Weekly Hydro-meteorological Report, 22 August, 2013

Highlights

Monitoring and Prediction
During past week (15th-21st August) rainfall was quite low compared to the month of July. Kalutara district is likely to receive heavy rainfall on tomorrow (23rd August) compared to rest of the regions of Sri Lanka. Ongoing rainfall is likely to decrease gradually till the end of August, but rainfall shall not exceed 2 mm/day. No significant rainfall events are predicted for the entire country, except for the Southern regions. Southern regions are likely to experience significant rainfall event during 23rd-25th August.

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Summary

Monitoring


Weekly Monitoring:Rainfall ranged between 5-30 mm during 14th-19th August 2013. Maximum rainfall observed in Jaffna district on 19th August. However, entire Sri Lanka showed dry condition during this period.


Monthly Monitoring:Southwestern regions of Sri Lanka received an above average rainfall during the month of July. The entire country received less than 15 mm of daily rainfall, with Colombo and Gampaha districts receiving the highest rainfall during the month (14 mm/day).

Predictions

7-day prediction:Southwestern regions of Sri Lanka shall receive 5-35 mm of rainfall and shall spread northeastward in a reducing manner during 21st-27th August 2013.

IMD WRF Model Forecast & IRI forecast:For 23rd of August, IMD WRF model predicts less than 65 mm of rainfall for coastal regions of Kalutara district and it shall spread most nearby districts (Matara - Puttalam, Kegalle and Ratnapura in a reducing manner. NOAA model predicts more or less same moisture condition for the entire country, except Mannar district shall receive dry condition during 21st-26th August.

1 Month Prediction:Overall- Ongoing rainfall is likely to decrease gradually till the end of August, but rainfall shall not exceed 2 mm/day. No significant rainfall events are predicted. Western Slopes – Low amount of daily rainfall (less than 3 mm/day) shall persist till the end of August. Western Coast – Rainfall is not predicted during 24th-26th August and low amount of rainfall is likely to observe till the end of month. Eastern Slopes– Rainfall shall increase gradually after 28th. However, significant rainfall events are not expected till the end of August. Eastern Coast – The rainfall shall remain more or less constant (less than 2 mm/day) till 30th of August. Northern region- The rainfall pattern persisting in the Eastern Coasts shall be observed in this region. Southern Region- The rainfall shall increase gradually till 24th and shall decrease in a same rate. Rainfall shall increase gradually after 28th of August. However, significant rainfall event is likely to be observe during 23rd-25th August.

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

PACIFIC SEAS STATE August 15, 2013 :During July through early August the observed ENSO conditions remained neutral. Most of the ENSO prediction models indicate a continuation of neutral ENSO through the remainder of 2013 & into early 2014. However, a few (mainly statistical) models call for cooling towards borderline or weak La-Nina conditions for northern autumn into winter. While a few others (mainly dynamical) forecast some warming towards borderline or weak El-Nino conditions for this same time frame.

INDIAN OCEAN STATE :The sea surface temperature around Sri Lanka was neutral during 11th-17th August 2013.
MJO STATE :MJO is neutral and shall not influences the rainfall in Sri Lanka.