Severe thunderstorms with torrential rainfall and extremely severe straight line winds, possibly also tornadic, hit numerous sea resorts along the NE coast of the Adriatic sea in Slovenia and Croatia last Wednesday (June 28).

A particularly volatile severe weather setup established over the northern Adriatic region on June 28, producing severe thunderstorms in parts of the eastern Po plain and particularly along the northeastern coast of the Adriatic sea in Slovenia and Croatia. Numerous popular sea resorts were hit with local flash flooding and intense straight line winds, knocking over trees on cars and campers, destroying traffic signs and boards as well as damaging roofs on numerous buildings.

A strong squall line formed and crossed the Adriatic sea, hitting the eastern coast. Several embedded supercells were evident on radar. A particularly intense isolated HP supercell hit the area near Umag, NW Istra (NW Croatia). Several storm chasers and spotters intercepted the storm. Intense winds in excess of 150 km/h, and likely in excess of 170 km/h were recorded. The thunderstorm caused major damage in Umag, Dajla and the immediate vicinity. The HP supercell evolved into a bow echo and derecho, rapidly moving across N Istra and SW Slovenia. Winds gusting up to 150 km/h were recorded by the ARSO weather station on Slavnik (1027 m, SW Slovenia).

Severe HP supercell approaching the coast in Dajla, Istra. Photo: Matej Štegar.

Approaching HP supercell just outside Dajla, Istra. Note the textbook structure, complete with a massive inflow tail. Photo: Jure Atanackov.

Severe HP supercell on video, Dajla, Istra. Video: Matej Štegar.

Severe wind damage in Umag, Istra, produced by the HP supercell. Photos: Dina Jerman / IstraMet.

Approaching severe squall line over the northern Adriatic towards the coast of Slovenia (Izola in the foreground). Photo: Igor Škof / Neurje.Si

Gust front and shelf cloud over Vrbje pri Žalcu, CNTRL Slovenia. Photo: Sergej Fpr / Neurje.Si

Severe (straight line) wind damage reported in Ankaran, W Slovenia. Photo: Tjaša Žonta / Neurje.Si

Severe wind damage reported in Dajla, Istra, Croatia. Photo: Saša Budija / Istramet

Severe wind damage reported in Novigrad, Istra, Croatia. Photo: Istramet

Severe wind damage reported in Mareda, Istra, Croatia. Photo: Istramet