Highlights: Wet weather conditions prevailed in many parts of the country during the previous week from 2rd-7th November. The highest rainfall of 90 mm for the period was recorded in adjacent south eastern sea on 3rd. Minimum temperature of 15 OC was recorded from Nuwara Eliya district while most parts of the island recorded a maximum temperature between 30-35 OC Up to 20 km/h north westerly winds were recorded in the southern region of the country. For the period from 2nd– 8th November the NOAA NCEP model predicts up to 85 mm of rainfall for Colombo and adjacent sea regions.
Weekly Monitoring:On 3rd Kalkuda area received up to 70 mm rainfall while nearby sea including south eastern sea regions of the island received up to 90 mm rainfall. Up to 50 mm rainfall was received in Mannar, Puttalam, Kurunegala and Matale districts and up to 30 mm rainfall was received by Vavuniya, Anuradhapura, Ratnapura, Kalutara, Galle, Kandy Badulla and Monaragala districts. Batticaloa, Matale, Ampara, Kilinochchi, and Mullaitivu and Hambantota districts received up to 20 mm rainfall. On 4th Colombo coastal areas and south western sea regions near the island received up to 80 mm rainfall. Up to 50 mm rainfall was received by Gampaha, Ratnapura, Kalutara and Galle districts. Kegalla district received up to 40 mm rainfall while Matara, Nuwara Eliya, Kandy, Puttalam, Kurunegala, Monaragala and Ampara districts received up to 30 mm rainfall. Matale, Hambantota, Anuradhapura and Badulla districts received up to 20 mm rainfall. On 5th Kalutara, Galle and Matara districts received up to 50 mm while Colombo, Kegalla and Ratnapura districts received up to 40 mm rainfall. Up to 30 mm rainfall was received by Gampaha and Hambantota districts and up to 20 mm rainfall was received by Monaragala and Nuwara Eliya districts. On 6th Galle and Kalutara districts received up to 50 mm rainfall while Trincomalee, Gampaha, Matara and Ratnapura districts received up to 30 mm rainfall. Up to 20 mm rainfall was received by Mannar, Mullaitivu, Vavuniya, Hambantota, Anuradhapura and Polonnaruwa districts. Adjacent southern sea received up to 80 mm rainfall. On 7th surrounding areas of Hambegamuwa in Monaragala district received up to 80 mm rainfall while Silavatturai and Paraiyanalankulam of Mannar district including Ratnapura district received up to 50 mm rainfall. Tambuttegama region near the Anuradhapura and Kurunegala district border received up to 30 mm rainfall while several areas of Vavuniya, Jaffna, Batticaloa, Polonnaruwa and Hambantota districts received up to 20 mm rainfall. For the past week, the RFE 2.0 tool shows rainfall up to 100 mm in Colombo, Kalutara, Ratnapura, Kegalla, Gampaha, Galle, Matara, Monaragala, Hambantota and Mannar districts. Up to 75 mm of rainfall is shown for Puttalam, Kurunegala, Trincomalee, Kandy and Nuwara Eliya districts. Up to 50 mm rainfall is shown for most of the country. It also shows an above average rainfall of 25-50 mm in the Western and Southern provinces. Below average rainfall of 50-100 mm is shown for Kurunegala, Matale, Anuradhapura, and Ampara districts, 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 October except for coastal regions of Galle district, where monthly average rainfall amount to 450 mm/month. Rainfall did not exceed 210 mm/month for the rest of the island. The CPC Unified Precipitation Analysis tool shows ~100 mm of total rainfall in Gampaha, Colombo, Ratnapura, Galle, Matara, Anuradhapura, Mannar, Vavuniya,, Matale, Kandy and Nuwara Eliya districts ; and ~25 mm of total rainfall in Ampara, Badulla, Monaragala, Kegalla and Jaffna districts.
From 30th October–5th November the lowest temperature of 15-20 OC was recorded in Nuwara Eliya. The maximum temperature recorded in Kandy, Badulla, Kegalla and Ratnapura regions was between 25-30 OC. The maximum temperature range in rest of the country was 30-35 OC. During this period an above average temperature of 0-1 OC was recorded by the western and eastern coastal regions. Northern and central regions experienced an above average temperature of 0-3 OC.
At 850 mb level up to 20 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 province experienced north westerly winds with a speed of up to 20 km/h while rest of the country experienced winds with a speed less than 18 km/h in the same direction.
Pacific seas state: October 20, 2016
During 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 western sea of Sri Lanka.
14-day prediction: 14-day prediction: From 2nd-8th November, the NOAA NCEP models predicts total rainfall, between 75-85 mm in Colombo and adjacent area; 65-75 mm in Galle, Matara and Ratnapura regions; 45-55 mm in Jaffna, Ampara, Gampaha and Kegalla regions; and total rainfall between 25-35 mm is expected in most parts of the country. For the period 9th-16th November total rainfall between 75-85 mm is expected in Colombo. Gampaha, Kegalla, Ratnapura, Puttalam, Kurunegala and Galle regions are expected to receive total rainfall between 45-55 mm. Total rainfall between 35-45 mm is expected in Central and North Central provinces.
Weekly prediction: : IMD GFS model predicts rainfall between 1-10 mm is expected for the whole island except for northern and western regions on 11th. On 12th rainfall between 40-70 mm is expected for Nuwara Eliya and Badulla regions and rainfall between 20-40 mm in Kandy, Kegalla and Ratnapura regions. Rest of the island is expected to receive 1-10 mm rainfall except for northern and north eastern regions. On 13th Colombo and adjacent sea are expected to receive rainfall between 70-130 mm with Gampaha and Kalutara regions expected to receive 40-70 mm. Rainfall between 20-40 mm is expected in Galle, Kalutara, Kegalla, Ratnapura and Nuwara Eliya regions while rest of the country except for south eastern region of the island expected to receive rainfall between 1-10 mm. On 14th the whole island is expected to receive rainfall between 1-10 mm. On 15th rainfall between 20-40 mm is expected in Colombo, Kegalla, Kandy, Mannar, Puttalum and Nuwara Eliya while rest of the country expected to receive 1-10 mm rainfall. On 16th surrounding areas of Kegalla and Ratnapura are expected to receive rainfall between 20-40 mm while rest of the country expected to receive 1-10 mm rainfall except for Polonnaruwa and Dehiattakandiya regions.
IMD WRF Model Forecast & IRI forecast:According to the IMD WRF model up to 64 mm of rainfall is expected in Yala region of Southern province on the 11th. Monaragala, Badulla, Nuwara Eliya and Ratnapura regions are expected to receive up to 35 mm rainfall with rest of the south eastern regions expected to receive 35 mm rainfall. On 5th surrounding areas of Tissamaharama and Kilinochchi shall receive rainfall up to 124 mm, and rest of the northern region including Kandy, Ratnapura, Matara and Monaragala regions shall experience rainfall up to 35 mm. Southern sea near the island is expected to receive up to 64 mm rainfall.
Seasonal Prediction:As per IRI Multi Model Probability Forecast for November to January 2017, the total 3-month precipitation shall be climatological for the whole island. 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 35-40 OC maximum temperature in Tanamalwila area of Monaragala district. The maximum temperature for the rest of the island will range between 30-35 OC.For the same period minimum temperature is expected in Nuwara Eliya, Kandy, Ratnapura and Badulla to be between 15-20 OC.
The 850 mb level predicts up to 20 km/h north easterly wind for northern and north western regions of the country. Up to 18 km/h wind in the same direction is expected for the rest of the country. The 700 mb level predicts up to 20 km/h north easterly wind in the northern and eastern regions of the island. The rest of the country expected to experience wind in the same direction with speed less than 18 km/h.
MJO based OLR predictions
MJO shall significantly suppress rainfall in Sri Lanka over the next 15 days.