Tropical storm Ida has gained strength in the Atlantic and is expected to grow to hurricane force but too far at sea to pose a threat to land, US weather forecasters said Monday.

Ida's center was 1,035 miles (1,670 kilometers) east of the Leward Islands in the Caribbean, the National Hurricane Center said in its 0900 GMT bulletin.

Moving in a northerly direction with 50 miles (85 kilometer) an hour winds, the storm could reach hurricane strength by the end of the week on a track far from populated areas.

Ida is the ninth named storm of the Atlantic hurricane season, which began in June and ends in November.

So far this season only two storms have become hurricanes, but the most destructive -- tropical storm Erika -- left about 30 dead in the tiny island of Dominica.

September is typically the peak of the hurricane season.

The National Oceanographic and Atmospheric Administration had predicted a less active hurricane season than usual because of the El Nino phenomenon, which inhibits storm formation.