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In the end of October severe weather hit different parts of Italy. On 29 October a cyclone brought a storm surge to Venice and extreme rainfall and precipitation over the southern Alps.
Storm surge generated as a result of the explosive cyclogenesis over the western Mediterranean affected Venice causing massive flooding. While floods of this sort are relatively common in Venice, this time the water levels were 1.54 m above the reference level which ordered this storm as the 4th most intense one in history. The meteorological contribution to this level was more than 1.5 m. In this case the peak intensity of the storm coincided with the astronomical tidal minimum. If this had happened several hours earlier or later, it could have been the record flood. Luigi Cavaleri from Instituto di Scienze Marine, also shared with us that significant wave height (SWH) reached 6 m at their oceanographic tower in the northern Adriatic sea. In a similar storm of 22 Dec 1979 (ranked as 2nd in history) crests reached 9 m above the sea surface. The maximum of SWH was in the late afternoon and evening hours (at about 18 UTC) during the tidal minimum and later on the waves quickly diminished in height.
2. Description of the event
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3.1 Data assimilation
3.2 HRES
The plots below show 24-hour accumulated precipitation 29 October 06UTC to 30 October 06UTC in observations (first plot) and forecasts with different initial times. Already the forecast 5-days before the event (second last plot) had a similar precipitation pattern as the last forecast before the event (second panel). All forecasts underestimated the maximum over the southern Alps by ~half.
(Add precipitation plots)
The plots below show forecasts of 24-hour maximum wind gusts valid 29 October (we are missing wind gusts in synop observations from Italy).
3.3 ENS
The plots below show EFI and SOT 3-day precipitation (27-29 October).
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