The storm is moving northeast at about 23 mph.
The threshold for a tropical storm is sustained winds of 39 mph. When those winds reach 74 mph, it becomes a hurricane.
The storm had maximum sustained winds of 40 mph and was centered about 330 miles south of Halifax, Nova Scotia, according to the National Hurricane Center.
The storm was expected to grow stronger but "as a tropical system it has a very short life ahead of it," said James Franklin, a senior hurricane specialist with the Hurricane Center.
There were two previous named storms in 2007: Subtropical Storm Andrea, which formed in May, and Tropical Storm Barry, which formed June 1, the first day of hurricane season.
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