MIAMI — Starved of its daily dose of crude and under assault by wind, waves, sun, oil-eating bacteria and the largest fleet of oil skimmers ever assembled, the massive blob that stalked the gulf for three months had already been shrinking and scattering for more than a week.
Now, a blustery tropical system could literally blow much of its remnants away, whipping the countless drifting streamers of ooze, mats and balls so far and wide the surface slick could virtually vanish overnight.
But Tropical Depression Bonnie, expected to hit the main spill area this afternoon, also could drive a toxic tide even deeper into the rich and fragile estuaries of coastal Louisiana or perhaps propel tar balls back toward beaches on the Florida Panhandle.
It might even draw suspended oil up from the depths to form new slicks — plumes that scientists at the University of South Florida on Friday definitively traced to BP's blown-out well with chemical fingerprinting.
Experts predict Bonnie could help some spots and hurt others depending on which way the wind blows as the storm races across the gulf.
"In some areas, it may disperse oil. In other zones, it may shove it inland," said Ron Kendall, director of the Institute of Environmental and Human Health at Texas Tech University.
Ships relaying the sights and sounds from BP's broken oil well stood fast Friday as the remnants of the storm blew straight for the spill site, threatening to force a full evacuation that would leave engineers clueless about whether a makeshift cap on the gusher was holding.
Vessels connected to deep-sea robots equipped with cameras and seismic devices would be among the last to flee and would ride out the rough weather if possible, retired Coast Guard Adm. Thad Allen said.
"If conditions allow, they will remain through the passage of the storm," Allen said in New Orleans.
Some of the dozens of vessels working at the well site were leaving Friday evening. By daybreak, all but a handful, including those providing video images, were expected to remain. Allen said individual captains would decide when to leave, based on weather conditions.
The ships holding the robots would be among the first to return if forecasts force them to leave, but they could be gone for up to two days.
The mechanical plug that has mostly contained the oil for eight days will be left closed, Allen said. But if the robots are reeled in, the only way officials will know whether the cap has failed will be if oil pooling on the surface appears in satellite and aerial views — provided the clouds aren't too thick.
Audio surveillance gear left behind could tell BP whether the well is still stable, but scientists won't be able to listen to the recordings until the ships return to the area.
Allen said Friday that he had flown over the area the previous day and "there's not a lot of oil out there."
But he acknowledged the storm could drive much of what is out there onto beaches or into wetlands yet untouched by the spill. He said crews were "prepared to move out and aggressively attack this once the threat is passed through."
With seas up to 10 feet likely to swamp miles of boom set to protect coastal areas, there was little question that portions of low-lying coastal marshes would be inundated.
The federal government's daily shoreline report showed heavy oiling already in some spots at the tip and both sides of the delta, from Barataria Bay to the Chandeleur Islands.
Hurricane Alex, which passed far south of the spill site in June, managed to push oil as far north as Lake Pontchartrain. Bonnie, though less powerful, was tracking dead center toward the Deepwater Horizon site some 50 miles off the delta's tip and pushing an expected storm surge of 2 to 5 feet.
Just how much oil remains in the gulf is uncertain, but the surface slick has visibly shriveled in the eight days since BP finally corralled its raging well.
In the bay area, high humidity and typical afternoon storms are expected after the storm, Bay News 9 meteorologist Mike Clay said. There is a 60 percent chance of rain today.
"It could weaken even more," Clay said of the storm. "It's really very poorly organized."
Katie Sanders, Times staff writer, contributed to this report, which contains information from the Miami Herald and Associated Press.