In early July 2019 a six-day severe weather outbreak across the entire northern and central Mediterranean region, was especially harsh in Italy and Greece.
By Jose Prieto (EUMETSAT), Sancha Lancaster (Pactum) and Ivan Smiljanic (SCISYS)
During the outbreak of severe convective storms between 6 and 11 July, there were 480 severe weather reports. The outbreak featured huge hail, damaging wind gusts, flash flooding and a number of deaths.
From 3 June the synoptic situation did not change much for the Mediterranean region. The planetary Rossby wave was almost stationary in the region, being elongated in the West-East direction (along the isolines in Figure 2).
Figure 2: Meteosat-11 Airmass RGB with overlapped geopotential (red lines) and isotachs (yellow lines) at 300hPa
With a moist and warm air mass in the south, plus the presence of sporadic short baroclinic waves that introduced additional instability, the area was prone to have convective development throughout the time period.
Figure 3 is an animation of 10.8 µm imagery from Meteosat-11, depicting the intensity on successive days. Although the instability was constantly over the region, every day shows different areas for the developments, with a preference for the Gulf of Venice.
Figure 3: Meteosat-11 10.8 µm channel animation, 7 July 12:00 UTC–11 July 00:00 UTC
Based on the frequent scan at five minute intervals, the enhanced HRV imagery, supplemented by standard channels in the short IR band to add colour (Figure 4), shows the upper structure of the storms on 9 July, with the usual features of intense convection — overshooting tops, jumping cirrus and anvil — feeding humidity into the lower stratosphere. Note: Flickering due to gain changes to correct for decreasing illumination.
Figure 4: Meteosat-10 Rapid Scan animation, 9 July 09:00–16:30 UTC
In Italy the storms started in the north-east on 7 July and Italy's Civil Protection Department warned of thunderstorms and strong winds in the regions of Piedmont, Lombardy, Trentino-South Tyrol, Veneto, Emilia-Romagna, Tuscany and Marche.
An extremely severe thunderstorm hit Pescara (Abruzzo, central Italy) in the afternoon of 10 July, with very large hailstones, up to 15 cm in diameter, severe winds and intense flash floods.
- In Venice violent winds almost drove a cruise liner to swerve into a dock.
- Eighteen people were reported to have been injured by the huge hailstones in Pescara.
- Beachgoers at Milano Marittima and Cervia had to flee after a violent tornado that hit the whole area .
Also on 10 July a violent storm swept across a region of northern Greece (Figure 5). Gale-force winds, heavy rain and hailstorms lashed Halkidiki, near the city of Thessaloniki and a state of emergency was declared. At least seven people were killed (see related content below) and dozens more injured.
Figure 5: Meteosat-11 animation channel 10.8 µm, 10 July 00:00–11 July 07:45 UTC