Weekly Hydro-meteorological Report, 23 August 2012

Summary

Monitoring

Weekly Monitoring: During the last week (15^th- 21^st August) rainfall ranged between 0mm- 50 mm. 5mm-50mm rainfall was experienced in the Western, South Western, Central and some parts of the Northern region during 15^th -17^th August. Dry conditions prevailed during 19^th-20^th while a scattered rainfall between 5mm-10mm was experienced particularly in the lower part of the Mahaweli basin and some parts of the western region.

Monthly Monitoring: During July, southern half of the island experienced a below average rainfall with an increased below average particularly in the Western and South Western regions. It clearly reflects the deficit of the South West Monsoon rainfall up to now. The rest of the island experienced an above average rainfall with a higher intensity in the Trincomalee district while some parts of the Moneragala district also experienced an above average rainfall.

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Predictions

7 Day Prediction: For the coming week an accumulated rainfall of 05mm - 45 mm is predicted for the whole island with more rainfall for the South Western, Western and Southern regions.

IMD WRF Model Forecast & IRI forecast: On the 25^th of August IMD WRF model predicts rainfall between 1mm-125mm, with high rainfall (36mm-125mm) for the Gampaha, Colombo, Kalutara and Galle districts. The higher rainfall up to about 125mm is predicted particularly for Colombo and Kalutara districts. 1mm-36mm rainfall is predicted for Batticaloa, Ampara and some parts of Badulla and Moneragala Districts. Same predictions are made on the 26^th with the maximum rainfall of 125mm shall be further spread to Galle and Matara districts. NOAA models forecast up to 50mm for the northern half of the country while up to 20mm rainfall for the rest of the country.

1 Month Prediction:  Overall there shall be no high rainfalls expected. A rapid decrease of rainfall shall be expected till the 24^th of August followed by a rapid increase by 25^th. Thenafter it shall again decrease rapidly till the 27^th. Rainfall shall increase dramatically till the 31^st of August and thenafter quite steady conditions shall be observed till the 8^th of September. Westernslopes- A rapid increase of rainfall till the 25^th shall be expected followed by a rapid dicrease till the 27^th. Thenafter rainfall shall show an increasing trend with some fluctuations till the 8^th of September. It shall agin show a sudden drop till the 10^th  followed by a rapid increase till the 13^th. Peak rainfalls shall be expected on the 25^th of Aug, 8^th and  13^th of September.Eastern slopes- A rapid increase of rainfall shall be expected after 26^th of August till the 30^th . Thenafter it shall decrease slowly till the 8^th September followed by a rapid drop till the 10^th. Again it shall increase rapidly till the 14^th. Northern- Highly fluctuated rainfall shall be expected during coming month of period. Maximum rainfall shall not exceed 4mm.

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