Case Study

Flash Floods in Slovenia

This case-study presents the analysis of catastrophic flash floods in Slovenia that occurred on 18 September 2007. The flooding caused five casualties and huge material damage, estimated to more than 150 million Euro.

NWP models forecasted precipitation amounts of up to 100 mm/24h. That was the reason that the forecaster issued a warning for the precipitation at a rate of more than 100 mm/day, but the real values were much higher.

Besides analyzing synoptic and mesoscale conditions, that caused the extreme amount of precipitation, the objective of this study is also to show how nowcasting material can help a forecaster to issue additional warnings.

The synoptic analysis shows that on the day of the catastrophic event the area of low pressure was situated over the Northern Europe. A cold front was approaching the Alps and over Slovenia a series of prefrontal convective developments took place. In many regions in Slovenia the precipitation values were extremely high (>100 mm/day) with the maximum precipitation of 304 mm/24h officially measured in Kneske Ravne.

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Filed under Keywords:

Nowcasting, Precipitation, Convection, Supercell, Hydrology, Flash Flood