Cyclone Gudrun in January 2005 and modelling its hydrodynamic consequences in the Estonian coastal waters

Meteorological parameters of windstorm Gudrun on 8–9 January 2005 and its hydrodynamic and environmental consequences are analysed on the basis of observational data and hydrodynamic modelling. The study focuses mainly on describing events and reception in Estonia. We estimate that in meteorological terms, the cyclone was among the five most powerful ones in recorded history. Considering also the new highest storm surge record (275 cm in Pärnu), extensive property damage and massive media coverage, it became the most influential natural disaster in Estonia. Using a shallow sea 2D hydrodynamic model with a 1-km grid step, a hindcast modelling study of the sea level was carried out. Hydrodynamic simulations suggest that an inflow of 24 km3 (5.4% of the Gulf's average volume) occurred in the Gulf of Riga. The sub-basin of the Väinameri was nearly entirely flushed through by more saline and nutrient-poorer water from the Baltic Proper. The simulated current velocities, sea levels and wave parameters indicate that prominent coastline changes and replacement of sediments could have occurred within a single day.