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Friday, November 2, 2012

Weekly Hydro-meteorological Report, 25 October 2012


Monitoring and Prediction
The drought during the Yala season abated at the start of September and now as is seasonable with the start of the Maha season, we have heavy rainfalls. For the same reasons that Yala was drought ridden (warm Central Indian Ocean and Pacific Ocean surface temperatures), Sri Lanka and the sea towards eastern Africa is likely to have a wetter and warmer period till December.

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Weekly Monitoring: During 17th-22nd of October, rainfall ranged between 0-100 mm. Heavy rain was reported in the Southern half of the island and Jaffna Peninsula on the 18th. In the next 4 days less rain was observed in South East while the rest of the country received heavy rainfall.

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, North and South eastern regions shall receive 35- 55 mm rainfall and the rest of the country shall receive rainfall up to 65 mm.

IMD WRF Model Forecast & IRI forecast: IMD WRF Model predictions are not available for this week. NOAA models forecast 50- 75 mm rainfall in Jaffna peninsula and 100- 150 mm rainfall in the south. The rest of the country shall receive in between of rainfall.

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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