Tropical Storm Katia strengthened into a hurricane over the Atlantic Wednesday, while another mass of thunderstorms that could become a named storm this week triggered evacuations of some oil workers from the Gulf of Mexico.

Katia had sustained winds of 75 miles per hour and was the second hurricane of the June-through-November Atlantic hurricane season, the U.S. National Hurricane Center said.

The Miami-based center said Katia was forecast to become a major hurricane with winds over 111 mph by the weekend, but it was too early to tell whether it would threaten land days after Hurricane Island caused major damage up and down the U.S. East Coast.

At 11 p.m. EDT (0300 GMT Thursday), Katia was about 1,165 miles east of the Caribbean's Leeward Islands. It was moving rapidly west-northwest and was forecast to turn northwest in a few days on a course that would keep it away from the Caribbean islands.

Long-range computer models, which can be off by hundreds of miles, show Katia nearing the mid-Atlantic island of Bermuda in about a week. Several models turned it north, away from the East Coast.

The Atlantic hurricane season typically brings 11 or 12 named storms. Katia is already the 11th, and with half of the season still ahead, it is shaping up to be the unusually busy year that was predicted.

Energy companies with oil and natural gas operations in the Gulf of Mexico were keeping watch on a mass of thunderstorms over the northwest Caribbean Sea and eastern Gulf.

In an advisory issued late Wednesday, the hurricane center said the disturbed weather system had a high chance of developing into a tropical cyclone in the next two days.

BP on Wednesday became the first major oil producer to say it was already evacuating some workers from offshore platforms in the Gulf because of the weather system, which will be dubbed Lee if it becomes a named storm.

Anadarko Petroleum Corp said later it was also evacuating non-essential workers from some Gulf platforms and Royal Dutch Shell said it was preparing for some evacuations as well.

Interests along the entire northern Gulf of Mexico coast should monitor the progress of this disturbance, the hurricane center said.

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