HELSINKI—Norwegian experts say an unusually large meteor was visible over large parts of southern Scandinavia and illuminated southeast Norway with a powerful flash of light for a few seconds as many observers were reported to also hear a roaring sound afterward. The Norwegian Meteor Network said that it had analyzed and reviewed several videos of the event Sunday and said the meteor first appeared about 90 kilometers (55 miles) north of the capital, Oslo, and continued its trail in a southwest direction before fragmenting in several flashes of light. “The meteor appeared at 1:08 a.m. on the night of July 25 and was visible for approximately 5 seconds,” said the network said, which had posted a video on the phenomenon on its Twitter site. Sightings of meteors, space rocks that burn brightly after entering the Earth’s atmosphere at high speed, aren’t uncommon over Norway and the Norwegian Meteor Network has …