Atlantic tropical cyclone activity (4:43 am EDT, 19 Aug 2009)U.S. weather forecasters say Hurricane Bill has grown into a powerful storm as it swirls in the open Atlantic - and could become stronger, possibly threatening easternmost Canada next week.

The National Hurricane Center in Miami says in its latest report Wednesday that the storm's winds have increased to 215 kilometers per hour. Bill is about 1,565 kilometers south-southeast of Bermuda and moving to the northwest.

Forecasters expect the hurricane to pass well north of the Leeward Islands, but have warned the storm will produce large ocean swells that will impact the islands of the northeast Caribbean in the next day or two. Large swells are also expected to affect Bermuda and portions of the U.S. east coast on Friday and Saturday.

Hurricane Bill was upgraded Wednesday to a Category Four storm based on the Saffir-Simpson scale of one to five of hurricane intensity.

Bill is the first hurricane of this year's Atlantic season.

 Some information for this report provided by AP and Reuters.