Tropical Storm Arthur crawled closer to the North Carolina coast on Sunday evening, amid threats of some minor flooding and rough seas as the system moves off the Southeast seaboard.
Arthur formed Saturday in waters off Florida, marking the sixth straight year that a named storm has developed before the official June 1 start of the Atlantic hurricane season.
The US National Hurricane Center in Miami issued a tropical storm warning for North Carolina's Outer Banks on Sunday.
At 8 pm EDT, the storm's center was located about 260 miles (425 kilometers) south-southwest of Cape Hatteras, North Carolina.
Arthur had top sustained winds of 45 mph (75 kph) and was moving to the north-northeast at 9 mph (about 15 kph).
Forecasts projected Arthur would stay well offshore of Florida, Georgia and South Carolina on Sunday before approaching the North Carolina coast, where 1 to three inches of rain is expected through Monday.
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The hurricane center said Arthur is expected to move near or just east of the coast of North Carolina on Monday and they turn away from the East Coast on Monday night and Tuesday.
By Sunday night, the storm's swirling outer rain bands were skirting closer to the coast.
A tropical storm warning was issued for parts of North Carolina's coast, from Surf City to Duck, including Pamlico and Albemarle Sounds.
Michael Lee, a meteorologist with the National Weather Service in Newport, North Carolina, said tropical storm-force winds are possible along the coast, particularly in the Outer Banks.
"Otherwise, it's going to be some heavy rainfall for a large part of eastern North Carolina, Lee said.
But the main threat that we're really trying to get out there is that there is enhanced risk for dangerous rip currents both today and tomorrow. So, any folks who want to try to go to the beach and get in the water, we have a high risk out for most of our beaches.
The weather service said eastern North Carolina should prepare for some localised flooding and dangerous marine conditions along the coast.
Minor inundation from storm surge is possible for very low-lying areas adjacent to the ocean, sounds, and rivers, with overwash of dunes and flooding of properties and roadways possible for locations where dune structures are weak, mainly north of Cape Lookout, the weather service said.
Dangerous coastal surf conditions and rip currents are expected to spread northward from Florida to the mid-Atlantic states during the next few days.
North Carolina Gov. Roy Cooper urged residents along the coast to pay close attention to the storm and don't take chances in dangerous surf.
While there may be a component of warming waters and climate change in other pre-June storms, Arthur is more of a subtropical storm system than a traditional named storm and its water is cooler than what's usually needed for storm formation, said Colorado State University hurricane researcher Phil Klotzbach.
A lot of these out-of-season storms are weak fleeting ones that meteorologists can see now because of satellites and better technology and would have been missed in earlier times, Klotzbach said.
Like most earlier-than-usual storms, Arthur is likely to remain offshore, but could come relatively close to North Carolina's coast Monday, Klotzbach said. Hurricane season officially starts June 1.
Local forecasters in the Bahamas said showers have lingered over the islands of Grand Bahama and Abaco, which are still struggling to recover after being hit by a Category 5 hurricane last year.
However, no flooding has been reported as the depression swirls just northwest of the archipelago and is expected to head into open ocean as it strengthens.
Officials said they were prepared to evacuate patients currently housed in tents in Grand Bahama after Hurricane Dorian damaged the island's hospital, but forecasters said the bulk of thunderstorms are located north and east of the depression and are not expected to affect the region.