Sept. 17 (UPI) -- Tropical Storm Gabrielle formed Wednesday morning over the open Atlantic Ocean and is forecast to strengthen to hurricane force over the weekend, the National Hurricane Center said. The eye of the storm was about 990 miles east of the northern Leeward Islands, the NHC said in its 5 p.m. EST update . Gabrielle had maximum sustained winds of 50 mph and was moving northwest at 14 mph. "A northwest or west-northwest motion is expected to continue over the next few days," the