Description

Meteorological background

In the week before the flood, an upper-level trough extending from Scandinavia to southern Europe affected the Adriatic region. Advected warm and humid air led to the formation of several cyclones with frontal disturbances, causing moderate precipitation and variable winds across the Adriatic. On the night of 25–26 November, a low-pressure system formed over the Gulf of Genoa and moved towards the northern Adriatic, strengthening southerly and southeasterly winds across the basin. The cyclone then progressed southeastward along the Adriatic.

Sea-level evolution

On 26 November 1996, at 06:00 UTC, the sea level in Bakar rose to 90 cm above the long-term average. This peak closely aligned with the daily tidal maximum, with the tide contributing 25 cm. In the week preceding the flood, several cyclones crossed the region, generating and repeatedly amplifying Adriatic seiches (T~21.5 hours). Synoptic series show that the final amplification occurred during the first half of 24 November, placing the seiche in a positive phase as the storm surge developed. The flood’s main maximum occurred shortly after the synoptic component peaked at 33 cm.
The remaining sea-level rise resulted from processes acting on other time scales (refer to Figure 1 in the Introduction for detailed explanations): local processes added 7 cm, long-period sea-level variability contributed 5 cm, and mean sea-level changes added 20 cm.

In summary, the flood resulted from positive efects of all sea-level processes, with synoptic component and tide being the most significant.