MIAMI -- Subtropical Storm Teresa formed Friday north of Bermuda as Hurricane Sam intensified farther south in the Atlantic.

The U.S. National Hurricane Center said Teresa had maximum sustained winds of 45 mph (75 km/h) with little change in strength expected. The storm was centered about 155 miles (245 kilometres) north of Bermuda and moving northwest about 14 mph (22 km/h).

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

Hurricane Sam's winds increased to near 85 mph (140 km/h) on Friday, and forecasters expected it to intensify quickly, becoming a major hurricane Saturday.

Sam was centered about 1,290 miles (2,075 kilometres) east-southeast of the northern Leeward Islands and was moving west about 12 mph (19 km/h).