Series of devastating storms batter Italy

By HansPeter Roesli (Switzerland) and Ivan Smiljanic (DHMZ)

The first part of autumn brought repeatedly stormy weather to both the Italian mainland and the big island of Sicily. One of these events hit Sicily and some of the regions in southern Italy between 8 and 10 October.

Driven by a low pressure centre, initially situated over the north African coast, conditionally unstable air released its energy in many severe thunderstorms that caused widespread heavy downpours and flooding in many areas. This can be clearly seen in the Meteosat-9 Airmass RGB composite animation (Figure 2).

The Airmass RGB composite shown here is adjusted for tropical conditions. It is also useful at mid-latitude, as it offers an improved view of deep convection and overshooting tops, compared to the standard Airmass RGB.

After 10 October the disturbances moved on to south-eastern Europe. A striking feature between 11 and 12 October was a back-building thunderstorm. It started at the heel of Italy (Apulia) and then moved over to the Peloponnese.

A few days later, on 14 October, at least five people were reported to have died after another series of storms hit central Italy, causing fatal floods and landslides.

The following day, 15 October, further storms caused more flooding and at least two more people were reported to have died in the southern region of Campania.

A close look at the Meteosat-10 HRV image (Figure 3) and the animation (Figure 4) reveals the two connected mesoscale convective systems that passed over Sicily overnight and into the early morning. It can be seen that the most intense parts of the two systems (yellow to red colour shading in the loop) did not overlap, meaning that intense flash flooding was avoided.

The first system was concentrated to the west, and later to the east part of the island. Using a combination of HRV and infrared standard cloud-top features of the systems can be observed, for instance overshooting tops and gravity waves.

Looking at the whole of Europe on the Meteosat-10 HRV and enhanced IR animation (Figure 5) a convective band connected to a cold front passage can be observed as one of the most dominant features, stretching from north Africa (Tunisia) to a central Europe (Germany). Although this cold front was connected with many convective events and heavy rainfall, the temperature gradient was not very strong.

Additional content

Deadly floods in Italy (NewEurope)
At least four killed as storms lash Italy (Reuters)
Alluvione nel Foggiano, gravi danni per un temporale autorigenerante (Meteo Giornale) (in Italian)