MELBOURNE, AUSTRALIA — Australian authorities urged people in dozens of rural communities on Thursday to leave home “immediately” to escape an out-of-control bushfire tearing through a national park. About 600 firefighters were battling the blaze in the Grampians National Park, 240 kilometers west of the city of Melbourne, a Victoria state emergency services spokesperson said. The blaze has persisted for more than a week in hot, windy conditions, scorching 55,000 hectares — about one-third of the park — so far without causing deaths or destroying homes. State emergency services warned residents to leave home immediately in more than two dozen