Highlights: Heavy rainfalls were observed throughout the country during the latter part of the previous week from 26th October -1st November. The highest rainfall of 160mm for the period was recorded in Galle and Matara on 30th. Minimum temperature of 15 OC was recorded from Nuwara Eliya district while the maximum temperature between 35-40 OCwas recorded from Trincomalee. Up to 20km/h north westerly winds were recorded in the Southern province. For the period from 2nd– 8th November the NOAA NCEP model predicts up to 85mm of rainfall for Colombo and adjacent sea regions. Up to 18km/h north westerly wind is expected in the whole country.
Monitoring
Rainfall
Weekly Monitoring:On 26th Mannar and Kudawewa area near the district border of Kurunegala and Puttalam received up to 20 mm rainfall. No rainfall was observed in any part of the island on 27th. Up to 20 mm rainfall was recorded in Kokkilai lagoon and adjacent sea area on 28th. On 29th Galle district received up to 120 mm rainfall while Matara district received up to 90 mm rainfall. Badulla and Monaragala districts received up to 80 mm rainfall. Kandy and Batticaloa districts received up to 40 mm rainfall. Up to 30 mm rainfall was observed in Hambantota, Nuwara Eliya and Ratnapura districts. Heavy rainfalls were observed in several parts of the island during 30th and 31st. On 30th Galle and Matara districts received up to 160 mm rainfall with adjacent southern sea receiving the same amount of rainfall. Mullaitivu, Vavuniya, Mannar, Kegalla and Ratnapura districts received up to 40 mm rainfall while Gampaha, Colombo, Monaragala, Kilinochchi and Anuradhapura districts received up to 30 mm rainfall. Up to 20 mm rainfall was observed in Jaffna, Kalutara, Nuwara Eliya, Kurunegala and Puttalam districts. On 31st Puttalam district received up to 120 mm rainfall while Karunegala and Anuradhapura districts received up to 90 mm rainfall. Up to 60 mm rainfall was observed in Vavuniya district. Up to 40 mm rainfall was observed in Ampara district and north western sea adjacent to the island. Mannar, Vavuniya, Kegalla, Ratnapura, Monaragala and Batticaloa districts received up to 30 mm rainfall. Up to 20 mm rainfall was observed in Kilinochchi, Matale, Kandy and Hambantota districts. For the past week, the RFE 2.0 tool shows rainfall up to 100mm in Mannar, Anuradhapura, Kurunega la, Puttalam, Gampaha, Galle, Badulla, Monaragala, Kandy and Matale districts. Up to 75mm of rainfall is shown for most of the country. Up to 25 mm rainfall is shown for Hambantota district. It also shows an above average rainfall of 100-200 mm in the Galle and Matara districts; and 50-100 mm in Vavuniya, Anuradhapura, Puttalam and Kurunegala districts. Below average rainfall of 50-100mm is shown for Jaffna, Trincomalee, Polonnaruwa, Colombo 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 October except for coastal regions of Galle district, where monthly average rainfall amount to 450mm/month. Rainfall did not exceed 210mm/month for the rest of the island. The CPC Unified Precipitation Analysis tool shows ~100mm 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 23rd–29th October the lowest temperature of 10-15OC was recorded in Nuwara Eliya. The maximum temperature recorded was between 35-40OC in Trincomalee region. The maximum temperature range in rest of the country 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 southern and northern regions of the country including Colombo region. Central region experienced an above average temperature of 0-1 OC.
At 850 mb level up to 20 km/h north westerly wind was experienced by the Southern province. The rest of the country experienced wind in the same direction with speed less than 18 km/h. At 700 mb level southern half of the island including Ampara district 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 18km/h in the same direction.
Ocean State
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 75-85mm in Colombo and adjacent area; 65-75mm 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 70-130 mm in Nuwara Eliya and 40-70 mm rainfall in Kandy, Badulla and Ratnapura areas for the 3rd of November. Rainfall between 20-40 mm is expected for rest of the central regions of the country including Hambantota. Rest of the island is expected to receive 10-20 mm rainfall. On 4th rainfall between 40-70 mm is expected for Nuwara Eliya and Badulla regions and rainfall between 20-40 mm in Kandy, Kegalla, Ratnapura and Monaragala regions. Rest of the island is expected to receive 10-20 mm rainfall. On 5th entire island is expected to receive rainfall between 10-20 mm except for Anuradhapura, Vavuniya and Kilinochchi. Rainfall between 40-70 mm is expected in western and south western sea regions adjacent to the island. On 6th the whole island is expected to receive rainfall between 10-20mm except for Kurunegala and Matale regions. On 7th rainfall between 10-20mm is expected in most parts of the country. On 8th surrounding areas of Hambantota, Trincomalee and Vavuniya are expected to receive rainfall between 10-20mm. No rainfall is expected in any part of the country on 8th.
IMD WRF Model Forecast & IRI forecast:According to the IMD WRF model up to 125 mm of rainfall is expected in Ratnapura region on the 4th. Colombo, Kalutara, Galle, Kegalla, Yala and Puttalam regions are expected to receive up to 65 mm rainfall with Ampara, Monaragala, Badulla, Matara, Gampaha and Kurunegala regions expected to receive 35 mm rainfall. On 5th surrounding areas of Ratnapura shall receive rainfall up to 64mm, and western region of the country shall experience rainfall up to 35 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.
Temperature
NOAA CPC GFS model predicts 35-40OC maximum temperature in Monaragala and Ampara districts. The maximum temperature for the rest of the island 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 18 km/h north westerly wind for the entire country. The 700 mb level predicts up to 20km/h north westerly wind in the Southern province. The rest of the country experienced wind in the same direction with speed less than 18 km/h.
MJO based OLR predictions
MJO shall not have a significant impact on the rainfall in Sri Lanka.
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