Forecasters at the U.S. National Hurricane Center in Miami said the storm system, which has already caused flooding in Puerto Rico, the Dominican Republic and Haiti, could become Tropical Storm Bonnie later Thursday and reach the Gulf of Mexico by Saturday.
Seas already were choppy in the Gulf Thursday, with waves up to five feet rocking boats as crews prepared to leave if needed. Nonessential vessels like barges and skimmers will likely be sent back to shore, Commander Terri Jordan told the crew of the Coast Guard cutter Decisive at a midmorning briefing.
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She said they were awaiting an evacuation order.
"We are going to be here until everyone is safe and out of here," Jordan said.
Work on plugging the well is at a standstill just days before the expected completion of a relief tunnel to permanently throttle the free-flowing crude.
Worse yet, the government's spill chief said foul weather could require reopening the cap that has contained the oil for nearly a week, allowing oil to gush into the sea again for days while engineers wait out the storm.
"This is necessarily going to be a judgment call," said retired Coast Guard Adm. Thad Allen, who was waiting to see how the storm developed before deciding whether to order any of the ships to leave.
Doug Suttles, BP's chief operating officer, said Thursday afternoon no decision had been made on whether to evacuate ships or open the cap.
Crews had planned to spend Wednesday and Thursday reinforcing with cement the last few feet of the relief tunnel that will be used to pump mud into the gusher and kill it once and for all. But BP put the task on hold and instead placed a temporary plug called a storm packer deep inside the tunnel, in case it has to be abandoned until the storm passes.
"What we didn't want to do is be in the middle of an operation and potentially put the relief well at some risk," BP vice president Kent Wells said.
If the work crews are evacuated, it could be two weeks before they can resume the effort to kill the well. That would upset BP's timetable, which called for finishing the relief tunnel by the end of July and plugging the blown-out well by early August.
Scientists have been scrutinizing underwater video and pressure data for days, trying to determine if the capped well is holding tight or in danger of rupturing and causing an even bigger disaster. If the storm prevents BP from monitoring the well, the cap may simply be reopened, allowing oil to spill into the water, Allen said.
BP and government scientists were meeting to discuss whether the cap could be monitored from shore.
As the storm drew closer, boat captains hired by BP for skimming duty were sent home and told they wouldn't be going back out for five or six days, said Tom Ard, president of the Orange Beach Fishing Association in Alabama.
In Florida, crews removed booms intended to protect waterways in the Panhandle from oil. High winds and storm surge could carry the booms into sensitive wetlands.
Also, Shell Oil began evacuating employees out in the Gulf.
Even if the storm does not hit the area directly, it could affect the effort to contain the oil and clean it up. Hurricane Alex stayed 500 miles away last month, yet skimming in Alabama, Mississippi and Florida was curtailed for nearly a week.
The relief tunnel extends about two miles under the seabed. It's now about four feet from the side of the well, although BP still has more than 100 feet to drill diagonally before the tunnel reaches the well. BP plans to insert a final string of casing, or drilling pipe, cement it into place, and give it up to a week to set, before attempting to punch through to the blown-out well and kill it.
BP's broken well spewed somewhere between 94 million and 184 million gallons into the Gulf before the cap was attached. The crisis — the biggest offshore oil spill in U.S. history — unfolded after the BP-leased Deepwater Horizon rig exploded April 20, killing 11 workers.
The cause of the blast is still under investigation, but there have been repeated questions raised by rig workers over the equipment and safety conditions aboard the rig.
The New York Times reported early Thursday that rig workers said in a confidential survey before the April 20 explosion that they were concerned about safety and the condition of some equipment on board.
The Times reported that another report conducted for Transocean by Lloyd's Register Group found that several pieces of equipment — including the rams in the failed blowout preventer on the well head — had not been inspected since 2000, despite guidelines calling for inspection every three to five years. Transocean said most of the equipment was minor and the blowout preventer was inspected by manufacturer guidelines.
"As part of Transocean's unwavering commitment to safety and rigorous maintenance discipline on all our rigs, we proactively commissioned the safety survey and the rig assessment review," Transocean spokesman Lou Colasuonno said in an e-mail early Thursday. "A fair reading of those detailed third-party reviews indicates clearly that while certain areas could be enhanced, overall rig maintenance met or exceeded regulatory and industry standards and the Deepwater Horizon's safety management was strong and a culture of safety was robust on board the rig."
IN PICTURES: The Gulf oil spill's impact on nature