The Canadian Hurricane Centre said Thursday it expects Arthur to be a strong post-tropical storm with sustained winds of 65 kilometres an hour and gusts reaching 90 km/h over exposed areas.
It was classified as hurricane earlier Thursday in the United States, where it reached Category 2 status. That means a minimum wind speed of 154 km/h, while a Category 1 storm starts at 119 km/h.
Meteorologist Bob Robichaud said that even with the expected weakening of the system as it moves north, it could pack strong winds when it arrives late Friday or early Saturday morning.
"We're still looking right now at a tropical storm arriving, but very, very close to hurricane strength," he said. "So yes, this is something we're watching quite closely."
By late Thursday, the hurricane centre had issued a tropical storm watch for all of Nova Scotia, Prince Edward Island and southern and eastern New Brunswick.
"By nature, a tropical storm also implies the threat of local flooding from heavy rainfall," Environment Canada said in its bulletin.
Robichaud said Nova Scotia will experience the strongest winds while New Brunswick could see the most rainfall, adding that it's still too early to determine where Arthur could make landfall. The latest predicted storm track from the centre had Arthur sweeping across much of mainland Nova Scotia before heading to Newfoundland.
Forecasters are watching to see how the storm interacts with a trough of low pressure that could indicate how much rain it will bring, but say up to 100 millimetres could fall in parts of New Brunswick.
"In terms of the worst wind, it looks like Nova Scotia and in terms of the worst rain it looks like New Brunswick," said Robichaud.
He said the hurricane centre will have a better handle on potential storm surge Friday afternoon, but cautions that there could be higher water levels along the Atlantic coast and the Northumberland Strait.
Arthur made landfall late Thursday in North Carolina, Cape Lookout and Beaufort. Thousands of vacationers and residents celebrating Independence Day had left parts of the state's popular but flood-prone Outer Banks. Much of the North Carolina coast was under a hurricane warning as the National Hurricane Center in the U.S. predicted Arthur would bring winds of up to 136 km/h to the state's coastline.
Farther north in Boston, one of America's signature Fourth of July events, the annual Boston Pops outdoor concert and fireworks show, was moved up a day because of potential heavy rain ahead of the hurricane.
Arthur, the first named storm of the Atlantic season, prompted a hurricane warning for much of the North Carolina coast. Tropical storm warnings were in effect for coastal areas in South Carolina and Virginia.
Forecasters expect Arthur to be a Category 2 storm and pass over or near the North Carolina's Banks — 320-kilometre string of narrow barrier islands with about 57,000 permanent residents — early Friday, bringing rain, heavy winds, storm surge and dangerous rip tides.
Gov. Pat McCrory warned vacationers along the coast not to risk their safety by trying to salvage their picnics, barbecues and pre-paid beach cottage vacations.
"Don't put your stupid hat on," McCrory said.
On the Outer Banks' Ocracoke Island, accessible only by ferry, a voluntary evacuation was underway. A mandatory evacuation for nearby Hatteras Island visitors began Thursday morning.
Outer Banks residents and out-of-town visitors who fail to evacuate ahead of the hurricane's expected arrival should prepare for possibly getting stuck for several days without food, water or power, forecaster Stacy Stewart of the National Hurricane Center said Thursday.
Other areas of the Outer Banks were taking a cautious yet optimistic approach: No evacuations had been ordered for areas north of Hatteras, including the popular town of Kill Devil Hills, which was the site of the Wright brothers' first controlled, powered airplane flights in 1903.
If Arthur makes landfall in the U.S. on Friday, it would be the first hurricane to do so on July Fourth, according to National Hurricane Center research that goes back to the 1850s.
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