forecast valid from 00:00 until 23:00 on Friday 2 August
A frontal system, inserted in an intense western flow present in free atmosphere, will pass during the day tomorrow on the north of Italy determining a full-bodied worsening of the weather, with hail, flooding and gusts of wind.
The deterioration will be divided substantially into two phases.
The first, from night until early afternoon, with prefrontal thunderstorms that will ride the ascending branch of the jet streak (movement from west / south west to east / north east).
The second, from early afternoon until the evening, with frontal thunderstorms that will affect larger areas but which will be less organized.
The most stringent parameters will be localized in the first phase, in fact we estimate, despite the night / morning hours, peaks on the 2100J / kg of Cape (energy available at the convection), shear (variation of direction and intensity of the wind with the altitude) on 20-25m / s and good values of energy helicity that will favor the formation of organized systems and supercells
The frontal phase will instead see a greater entry of cold air at altitude but a simultaneous collapse of parameters such as shear and a drop in the jet.
Multi-cell or Mcs thunderstorms will be favored.
Lombardy, Veneto, Friuli Venezia Giulia, Emilia Romagna and Trentino
Very active prefrontal phase between middle high plains and Alpine area (level 2-3). The thunderstorms will develop over Lombardy in the very early hours of the night, evolving towards Veneto, Trentino and Friuli, resulting organized and with the possibility of long-lasting supercells, especially between Veronese, Vicentino, Padovano, Veneziano, Rodigino and Trevigiano, where, in the morning, it will be established a convergence between Bora and Scirocco.
In fact, despite the night / morning hours, Cape values are estimated at around 2100J / kg, with the possibility of medium to large hailstorms (> 3cm), flooding, with discomfort and gusts of wind.
The frontal phase will instead be more active in the middle low plains (Emilia Romagna and Veneto border).
The entry of cold air at altitude will allow the development of many thunderstorm cells, but the simultaneous collapse of the shear will determine the evolution of multicellular-cluster or Mcs (mesoscale convective system) thunderstorms.
The areas affected by heavy rain, hail and downburst with gusts above 100km / h will be considerable, with probable inconvenience.
Piedmont, Valle d'Aosta and Liguria
Prefrontal phase that will determine some thunderstorms between Alto Piemonte and Valle D'Aosta but rapidly evolving towards the east.
Afternoon frontal phase that will be more active on the mid-low plains, especially between Langhe and Monferrato, where the formation of multicell clusters will be possible.
Despite the level 1 emitted, the very high Cape values (peaks up to 2500J / Kg) make medium-sized hailstorms and wind blows possible.
Possible thundering storms also attenuated along the Ligurian coast, especially in the stretch between Andora and Genoa.
Although not shown on the map, an obligatory citation for the northern area of the Marche bordering Romagna.
Between afternoon and evening he will find himself on the southern edge of the disturbance, thus keeping shear on high values and at the same time a good convergence of winds to the ground.
In this area it will be possible to form one or two supercells, with the possibility of hailstorms.
The member of the storm chasers group ZenaStormChaser from Genoa, Italy. Follow ZenaStormChaser on Facebook, Instagram or Twitter