The National Hurricane Center said in an advisory statement early Thursday morning that Isaac was continuing to weaken slowly over land but was still producing heavy rains and severe weather, while water levels remain high along the northern Gulf Coast.
The NHC reported that at 4 a.m. Central Daylight Time maximum sustained winds had decreased to near 45 mph while the strongest winds were primarily occurring over water or near the coast.
Earlier, the NHC said that a tropical storm warning that was in place for Isaac east of the Mississippi-Alabama border had been discontinued, though the warning is still in effect for Cameron, Louisiana.
Isaac, which is moving inland through Louisiana, is expected to hit Arkansas by early Friday. But it is forecast to weaken steadily over the next two days and would become a tropical depression by Thursday night, according to the NHC.
Although Isaac is no longer a hurricane, the NHC cautioned that life-threatening hazards such as storm surges, inland flooding and tornadoes are still occurring.
Chevron Corporation confirmed in a statement late Wednesday that it had safely evacuated all personnel from its operations in the Gulf of Mexico as well as shutting in related production, while also securing its onshore facilities. Chevron added that its Pascagoula Refinery in Jackson County, Mississippi, was running at a reduced rate for precautionary reasons only.
Earlier on Wednesday Shell said that it expected to begin flyover inspections of its assets on Thursday as weather conditions improve, before redeploying staff on Friday, while BP said it was keeping a close eye on the storm.
Meanwhile, there are fears that Isaac could have stirred up oil left over from 2010's Deepwater Horizon disaster. Garret Graves, chairman of Louisiana's Coastal Protection and Restoration Authority, was reported by the Huffington Post to have warned that up to one million barrels of oil is estimated to remain in the GoM because BP has failed to clean it all up.