WASHINGTON - Hurricane Isabel was churning yesterday on course for a potentially destructive landfall along the Atlantic seaboard, as U.S. Coast Guard officials repositioned rescue vessels and nervous residents descended on hardware stores and food markets from the Carolinas to Maryland.

Public-safety officials ordered the evacuation of nearly 1,000 residents from an isolated island in North Carolina's Outer Banks, and Virginia's governor declared a state of emergency.

In Chesapeake, Va., a hardware store owner threatened to summon police to quell customers' squabbling over batteries and emergency generators.

In Norfolk, Va., U.S. Navy officials met late into the day, trying to decide whether to send as many as 70 vessels from the Atlantic Fleet out to sea to ride out the storm.

The National Hurricane Center in Miami reported last night that Isabel had weakened slightly to a Category 3 storm as it spun in the Atlantic Ocean, 700 miles south-southeast of Cape Hatteras, N.C., and moving west-northwest at 8 mph.

The storm's mountainous rain clouds stretched hundreds of miles, with sustained raking winds approaching 120 mph. The storm packed violent gusts that had surged as high as 160 mph Sunday.

Forecasters were projecting that Isabel would cross the Outer Banks near Cape Hatteras Thursday afternoon and then bear down on the Chesapeake Bay region.

But they cautioned that the storm's tracking area remained wide and was still capable of major fluctuations - making it difficult to pinpoint Isabel's true path.

In Portsmouth, Va., Coast Guard officials were preparing for the worst.

"We're strongly urging the maritime community to heed the hurricane warnings and seek a safe haven," Coast Guard Petty Officer Tim Pike said.

All six of the fleet's 270-foot-long cutters were shipping out from the Norfolk harbor, Pike said, along with several smaller patrol boats.

The Coast Guard also was trying to decide whether to reposition its air fleet from Elizabeth City, N.C.

A C-130 already had been dispatched out into the Atlantic from the Coast Guard base, flying toward the hurricane and searching for boats that might have missed warnings broadcast all day over maritime radio channels.

"In response to the approach of Hurricane Isabel, severe winds of 74 mph or higher may affect this area," the message said. "Mariners are advised to take prudent action."

On the Outer Banks island of Ocracoke - linked to the mainland only by ferry - 921 residents were ordered to leave at noon yesterday by Hyde County Sheriff L.B. Johnson.

The sheriff said by telephone that he expected residents of the lowlands along the Carolina coast also would be told to head west, away from the open water, today.

"We're evacuating the nursing home," he said. "We're not sure what we're going to do about the prison yet."

Johnson said county emergency officials expected Isabel to "hit around noon Thursday, with winds of around 125 mph when it makes landfall."

As he spoke, county commissioners were meeting to declare a state of emergency.

Virginia Gov. Mark R. Warner did the same yesterday, placing National Guardsmen, state police and road crews on alert.

When Wentz Hardware in Chesapeake opened its doors yesterday morning, there was a jittery crowd outside. Within minutes, said owner Larry Simpson, customers had lugged off four 150-pound generators at $999 apiece and were arguing with each other over shrinking stocks of batteries, plastic stripping, flashlights and tools.

"I had to threaten to call the cops," he said. "Lord, they were hovering like ants!"

Residents hunkering down on the North Carolina coast also were picking store shelves clean.

Angie Brady, a spokeswoman for the Outer Banks Chamber of Commerce in Kill Devil Hills, said "people are getting ready as best as they can," getting in supplies of drinking water and plywood to board up windows.

But she worried that the brutal winds of the storm would prove too harsh for those planning to wait Isabel out.

"We've never had a hurricane hit as directly as this one is predicted, and that's why it's scary," Brady said.

The Los Angeles Times is a Tribune Publishing newspaper.