Days of torrential rain and snow cover caused severe flooding and fatal landslides in parts of Italy in the first half of November.
04 May 2023
03 November 2014
The Meteosat-10 enhanced infrared animation, 10 November 15:00–23:00 UTC shows rapidly developing convection over northern Italy on the evening of 10 November. In Chiavari two people were killed in landslide caused by the torrential rain. Up to 200mm of rain was reported at places.
On 11 November Lake Maggiore flooded the Italian city of Pallanza after more than 100mm in 24 hours was measured. In Ticino avalanche warnings were in place.
Figure 2 and 3 are showing the average temperature of Meteosat-10's channel IR10.8 spanning the period from 4 November 00:00 UTC to 12 November 23:45 UTC, i.e. the mean cloudiness of those days.
This encompasses the two most intense rain periods with snowfall levels above 2000m, i.e. with negligible rainwater storage as snow. These are reflected in the first two peaks on 6 and 13 November of the water level of Lake Maggiore .
The last peak on 16 November was due to yet more rainfall. This time the snowfall level had fallen below 1500m, resulting in a reduction in the immediate run-off of the rivers flowing into Lake Maggiore.
Figure 2 gives an overview over Europe and shows an elongated cloud band which ran from North Africa across the Alps to the Baltic Sea. This highlights the dominant meteorological pattern at the root of the frequent and intense rainfalls — a persistent elongated trough over western Europe with an embedded frontal zone marked by the cloud band.
Figure 3 gives a close-up view over the Alps. The relatively cloud-free zone, which ran from Central Switzerland to Austria, was due to frequent foehn occurring in the northern alpine valleys.
The relatively cold cloudiness just north of the foehn gap resulted mostly from wave clouds that formed downwind of the Alps.
In contrast to the northern alpine valleys, the southern alpine valleys and northern Italy are barely visible under a moderately cold cloud deck, confirming the observation that during the nine days convective events were very rare and essentially limited to the coastal areas in Liguria.