Weekly Hydro-meteorological Report, 13 September 2012

Summary

Monitoring

Weekly Monitoring: During the last week (6th- 11th September) rainfall ranged between 0 mm- 70 mm. Heavy rainfall was observed during 6th -9th September in South and Western regions of the island which diminished on the 9th. A scattered rainfall was experienced on the 10th in most parts of the country. Rain ceased completely on the 11th for the whole island except for North-Central and South-Eastern regions of the island, which experienced slight rainfall.

Monthly Monitoring: During August South Western, Western and Some regions of Badulla and Ampara districts experienced an above average rainfall with quite high positive anomaly in the South Western region. The rest of the country experienced below average rainfall during this period.

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Predictions

7-day prediction: During this week, an accumulated rainfall of 25 mm – 95 mm is predicted for the South western regions of the island.

IMD WRF Model Forecast & IRI forecast: On the 14th IMD WRF model predicts 1 mm-8 mm rainfall for Jaffna Peninsula. For the same day model predicts 2 mm- 36 mm rainfall for North Western and Western regions and less than 64.5 mm rainfall for South-Western parts of the country with maximum rainfall shall expect in Galle area. On the 15th model predicts an increased rainfall of 2-65 mm for Colombo, Negambo and Chilaw areas. Rainfall shall cease in Jaffna Peninsula while South-Western regions shall experience rainfall of 1-35 mm. NOAA models forecast Predicts up to 20 mm total rainfall for the whole country.

1 Month Prediction: Overall- Rainfall shall fluctuate between 0 and 3 mm. For the period of 16th-18th & 21st-25th rainfall is not predicted. Western Slopes- During 14th-17th rainfall shall decrease & it shall increase drastically till 19th. Thereon it shall decrease till 21st.Rainfall is not predicted for the 21st-23rd. Rainfall shall increase drastically upto 6 mm of daily rainfall during 23rd-30th. Thereon rainfall shall fluctuate between 4-6 mm during October. Eastern slopes- Rainfall shall decrease drastically during 14th-16th. During 16th-23rd rainfall shall increase gradually, with minor fluctuation during 18th-20th. Thereon rainfall shall decrease till 28th. Rainfall is not predicted for 28th-30th. Thereon rainfall shall increase till 7th October and shall decrease thereafter. Northern- No Significant rainfall shall be expected and rainfall is not predicted for the most of the periods in Septemeber.

Seasonal Prediction: As per IRI Multi Model Probability Forecast for September 2012 to November 2012, issued in August 2012, there is a 50%-60% probability for temperature to be above normal in the country while the rainfall is to be climatological.