Highlights: Wet weather conditions prevailed in many parts of the country during 19th-25th October, with the highest recorded rainfall of 90mm in Kegalle on 24th. Minimum temperature of 15 OC was recorded from Nuwara Eliya district while the maximum temperature between 35-40 OC was recorded from Vavuniya, Mannar and Anuradhapura districts. Up to 30km/h north westerly winds were recorded in the southern half of the country. For the period from 26th October – 1st November the NOAA NCEP model predicts up to 55mm of rainfall for Colombo, Ratnapura, Galle and Matara regions. Up to 15km/h westerly wind is expected in the southern regions of the country.
Monitoring
Rainfall
Weekly Monitoring:Up to 50mm of rainfall was observed on the 19th in Nelliady in Jaffna, and the coastal areas of Kalkuda in Batticaloa. Welikanda, Kandakadu and Trikonamadu areas in Polonnaruwa received up to 30mm rainfall; and up to 20mm rainfall was observed in the western regions of Anuradhapura and northern regions of Monaragala. On 20th up to 20 mm of rainfall was observed in Anuradhapura and Polonnaruwa. On 21st the Maradankadawela region of Anuradhapura, and Kalkuda area received up to 30mm rainfall with adjacent sea area receiving up to 50mm rainfall. Up to 20mm rainfall was observed in several regions of Puttalam and Kurunegala districts including Avissawella and Deniyaya. On 22nd up to 50mm rainfall was observed in coastal regions of Colombo district and Baduluwela region of Monaragala district. Gampaha and western sea region received up to 30mm rainfall. Vavuniya, Trincomalee, Badulla and Kurunegala, Madampe and Ratnapura received up to 20mm rainfall. On 23rd up to 70 mm rainfall was observed in surrounding areas of Ingiriya in Kalutara; Colombo district received up to 50mm rainfall; Gampaha, Galle, Kegalle and Ampara districts received up to 20mm of rainfall and the western and north eastern coastal areas received up to 50mm of rainfall. On 24th up to 90mm of rainfall was observed in Kegalle district and up to 50mm rainfall was observed in Kurunegala, Gampaha, Ratnapura, Nuwara Eliya and Kandy districts; and Puttalam, Kalutara, Galle, Matara and Ampara districts received up to 20 mm rainfall; the area near the eastern sea received up to 60mm rainfall while south western sea received up to 30mm rainfall. For the past week, the RFE 2.0 tool shows rainfall up to 100mm in Kegalla and Ratnapura. Up to 75mm of rainfall is shown in Colombo and Gampaha districts including several areas of Puttalam, Kurunegala, Kalutara, Anuradhapura and Monaragala districts. Rainfall between 10-25 mm is shown for several northern and south eastern regions of the island. It also shows an above average rainfall of 25-50 mm in the Kegalle district. Below average rainfall of 50-100mm is shown for Mannar, Vavuniya, Matale and Monaragala regions, and 25-50 mm for most parts of the island.
Monthly Monitoring: Below average rainfall conditions were experienced in the entire island in the month of September. Monthly average amount to 120mm/month in Ahungalla and Ratnapura town while in all other area rainfall did not exceed 60mm/month. The CPC Unified Precipitation Analysis tool shows ~75mm of total rainfall in Ratnapura, ~25 mm of rainfall in Colombo, Kegalle, Nuwara Eliya, Bandarawela and Matara
From 16th–22nd October the lowest temperature of 10-15OC was recorded in Nuwara Eliya. The maximum temperature recorded was between 35-40OC in Vavuniya, Mannar and Anuradhapura districts. The maximum temperature range in Kandy, Kegalle, Badulla and Balangoda was 20-25OC. The maximum temperature in the rest of the country was between 30-35 OC. During this period an above average temperature of 0-3OC was observed by the entire country except for Nuwara Eliya and Badulla regions where an above average temperature of 0-1OC was observed.
At 850 mb level up to 30 km/h north westerly wind was experienced by the southern half of the island including Ampara district. The rest of the country experienced wind in the same direction with speed less than 20 km/h. At 700 mb level Southern province experienced north westerly winds with a speed of up to 30 km/h while rest of the country experienced winds with a speed less than 20km/h in the same direction.
Ocean State
Pacific seas state: October 20, 2016
DDuring mid-October 2016 the tropical Pacific SST anomaly was slightly cooler than -0.5C, the threshold for weak La Niña. However, not all of the atmospheric variables have been supporting weak La Niña conditions for a sufficient duration to constitute good ocean-atmospheric coupling. Although the upper level winds suggest weak La Niña, the lower level trade winds only became stronger than average in mid-September. The Southern Oscillation index and the pattern of cloudiness and rainfall do indicate weak La Niña conditions. The lack of enhanced trade winds until recently makes us hesitate to say La Niña has really begun, so our 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.(Text Courtesy IRI)
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:
14-day prediction: From 26th October to 1st November, the NOAA NCEP models predicts total rainfall, between 45-55mm in Colombo, Ratnapura, Galle and Matara; 35-45mm in Gampaha, Kegalle, Balangoda, and Hambantota; 25-35mm in Jaffna, Vavuniya, Mannar, Nuwara Eliya and Bandarawela; and total rainfall between 5-15mm is expected in most parts of the country. Increased total rainfall between 75-85mm is expected around the coastal areas of Colombo and adjacent sea during 2nd-8th November.
Weekly prediction: IMD GFS model predicts rainfall between 10-20mm for the whole island except for Northern, Eastern and Western provinces for the 27th of October. On 28th Rainfall between 10-20mm is expected for central and south eastern regions of the country including several regions of Puttalam and Polonnaruwa districts. On 29th north, north eastern and south eastern regions of the island are expected to receive rainfall between 10-20mm with south eastern sea receiving 20-40 mm rainfall. On 30th the whole island is expected to receive rainfall between 10-20mm except for Kurunegala and western coastal regions of the country. On 31st Nuwara Eliya, Kandy, Anuradhapura and southern sea adjacent to the island are expected to receive rainfall between 20-40mm. The rest of the country except for coastal regions of Western province is expected to receive rainfall between 10-20mm. On 1st surrounding areas of Ratnapura and southern coastal area of the island are expected to receive rainfall between 20-40mm while rest of the country is expected to receive rainfall between 10-20mm.
IMD WRF Model Forecast & IRI forecast:According to the IMD WRF model up to 35mm of rainfall is expected in Balangoda and Ampara regions on the 28th. Eastern, south eastern coastal and central regions of the country are expected to receive up to 7mm rainfall. On 29th western and eastern coastal regions shall receive rainfall up to 7mm, and rainfall shall decrease in the rest of the country.
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, Hambantota and Polonnaruwa. The maximum temperature of Ratnapura and Badulla areas will be between 25-30 OC.while for the rest of the country the maximum temperature will range between 30-35OC. For the same period minimum temperature is expected in Nuwara Eliya to be between 15-20OC.
Wind
The 850 mb level predicts up to 15 km/h westerly wind in the southern region of the island. Up to 10km/h wind in the same direction is expected for the rest of the country. The 700 mb level predicts up to 10km/h north westerly wind for the whole country.
MJO based OLR predictions
MJO shall not have a significant impact on the rainfall in Sri Lanka.
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