(Reuters) - U.S. offshore oil producers were taking initial steps ahead of a storm predicted to become a hurricane in the middle of the week, evacuating non-essential staff from Gulf of Mexico production platforms.

The U.S. National Hurricane Center said that the potential tropical cyclone system Nine near the western tip of Cuba was expected to develop into a hurricane on Wednesday as it moves across the eastern Gulf of Mexico.

It could also turn into a major hurricane when it reaches the northeastern Gulf Coast on Thursday, including the Florida Panhandle and portions of the Florida west coast, with "risk of life-threatening storm surge and damaging hurricane-force winds."

Storm path attribution: LSEG

Chevron ( CVX ) said it was beginning evacuations of non-essential staff from certain Gulf of Mexico facilities.

Meanwhile, Shell said on Sunday it would shut production at its Stones and Appomattox facilities in the Gulf of Mexico as a precautionary measure, along with evacuating non-essential staff from its assets in the Mars Corridor.

Both companies said that these decisions had not yet impacted their production.

The next name on the list of named storms is Helene, and according to private weather forecaster AccuWeather, it could make landfall as a Category 3 hurricane and potentially strengthen into a Category 4.

(This story has been refiled to drop the reference to 'shutting output' in the headline)