Strong winds and waves from Hurricane Erin have battered Nantucket and Martha’s Vineyard as dangerous rip currents continue to threaten from the Carolinas to New England. But the storm is heading farther out to sea and forecasters say the unusually large hurricane will slowly weaken into the weekend. The menacing waves closed beaches from the Carolinas to New York City on Thursday. On North Carolina’s Outer Banks, waves breached dunes in the town of Kill Devil Hills, and water and sand pooled on Highway 12. But the low-lying islands appear to have dodged widespread destruction.