Weekly Hydro-meteorological Report, 24, November 2016

Highlights:


The NOAA NCEP model predicts heavy rainfall (up to 125 mm) from 23rd– 29th November for the coastal regions of Colombo. Heavy rainfall events were experienced throughout the island during 16–22 November, with the highest recorded rainfall of 140 mm on the 22nd in Hanwella and Giriulla. 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 easterly winds were experienced by the entire country.
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Summary

Monitoring


Weekly Monitoring: On November 16th received rainfall up to 50 mm by Western province, Kilinochchi district and western and north western sea regions adjacent to the island; up to 30 mm by Puttalam, Kegalla, Ratnapura and Badulla districts; up to 20 mm by North Central, Central, Eastern and Southern provinces including Jaffna, Mullaitivu, Mannar, Trincomalee and Kurunegala districts. On November 17th rainfall was received, up to 50 mm in North Central and North Western provinces including Gampaha, Colombo and Jaffna districts; up to 30 mm in Sabaragamuwa, Eastern provinces, Kalutara, Kandy, Badulla, Kilinochchi, Mannar, Vavuniya and Mullaitivu districts; up to 90 mm along the adjacent north eastern sea region; and up to 20 mm in rest of the districts in Sri Lanka. On November 18th rainfall was received, up to 80 mm by Kilinochchi, Polonnaruwa, Ampara, Badulla and Monaragala districts; up to 60 mm in the coastal areas of Ampara district and the adjacent eastern sea area; up to 50 mm by the Central and Western provinces, with Jaffna, Mannar, Kegalla, Anuradhapura and Vavuniya districts; up to 30 mm by Mullaitivu, Puttalam and Ratnapura districts; and up to 20 mm in rest of the districts. November 19th received rainfall, up to 90 mm in Jaffna peninsula and adjacent northern sea; up to 80 mm in Kilinochchi district; up to 50 mm in Mullaitivu, Matale, Kandy, Batticaloa and Ampara districts; up to 30 mm in Trincomalee, Mannar, Vavuniya, Anuradhapura, Polonnaruwa and Kurunegala districts; and up to 20 mm in Colombo, Kalutara, Galle, Badulla and Monaragala districts. On November 20th rainfall was received, up to 50 mm in Jaffna district; up to 20 mm in Kilinochchi, Mannar and Puttalam districts; and up to 80 mm by the Eastern Sea adjacent to the island. On November21st rainfall was received up to 80 mm by Matara, Hambantota districts and adjacent eastern and western sea regions of the island; up to 50 mm in Jaffna and Galle districts; up to 30 mm in Kilinochchi, Mullaitivu, Kalutara, Ratnapura and Batticaloa districts; and up to 20 mm by Mannar, Anuradhapura, Polonnaruwa and Trincomalee districts. On November 22nd surrounding areas of Giriulla and Hanwella received rainfall up to 140 mm; Puttalam, Gampaha and Kegalla districts up to 90mm of rainfall, Kilinochchi and Jaffna districts received up to 50 mm of rainfall; and Mullaitivu, Vavuniya, Kandy, Nuwara Eliya and Galle districts received up to 20 mm of rainfall.


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 amounted 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.

Predictions

14-day prediction:From 23rd-29th November, the NOAA NCEP models predicts total rainfall up to 125 mm for coastal regions of Colombo district; 115-125 mm in Ampara, Batticaloa, Gampaha, Nuwara Eliya, Ratnapura, Galle and Kegalla districts; 95-105 mm in Gampaha, Ratnapura, Kegalla and Galle districts; 85-95 mm in Polonnaruwa, Kurunegala and Matara districts; 75-85 mm in Matale, Kandy Nuwara Eliya, Monaragala and Badulla districts; and total rainfall between 45-55 mm in Puttalam, Anuradhapura and Mullaitivu districts. From 30th November – 6th December a total rainfall between 125-135 mm is expected in the coastal regions of Batticaloa; 115-125 mm in the coastal regions of Colombo; 105-115 mm in Batticaloa, Trincomalee, Ratnapura and Galle districts, and more than 65 mm in rest of the country.

IMD WRF Model Forecast & IRI forecast:: According to the IMD WRF model, on the 25th up to 35 mm of rainfall is expected in Ratnapura and Colombo districts; and up to 7 mm of rainfall in rest of the south western regions of the island. On 26th, rainfall is expected to increase with Ampara district receiving rainfall up to 64 mm and Ratnapura, Trincomalee, Nuwara Eliya, Badulla, Monaragala and Kegalla regions receiving rainfall up to 35 mm. Most of the eastern and southern regions of the country are expected to receive up to 7 mm of rainfall.

Seasonal Prediction:As per IRI Multi Model Probability Forecast for December to February 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

PACIFIC SEAS STATE During mid-November 2016 the tropical Pacific SST anomaly was slightly cooler than -0.5C, the threshold for weak La Niña. Also, most of the atmospheric variables across the tropical Pacific have been consistent with weak La Niña conditions. The upper and lower atmospheric winds have been suggestive of a strengthened Walker circulation, and the cloudiness and rainfall have also been consistent with weak La Niña conditions. The collection of ENSO prediction models indicates SSTs near or slightly cooler than the threshold of La Niña during the remainder of fall, persisting through mid-winter, then weakening to cool-neutral by later winter.
INDIAN OCEAN STATE :0.5 ^OC above average sea surface temperature was observed in the northern, north eastern and eastern sea of Sri Lanka.
MJO STATE :MJO shall enhance the rainfall during the next 10 days and shall not have a significant impact on the rainfall in Sri Lanka for the following 5 days.