Tropical Storm Isaac altered its course on Friday and could move closer to the central Gulf of Mexico (GOM) by Monday and Tuesday than previously expected -- and have grown to hurricane status by then -- prompting some companies to suspend drilling operations and evacuate workers from some platforms.

At midday Friday Royal Dutch Shell plc's U.S. operation was preparing for evacuations of nonessential personnel in the eastern and central GOM.

"These personnel are not essential to core producing and drilling operations and will not be able to perform their normal work functions during the passing storm conditions," Shell said. "Drilling operations have been suspended on some eastern and central assets. No production has been impacted."

At about the same time, BP plc said it was shutting production and evacuating all workers from its Thunder Horse oil and gas platform in the Mississippi Canyon area south of Louisiana, and evacuating nonessential workers from the Na Kika, Horn Mountain and Marlin platforms, according to a Reuter's report. Nearly 300 people work on Thunder Horse, which is the largest deepwater production unit in the world, with capacity to process up to 200 MMcf/d of gas and 250,000 b/d of oil.

Chevron began evacuating nonessential personnel from some of its offshore facilities in the Gulf Friday afternoon. "Production has not been affected," Chevron said. "At our onshore facilities, we are following our storm preparedness procedures and paying close attention to the track and forecast of the storm."

Apache Corp. said it was evacuating nonessential personnel in the eastern GOM "as a precautionary measure."

Anadarko Petroleum Corp. said it was monitoring conditions and was "prepared to safely remove our workers and shut in production to protect the environment if Tropical Storm Isaac begins to track toward our facilities."

The center of Tropical Storm Isaac, the ninth named storm of the 2012 hurricane season, was located about 160 miles south-southeast of Port Au Prince, Haiti, on Friday afternoon and was moving northwest at about 16 mph, according to the National Hurricane Center (NHC). Isaac had maximum sustained winds of 65 mph and, while it was expected to weaken somewhat as it crossed Haiti and Southeastern Cuba, could become stronger again once it heads back out to sea.

NHC's five-day forecast cone predicts the center of the storm reaching the southeastern GOM late Sunday and making landfall near Pensacola, FL, as early as Tuesday. A hurricane watch was in effect in Haiti, and tropical storm watches and warnings were in effect across the region, including Florida's east coast south of Jupiter Inlet, Florida's west coast south of Bonita Beach, the Florida Keys, the Dominican Republic and portions of Cuba, Jamaica, the Bahamas.

Among the events potentially threatened by Isaac is the Republican National Convention, which is scheduled to be held in Tampa, FL, beginning Monday through Thursday (Aug. 27-30).

NHC was also tracking Joyce, which was a tropical storm on Thursday (see Daily GPI, Aug. 24) before degenerating into a remnant low more than 1,000 miles east of the Leeward Islands on Friday. The system wasn't expected to intensify and "could degenerate into a trough at any time," NHC said.

The 2012 Atlantic hurricane season, which has so far been relatively mild, may be about to intensify, forecasters at Weather Services International (WSI) said (see Daily GPI, Aug. 22). WSI, the National Oceanic and Atmospheric Administration and forecasters at Colorado State University have recently nudged their tropical storm forecasters slightly higher from their original forecasts (see Daily GPI, Aug. 10; Aug. 7).

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