rainfall up to 30 mm. On 6th north eastern sea near the island received up to 20 mm rainfall. No rainfall was recorded in any part of the island on 7th. On 8th surrounding areas of Kalupahana, the meeting point of Nuwara Eliya, Ratnapura and Badulla district borders received up to 20 mm rainfall. Also several areas in Colombo, Kalutara, Galle, Matara and nearby southern sea received up to 10 mm rainfall. No significant rainfall was observed during the period 9th - 11th. For the past week, the RFE 2.0 tool shows rainfall up to 25 mm for Matugama, Kalawana, Madampe, Mahiyangana areas and for the southern sea near the island. Up to 10 mm rainfall is shown for Trincomalee and Batticaloa including the adjacent sea regions. A below average rainfall of 10-25 mm is shown for Kilinochchi, Mullaitivu, Jaffna, Batticaloa, Ampara and Matara districts. For the rest of the country a below average rainfall of 25-50 mm is shown except for Gampaha region where a below average rainfall between 50-100 mm is shown.
Monthly Monitoring: Below average rainfall conditions were experienced in the entire island in the month of September. Monthly average amount to 120 mm/month in Ahungalla and Ratnapura town while everywhere else the rainfall did not exceed 60 mm/month. The CPC Unified Precipitation Analysis tool shows ~75 mm of total rainfall in Ratnapura, ~25 mm of rainfall in Colombo, Kegalla, Nuwara Eliya, Bandarawela and Matara areas.
During the period from October 2nd–8th the lowest temperature of 15-20 OC was recorded in Nuwara Eliya. The maximum temperature to be recorded was between 35-40 OCOC in the north eastern coastal belt. The maximum temperature of Kandy, Kegalla and Badulla areas was 25-30OC.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 by Kandy, Kegalla, Ratnapura, Badulla districts and the coastal region of Mannar district. The rest of the island experienced an above average temperature of 0-3OC .
At 850 mb level up to 30 km/h north westerly wind was experienced by the entire island except for the Northern province which experienced wind in the same direction with speed less than 20km/h. At 700 mb level southern regions of the island experienced north westerly winds with speed up to 20 km/h while northern and central regions experienced wind with speed less than 18 km/h in the same direction.
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 O below average sea surface temperature was observed in the western sea of Sri Lanka.
14-day prediction: NOAA NCEP models predicts total rainfall between 35-45 mm in Galle, Matara districts including the adjacent sea regions during 12th-18th October. For the same period total rainfall between 25-35 mm is expected for Ratnapura district and the area along the district border of Hambantota and Monaragala. For the period 19th-25th October total rainfall between 65-75 mm is expected in Galle and Matara districts with adjacent sea expected to receive 75-85 mm total rainfall. Kalutara, Ratnapura, Hambegamuwa and Yala areas are expected to receive total rainfall between 45-55 mm while Colombo, Avissawella, Nuwara Eliya, Bandarawela and Monaragala areas expected to receive total rainfall between 35-45 mm. A total rainfall between 25-35 mm is expected for Gampaha, Kegalla, Kandy, Badulla and Ampara regions.
Weekly prediction: IMD GFS model predicts rainfall between 20-40 mm in surrounding areas of Mullaitivu and adjacent sea area on 13th of October. Rainfall between 10-20 mm is expected for rest of the Northern province and North Central province including several areas of Trincomalee, Ratnapura, Kalurara and Galle districts. During 14th and 15th Western and Eastern sea regions near the island are expected to receive rainfall between 40-70 mm. On 14th coastal regions of Trincomalee, Gampaha, Colombo, Kalutara are expected to receive rainfall between 20-40 mm with rest of the island expected to receive rainfall between 10-20 mm except for Kurunegala and Hambantota areas. Western and Eastern sea regions near the island are expected to receive rainfall between 40-70 mm. Rainfall between 20-40 mm is expected in Batticaloa, Trincomalee, Polonnaruwa and Bibile areas on 15th with rest of the country expected to receive rainfall between 10-20 mm. On 16th Ampara district is expected to receive rainfall between 20-40 mm with adjacent sea receiving rainfall between 40-70 mm. Rest of the island except for Kilinochchi and Jaffna districts is expected receive up to 10-20 mm rainfall. On 17th south eastern sea near the island is expected to receive rainfall between 40-70 mm with most of the island except for Jaffna, Kilinochchi, Mannar, Kurunegala, Kegalla, Kandy and Hambantota areas expected to receive rainfall between 10-20 mm. On 18th the western and south eastern sea near the island is expected to receive rainfall between 40-70 mm. The whole island except for Kurunegala is expected to receive rainfall between 10-20 mm. On 19th the rainfall is expected to be increased with western sea receiving rainfall between 70-130 mm and also eastern sea receiving rainfall between 20-40 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 including coastal regions of Puttalam and Galle on 14th. Several other eastern and western coastal and central regions of the country is expected to receive up to 10 mm rainfall. On 15th the rainfall is expected to be increased with surrounding areas of Kalutara and Trincomalee areas and eastern sea near the island receiving rainfall up to 124 mm. Colombo and Kegalla areas are expected to receive rainfall up to 65 mm.
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 OC maximum temperature in Monaragala. The maximum temperature along the coastal belt in the Northern and Eastern sides of the country and in Vavuniya, Mannar, Polonnaruwa, Anuradhapura and Badulla districts will be between 35-40 OC. The maximum temperature of Ratnapura area will be between 25-30 OC while in Kandy, Matale, Puttalam, 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 30 km/h north westerly wind in the Southern province. Up to 18 km/h westerly wind is expected for the central part of the country with northern region expected to receive northerly wind with speed less than 15 km/h. The 700 mb level predicts up to 18 km/h north westerly wind for the southern half of the country while rest of the island is expected to receive wind with speed less than 10 km/h in the same direction.
MJO based OLR predictions
MJO shall suppress the rainfall in Sri Lanka in the next 15 days.