Jonathan Wiggs/Globe Staff
Authorities are closing beaches on the coast of Massachusetts today as heavy surf and rip currents arrive from Hurricane Bill.
All the beaches at the Cape Cod National Seashore have been closed until conditions improve, which probably means at least until Sunday evening, South District Ranger Garrett Moynihan this afternoon.
There are 12- to 15-foot waves at Marconi Beach in Wellfleet. The waves are devouring the sand at the beaches at the park, which stretches along the outer edge of the Cape from Chatham to Provincetown, he said.
The Department of Conservation and Recreation said this evening it was closing beaches in Dartmouth, Westport, Nahant, Hull, Revere, Salisbury, Sandwich, and Winthrop. Officials said Friday that all the beaches on Nantucket and at least one on Martha's Vineyard would be closed from early this morning to 9 a.m. Monday.
The hurricane, advancing north in the Atlantic, is expected to make its closest pass to New England late tonight into tomorrow morning, passing roughly 175 miles south-southeast of Nantucket, according to the National Weather Service office in Taunton.
The strongest effects will be felt on the Cape and islands and the Rhode Island coast, said Kim Buttrick, a weather service meteorologist.
The storm will bring rain, said Buttrick, "but the main effects are going to be for the ocean, in terms of waves, rip currents, and potential erosion along the east and southeastern shores."
The forecasters issued a tropical storm watch for the Cape and islands, and a high surf advisory for the east and southeast coast of the state, warning that powerful swells are already beginning to build and the risk of rip currents will increase this evening. The forecasters also warned people not to venture too close to the water on rocks and seawalls.
State officials urged residents to continue to monitor the progress of the hurricane, saying it would likely have a "serious impact" on coastal communities.
Massachusetts Emergency Management Agency officials said swimmers should stay out of the ocean all along the state's coast, regardless of their abilities, and pleasure boaters should avoid the outer Cape and islands.
"Swimmers should stay out of the water this weekend, and boaters should use extreme caution," Governor Deval Patrick said in a statement.
Seas are expected to reach 14 to 18 feet just south and east of Nantucket tonight and early Sunday.
At Horseneck Beach this afternoon, thousands of beachgoers enjoyed the day but heeded warnings not to go into the water, except for dabbling their toes.
Head lifeguard Bob Fitt said the decision was made at 8 a.m. to ban swimming at the beach, which is known for its strong currents. Parking is free today to make up for beachgoers' disappointment.
Fitt estimated the waves at 3 to 6 feet this afternoon but said officials were expecting 10-foot or higher waves. "This has the potential to be just massive. It really does," he said.
At 5 p.m., the center of the Category 1 hurricane was located about 300 miles south-southeast of Nantucket. The storm was moving north at 24 mph and was expected to gradually turn toward the north-northeast, according to the National Hurricane Center. The maximum sustained winds have declined to 85 mph and the storm is expected to weaken on Sunday.
The weather service also issued small craft advisories for the outer coastal waters and the coastal waters south of Rhode Island.
The forecasters also noted that gusty thunderstorms capable of producing flooding were expected over the interior mainly each afternoon and evening.
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