Status: Finalised Material Material from: Linus, Ivan, Tim ...
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Discussed in the following Daily reports:
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In the end of October severe weather hit different parts of Italy, Austria and France, with casualties. On 29 October a cyclone brought a storm surge to Venice and extreme rainfall and precipitation over the southern Alps. Extreme winds were also registered in several countries. In parts of Italy a complete shutdown of public services was triggered by issue of a red warning related to the storm.
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.
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- Extreme rainfall captured from 7 days before (22 October) and with high confidence from 24 October. However external reports provided to ECMWF indicate that HRES shorter range forecast over parts Italy were unsatisfactory - totals were too large.
- Though not discussed directly above, it is clear from separate feedback that IFS handling details of the strong winds and the very rapid deepening of the low centre were not handled particularly well by the IFS. It seems that with regard to these details this was a low predictability case where very high resolution was critical for capturing the full intensity ferocity of the low and the the full strength of the associated winds.