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© AccuWeather
Unusually high tides filled many streets of Venice Wednesday as atmospheric forces lifted the northern Adriatic Sea.

The official water level in the city reached 56.6 inches (144 cm) above the average, highest of the year. City authorities reckoned that about 60 percent of the city's streets and piazzas were put under water. On Saint Mark's Square, flood waters stood knee deep, forcing tourists to wade or follow raised boardwalks.

The flooding stopped well short of last year's mark of 63 inches, which yielded the city's worst flooding in more than 20 years.

The atmospheric setting that most often leads to tidal flooding in Venice blends low pressure over northern Italy with high pressure over southeastern Europe and the eastern Mediterranean Sea. The result is a gradient in pressure that lifts the level of the northern end of Adriatic Sea. The pressure gradient also drives southerly and southeasterly winds over the open Adriatic, which add to the lift at the northern end of the sea.

The trigger of this latest incident of flooding lay with a storm tracking from Spain to the Alps. More bouts of flooding will take place during the next few days as more low pressure areas will follow this overall track.