Weekly Hydro-meteorological Report, 12 September, 2013

Highlights

Monitoring and Prediction
Puttalam to Galle districts and Jaffna peninsula are likely to receive heavy rainfall on coming two days (14th & 15th September) and shall persist till 16th September. However, ongoing rainfall is likely to decrease gradually till 24th September. Significant rainfall is note predicted for the entire country, except for Eastern coasts which significant rainfall is likely to observe during 13th-14th September.

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Summary

Monitoring


Weekly Monitoring:During 3rd-10th September 2013, rainfall ranged 5-60 mm. Maximum rainfall was observed for small regions at Ampara and Batticaloa districts on 3rd & 5th September. Northern peninsula received more rainfall than the remaining parts of the island.


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:Southern 1/3rd of the island shall receive 5-55 mm of rainfall and Northern 1/3rd of the island shall receive 55-105 mm of rainfall during 11th-17th September 2013.

IMD WRF Model Forecast & IRI forecast:For 14th & 15th of September, IMD WRF model predicts less than 65 mm of rainfall for the coastal regions of Puttalam-Galle districts and shall spread to nearby regions (including Jaffna peninsula) in a reducing manner. NOAA model predicts high rainfall (5-75 mm/week) for Colombo-Galle districts and Jaffna peninsula during 11th-16th September.

1 Month Prediction:Overall- Ongoing rainfall is likely to decrease gradually till 24th. No significant rainfall events are expected. Western Slopes – The rainfall pattern persisting in the entire country shall be observed in this region, but rainfall is likely to be constant during 19th-25th September. Western Coast – The rainfall shall increase till 16th and thereafter it shall reduce till 23rd. Eastern Slopes– Rainfall shall decrease till 19th September and rainfall is note predicted thereafter. Eastern Coast – Significant rainfall event is likely to be present during 13th-14th September. Thereafter rainfall shall reduce till 21st. Northern region- The rainfall pattern persisting in the entire country shall be observed in this region. Southern Region- Rainfall is likely to increase during 14th-16th & shall decrease in a same rate till 19th. Rainfall is not predicted during 19th-23rd September.

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 1st-7th September 2013.
MJO STATE :MJO is at phase 2 and 3 and shall influence Sri Lanka rainfall.