Hurricane Sam strengthened into a Category 3 hurricane in the Atlantic Ocean on Saturday and is expected to strengthen even more as the weekend progresses.

No coastal watches or warnings were in effect for Sam, which was about 1,095 miles (1,760 kilometers) east-southeast of the northern Leeward Islands in the Caribbean Sea early Saturday. It was moving west-northwest at 10 mph (16 kph).

The U.S. National Hurricane Center in Miami said Sam had maximum sustained winds of 120 mph (195 kph). It's expected to become a Category 4 hurricane Sunday with winds of 140 mph (225 kph).

Meanwhile, Subtropical Storm Teresa formed Friday north of Bermuda. Forecasters said Teresa had maximum sustained winds of 35 mph (55 kph) with little change in strength expected. The storm was centered about 140 miles (230 kilometers) north-northwest of Bermuda.

Forecasters noted that Teresa will likely be the ninth "shortie" of the hurricane season -- systems that are short-lived and relatively weak.