Highlights: A significant increase in the rainfall events was observed during the previous week from 13th - 18th October compared to the previous week. The highest rainfall of 140 mm for the period was recorded in Kirinda area on 17th. The minimum temperature of 20OC was recorded from Nuwara Eliya district while the maximum temperature was recorded from the northern eastern and south eastern coastal areas to be between 35-40 OC. Up to 30 km/h north westerly winds were recorded in the southern regions of the country. For the period from 19th - 25th October the NOAA NCEP model predicts up to 45 mm rainfall for Galle and Matara districts. Up to 30 km/h north westerly wind is expected in the southern half of the country.
Monitoring
Rainfall
Weekly Monitoring:On 13th October Hasalaka and Madugoda areas of Kandy district received up to 20 mm rainfall. On 14th up to 90 mm rainfall was observed in Beligalla region of Badulla district while surrounding areas of Mahiyangana, Horabora Wewa and Alutketiyawa received up to 50 mm rainfall. Haputale and the rest of the northern half of Badulla district including Rangala, Hasalaka and Madugoda of Kandy district, Rambewa and Kahatagasdigiliya of Anuradhapura district received up to 40 mm rainfall. Up to 30 mm rainfall was observed in neighboring regions of Galagedara, Mawatagama, Kegalla, Mawanella, Gampola, Akurana, Kandy, Kundasale, Padiyathalawa, Maha Oya, Dehiattakandiya, Matale, Hettipola, Kalpitiya, Illavakulam, Anuradhapura, Kala Oya and Tirappane. Up to 20 mm rainfall was observed in most of the central regions of the island including several areas of North Central and North Western provinces. On 15th up to 50 mm rainfall was observed in Rambukkana area and in the western sea region adjacent to the island. Up to 30 mm rainfall was observed in surrounding areas of Udappuwa, Pallama Puttalam district, Giriulla, Polgahawela, Narammala of Kurunegala district, Ranwala, Mawanella of Kegalla district, Murutalawa, Katugastota of Kandy district and coastal area of Negombo region. Up to 20 mm was observed in several areas of Puttalam, Kurunegala, Anuradhapura, Kurunegala, Gampaha, Kegalla, Kandy, Nuwara Eliya, Colombo, Kalutara and Galle districts. On 16th south eastern sea near the island received up to 20 mm rainfall. On 17th up to 140 mm rainfall was observed in Kirinda area of Matara district and in south western sea near the island. Deniyaya and Hakmana regions received up to 120 mm rainfall while rest of the Matara district received up to 90 mm rainfall including Nelluwa, Embilipitiya, Middeniya areas. Up to 60 mm rainfall was observed in Rakwana of Kegalla district.Up to 50 mm rainfall was observed in Galle town, Hiniduma, Udugama areas of Galle district, Peliyagoda of Colombo district and Wiraketiya and Nonagama areas of Hambantota district. Rest of the Galle district received up to 40 mm rainfall except for Pitigala area where up to 30 mm rainfall was observed. Similar amount of rainfall was observed in Dehiwala, Aluthgama, Migahathenna, Kalawana, Madampe and Hambegamuwa. Up to 20 mm rainfall was observed inseveral areas of Colombo, Kalutara, Kegalla, Ratnapura, Monaragala and Hambantota districts. For the past week, the RFE 2.0 tool shows rainfall up to 100 mm for the surrounding areas of Haslaka and Mahiyangana areas along the district border of Galle and Matara. Up to 75 mm rainfall is shown for Galle district including the coastal areas of Western province, southern region of Ratnapura district and western region of Hambantota district. Rainfall between 10-25 mm is shown in several areas of Nuwara Eliya, Monaragala, Ampara, Polonnaruwa, Anuradhapura, Kurunegala and Puttalam. It also shows an above average rainfall of 25-50 mm in Matara district. A below average rainfall of 50-100 mm is shown for Mannar, Vavuniya, Anuuradhapura, Battcaloa, Polonnaruwa, Madampe and Nuwara Eliya regions. A below average rainfall of 25-50 mm for the most of the island.
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 9th–15th 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 and south eastern coastal belt. The maximum temperature of Kandy, Kegalla, 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 by the entire country except for the north eastern coastal belt where an above average temperature of 3-5OC was observed..
At 850 mb level up to 30 km/h north westerly wind was experienced by the southern region of the island. The rest of the country experienced wind in the same direction with speed less than 18 km/h. At 700 mb level southern regions of the island including Ampara district experienced north westerly winds with speed up to 20 km/h while rest of the country experienced wind with speed less than 18 km/h in the same direction
Ocean State
Pacific seas state: October 13, 2016
During early October 2016 the tropical Pacific SST anomaly was slightly cooler than -0.5C, the weak La Niña threshold. However, not all of the atmospheric variables have consistently been supporting weak La Niña conditions. Although the upper level winds in the tropical Pacific suggest weak La Niña, the lower level trade winds only became stronger than average in late September. The Southern Oscillation index and the pattern of cloudiness and rainfall across the equatorial Pacific do indicate weak La Niña conditions, but the lack of enhanced trade winds until recently makes us uncertain that La Niña is really here. Therefore, our current diagnosis remains ENSO-neutral. The collection of ENSO prediction models indicates SSTs near or slightly cooler than the threshold of La Niña during fall, then weakening to cool-neutral during winter.
Indian Ocean State
0.5 O above average sea surface temperature was observed in the eastern and southern sea of Sri Lanka.
14-day prediction: NOAA NCEP models predicts total rainfall between 35-45 mm is expected in Galle and Matara districts with adjacent sea expected to receive 45-55 mm total rainfall during 19th-25th October. For the same period Kalutara, Ratnapura, Hambegamuwa and Yala areas are expected to receive total rainfall between 25-35 mm while Colombo, Avissawella, Nuwara Eliya, Bandarawela and Monaragala areas expected to receive total rainfall between 15-25 mm. A total rainfall between 25-35 mm is expected for Gampaha, Kegalla, Kandy, Badulla and Ampara regions. For the period 26th October–1st November total rainfall between 45-55 mm is expected in Colombo, Gampaha, Kegalla, Ratnapura and Galle regions. Puttalam, Kurunegala, Kandy, Nuwara Eliya and Matara regions are expected to receive total rainfall between 35-45 mm. Total rainfall between 25-35 mm is expected for Mannar, Anuradhapura, Polonnaruwa, and Badulla regions.
Weekly prediction: IMD GFS model predicts rainfall between 10-20 mm for the whole island on 20th of October. On 21st Rainfall between 20-40 mm is expected for Mullaitivu and adjacent sea area including wester sea near the island. The rest of the island is expected to receive between 10-20 mm rainfall except for Anuradhapura and Hambantota regions. On 22nd the coastal regions of the island except for southern coast are expected to receive between 10-20 rainfall with north eastern sea receiving 40-70 mm rainfall. On 23rd northern, western and center regions are expected receive rainfall between 10-20 mm. On 24th south western coastal region is expected to receive rainfall between 20-40 mm with adjacent sea receiving rainfall between 40-70 mm rainfall. The rest of the country except for Matale, Kurunegala, Anuradhapura and Mannar is expected to receive rainfall between 10-20 mm. On 25th north western, center and south eastern regions of the country are expected to receive rainfall between 10-20 mm.
IMD WRF Model Forecast & IRI forecast:According to the IMD WRF model up to 64 mm of rainfall is expected in Chilaw and Puttalam regions on 21st. Several other north eastern and western coastal and regions of the country are expected to receive up to 35 mm rainfall. On 22nd the rainfall is expected to be increased with Kuchchaveli and the adjacent sea receiving rainfall up to 124 mm. Mullaitivu, Kilinochchi and Anuradhapura areas are expected to receive rainfall up to 65 mm. Up to 35 mm rainfall is expected in several other northern and western regions of the island.
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.
Temperature
NOAA CPC GFS model predicts 35-40 OC maximum temperature in eastern coastal belt including Monaragala and Polonnaruwa. 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.
Wind
The 850 mb level predicts up to 30 km/h north westerly wind in the southern half of the island including North Western province. Up to 18 km/h south westerly wind is expected for the northern half of the country. The 700 mb level predicts up to 36 km/h north westerly wind for the southern and central regions of the country while rest of the island is expected to receive wind with speed less than 20 km/h in the same direction.
MJO based OLR predictions
MJO shall not have a significant impact on the rainfall in Sri Lanka.
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