Mesoscale Discussion
Valid: Fri 24 Jul 2020 12:00 to Fri 24 Jul 2020 16:00 UTC
Issued: Fri 24 Jul 2020 11:55
Forecaster: PUCIK

*** Severe, well-organised convective storms capable primarily of (very) large hail and severe wind gusts are expected to develop over the highlighted area in the next couple of hours ***

Satellite and lightning data show convective storms progressing across the Adriatic Sea, as well as several weak cells on the border between Slovenia and Croatia. Cumulus field is deepening both over the Dinaric Alps, as well as the lowlands to the immediate northeast. Surface observations show 2m temperatures ranging from 25 to 30 deg C, combined with dewpoints in between of 17 and 20 deg C. These observations match the model simulations and it is likely that MLCAPE values between 1000 and 2000 J/kg are available over the region. As the mid-tropospheric trough approaches, increase in the deep-layer shear is forecast, reaching around 20 m/s in the 0-6 km layer.

Convective initiation is expected to happen within the next hour or two in two ways:
1. Over the Dinaric Alps with storms spreading over the lowlands with time
2. Along the outflow boundaries from the storms crossing the Adriatic Sea.

High-resolution numerical models simulate development of several supercells over the area that will be capable of large to very large hail. As storm coverage increases, cell mergers may result in development of one or more line segments that will propagate eastwards and will be capable of severe wind gusts.

The largest uncertainty stems from the severe storm that is currently propagating along the eastern Italian coastline with its anvil spreading over the northwestern Croatia and Slovenia. This could affect the degree of upslope circulation and also the subsequent initiation.