While tracking east of Turks and Caicos Islands on September 11, Hortense became a Category 2 hurricane and then to a Category 3 hurricane by early on the following day. Continuing to intensify, Hortense reached Category 4 intensity on September 12. Around that time, a developing trough centered over the Eastern United States caused the storm to curve almost due northward and accelerate. At 0000 UTC on September 13, Hortense attained its peak intensity with a maximum sustained wind speed of 140 mph (220 km/h) and a minimum barometric pressure of .