Severe thunderstorms accompanied by very large hail hit central Italy on September 5, 2015 prompting officials to declare the highest alert level for the risk of severe weather phenomena.

The hardest hit was the city of Puzzuoli, near Naples, where baseball-sized hail reportedly injured several people and caused extensive damage to the infrastructure.

Large hail hits Puzzuoli, Italy. Image credit: YouReporter.it

According to senior meteorologist for Weather.com, Jonathan Erdman, the storm was brought on by a vigorous southward plunge of the jet stream that carved into western Europe sending a potent upper disturbance into the Italian peninsula.

That instability then charged up thunderstorms over the Mediterranean Sea, which swept into Italy. "The satellite signature was classic for a severe thunderstorm, or cluster of storms," Erdman said.

Featured image: Severe thunderstorm forming over central Italy on September 5, 2015. Image credit: EUMETSAT.