Hurricane Kirk strengthens into Category 3 storm in the Atlantic, expected to grow rapidly

Hurricane Kirk strengthened Wednesday into a Category 3 storm in the Atlantic Ocean and was expected to grow rapidly into a major hurricane, forecasters said.

There were no coastal watches or warnings in effect, and the storm system was not yet deemed a threat to land. But forecaster warned Thursday that "large swells" could reach the U.S. East Coast by Sunday.

Kirk reached Category 3 status on Wednesday, the Miami-based U.S. National Hurricane Center said. The storm was about 1,150 miles east-northeast of the Lesser Antilles with maximum sustained winds of 120 mph.