Updated

Tropical Storm Isaac formed Thursday in the central Atlantic, but was not expected to become a hurricane or directly threaten land, forecasters said.

At 11 a.m. EDT, the ninth named storm of the Atlantic hurricane season had top sustained winds near 40 mph, 1 mph above the minimum to be a tropical storm. Its center was located about 665 miles east-southeast of Bermuda and moving toward the northwest near 8 mph.

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The storm was expected to move north and then northeast in the open Atlantic, with an area of low-pressure blocking it from nearing the United States, National Hurricane Center forecasters said.

Isaac should stay to the east of Bermuda and the Canadian Maritimes and Newfoundland, said hurricane specialist Eric Blake. But those areas in eastern Canada could feel the outer reaches of the storm sometime Monday or Tuesday. It was expected to strengthen slightly before then, he said.

Isaac formed from a depression that developed Wednesday.

The Atlantic hurricane season began June 1 and ends Nov. 30. September is traditionally one of the busiest months of the season.