Gustav moved erratically to the west-northwest toward the North Carolina-South Carolina border over the next two days, it slowly strengthened, acquiring more tropical characteristics. On September 10, a poorly organized band of stronger winds developed around the center, and Gustav was designated a fully tropical storm[4] shortly before turning toward the north and brushing Cape Hatteras, then accelerating toward the northeast and away from the coast.[2] On September 11, while under the influence of a non-tropical system over New England, Gustav quickly strengthened into a hurricane, in a process similar to the intensification of Hurricane Michael in 2000.[2] Gustav reached its peak intensity of 100 mph (160 km/h) later that day.[2]