The depression continued to organize as it turned westward, and late on September 16 the system intensified into Tropical Storm Fifi while just south of Jamaica. As it moved due west, the storm intensified, attaining hurricane status roughly 24 hours after being named following the formation of an eyewall feature. At that time, the storm was asymmetrical, with gale-force winds extending up to 100 mi (155 km) to the north and up to 50 mi (85 km) to the south. The storm turned slightly southwestward, and by September 18, Fifi reached its peak intensity with maximum sustained winds of 110 mph (175 km/h) and a barometric pressure of 971 mbar (hPa; 28.67 inHg). This made Fifi a high-end Category 2 hurricane on the Saffir–Simpson hurricane scale, which had been adopted the previous year. Around this time, the hurricane had nearly doubled in size, with a gale diameter now covering an area 300 mi (485 km) across.