The Miami-based National Hurricane Center said the low pressure area over the central Gulf and moving northwestward had an 80 per cent chance of becoming a tropical cyclone in the next two days.
Forecasters said the storm’s path was difficult to predict but models increasingly showed the system about 200 miles (321 km) south of Louisiana that could reach the state’s south-central coast by Sunday.
The Gulf, which supplies nearly a third of the US’ oil, is home to operations run by energy giants including BP, Annadarko, Shell, Murphy and Exxon.
So far only a small amount of Gulf output has closed down – 5.7 per cent of oil and 2.4 per cent of natural gas, according to the US Bureau of Ocean Energy Management. But those percentages are likely to rise significantly in coming days as the storm develops.
The storm – which would be named Lee – could spur torrential rains and flooding across the Gulf Coast, but that could bring relief to Texas, which is in the grip of a severe drought.
“We’ve got a huge area of moisture. We’ve got a developing wind field,” National Hurricane Center director Bill Read told reporters in Miami.