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Friday, November 2, 2012

Weekly Hydro-meteorological Report, 01 November 2012


Monitoring and Prediction
The tropical storm that started to the West of Sri Lanka propagated North-Westwards drenching the Northeastern seaboard in particular and the rest of the island considerably as well as it intensified to cyclonic speeds. This is an early start to the cyclone that usually lasts from November till February– there has only been one that has made landfall in Sri Lanka recorded during October for the past 140 years. The anomalously warm sea surfaces to the east of Sri Lanka is one of the factors that contributes to enhanced cyclogenesis. The forecasts for the next week are for continued wet weather but only reaching a weekly accumulation of about 75mm..

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Weekly Monitoring: During 25th – 30th October Sri Lanka received very high amount of rainfall especially due to the tropical storm NILAM-12. Rainfall ranged between 0- 180 mm with highest amount of precipitation observed in Trincomalee area on the 29th of October 2012. On the 27th South Western parts received high rainfall and on 28th and 29th Jaffna Peninsula and North Eastern parts of the country received extremely high rainfall while rest of the country also received very high rainfall. High rainfall continued to persist in North Eastern and South Western regions while rainfall in other parts reduced considerably compared to the previous couple of days.

Monthly Monitoring: In September, Central and South Eastern regions of the country received below average rainfall and the rest of the country received above average rainfall. Western, South Western and Jaffna peninsula regions were particularly wetter than normal.


7-day prediction: During this week, the entire country shall receive rainfall upto 95 mm.

IMD WRF Model Forecast & IRI forecast: Updates of WRF model predictions are not available at this time. NOAA models forecast 70 mm of rain for the entire country.

1 Month Prediction: Overall- Rainfall shall decrease gradually during 25th-29th & it shall increase gradually during 29th October-2nd November. Thereafter again rainfall shall decrease till 4th November. Thereafter rainfall shall increase gradually till 11th November. Western Slopes- Rainfall shall graduall decrease until 1st of November. Then it shall graduall increase to a maximum around the 10th. Thereafter rainfall shall decrease. Eastern slopes- Rainfall shall graduall decrease until 30th. Then it shall gradually increase till 11th November. Northern- Rainfall shall decrease until 29th of October and fluctuate thereafter until 20th of November.

Seasonal Prediction: As per IRI Multi Model Probability Forecast for November 2012 to January 2013, issued in October 2012, there is a 50%-60% probability for temperature to be above normal in the country while the rainfall is to be climatological.

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