Mesoscale Discussion
Valid: Sat 23 Aug 2014 14:00 to Sat 23 Aug 2014 18:00 UTC
Issued: Sat 23 Aug 2014 14:32
Forecaster: PISTOTNIK

... Central Italy into S Croatia and Bosnia-Hercegovina ...

Thunderstorm activity has merged into a WSW-ENE oriented line with possibly various embedded supercells. Ahead of this line, dewpoints mostly between 20 and 24°C and temperatures around 28°C are reported along both the Tyrrhenian and Adriatic coasts. This rich moisture is advected onshore with Southwesterly and Easterly winds, respectively. Modifying the 12 UTC Pratica di Mare sounding, it appears likely that more than 2000 J/kg CAPE are available in the onshore flow regime along with deep-layer shear around 25 m/s and veering profiles.
The thunderstorms have a history of producing torrential rain and waterspouts. According to satellite imagery, they are following their own well-established outflow boundary. It is therefore likely that they will continue to propagate to the ESE for some more hours into regions where the forecast models showed little or no precipitation signals. Embedded rotating updrafts may produce several more tornadoes, mostly over water but also possibly a damaging tornado over land (especially along the Italian East coast, where low-level shear and veering are maximized). Besides, a risk of severe wind gusts, large hail and further flash floods persists.
In the evening, the center of the activity will shift towards Dalmatia, while the storms over Italy are expected to gradually decay as they encounter a strengthening cap towards the South.

...N Italy ...

Significant clearing is underway after a morning full of thunderstorms and heavy rain. Latest surface observations show dewpoints still around 17°C and Easterly surface winds. No CAPE was present yet at 12 UTC according to the Cuneo, Milano and Udine soundings. It needs to be awaited if upper-level cooling ahead of the main trough axis and a few hours of sunshine will suffice to enable a few evening storms, which would have a potential to organize very well under increasing vertical wind shear.