Delta could strengthen into a hurricane, but would remain well clear of land, according to the center's forecasts.

At 2100 GMT it was located 1,850 kilometers (1,150 miles) southwest of the Azores Islands.

Delta is the 25th named storm, including 13 hurricanes, in the current Atlantic hurricane season, which runs from June 1 to November 30.

The previous busiest Atlantic hurricane season on record was in 1933, with 21 storms.