# Innovative Integration of Severe Weather Forecasts into an Extended Arrival Manager
## 5 Case Studies
### Synoptic Analysis  
On 11 May 2019, the Po Valley was affected by strong convective activity that caused economic damage and seriously injured a person in the Lombardy region. The synoptic scenario at 500 hPa was characterized by a stretched trough extending from northern Europe to the Mediterranean basin. In the afternoon hours, the cold air mass at 500 hPa reached the Po Valley with values around \(-26\)\({}^{\circ}\)C and the winds consequently shifted to the northwest [46]. On the other hand, the strong south-westerly flow at low levels moved a large amount of water vapor from the Ligurian Sea to the inland, thus increasing convective instability. These meteorological factors produced favorable conditions for the triggering of convective cells over northern Italy. In this context, a squall line hit MXP, producing intense precipitation and a large amount of hail on aprons and runways. The intense thunderstorm also caused several floods in the city of Milan, where some underpasses and metro stations were closed. Instead, the strong downburst winds caused the falling of trees and billboards that required the intervention of firefighters. On 7 July 2019, the Po Valley was affected by precipitation with a prevalent character of thunderstorms, which was locally very intense and associated in various cases with hail and strong gusts of wind. From a synoptic point of view, in the north of Italy, an anticyclonic field of subtropical nature was retreating towards central-southern Italy under the pressure of more unstable North Atlantic currents at high altitude (Figure 8, left panel). The huge energy reservoir in the lower layers of the atmosphere (humid heat conditions) that had accumulated in the previous days favored the triggering of the first thunderstorms over the Alps as early as midday of 7 July 2019. The intense westerlies moved the first storms towards the plain around 13:00 UTC, but a second group of organized cells hit the central and eastern Po Valley between the late afternoon and evening, producing various forms of damage: numerous garages, basements, roads, and underpasses were flooded, and some buildings were evacuated. On 6 August 2019, an anticyclone circulation characterized the synoptic scenario over the Mediterranean basin and ensured atmospherically stable conditions and sunny weather over the southern regions of the Italian peninsula (Figure 8, right panel). On the other hand, a deep trough located over the British Isles affected central Europe by touching the Alpine chain during the evening and causing a worsening of the weather conditions over the pre-Alps. In this area, the presence of cold air at 500 hPa, with values around \(-13\)\({}^{\circ}\)C, increased the instability of the air column, thus promoting the development of convective cells. In addition, the high values of specific humidity, namely the content of water vapor, at 850 and 950 hPa, in combination with wind shear conditions, easterly wind at 950 hPa, and souherly wind at 850 hPa, produced a very unstable environment. From the early evening, some convective cells affected the Bergamo and Milan provinces with moderate rainfall. Later, the passage of moisture advection over the Alps between 18:00 UTC and 00:00 UTC provided further energy for the convection. Consequently, a more intense convective storm hit the central sector of the Po Valley and produced heavy precipitation, strong wind gusts, and small hail. Traffic Analysis: Historical Traffic under Adverse Weather Conditions at Milano Malpensa and Bergamo Airports  
In order to evaluate the influence of adverse weather conditions on air traffic in the extended TMA around MXP and BGY, located at ca. 77 km distance from each other, FlightRadar24 datasets from three different selected days with severe events--11 May 2019, 7 July 2019, and 6 August 2019--were analyzed.