After entering the southern Gulf of Mexico, Hurricane Ivan weakened to Category 4 status by 0600 UTC on September 14. As it slowly turned to the north, southwesterly flow from a large trough over the central United States increased wind shear over the hurricane. An eyewall replacement cycle, along with dry air and restricted outflow, contributed to the weakening. By late on September 14 the weakening trend ceased as the eyewall became better defined, and Ivan was expected to restrengthen a little bit over an area of warmer water temperatures. The eye diameter expanded to 60 miles (95 km/h), though concurrently westerly wind shear and dry continued to increase. As Ivan approached the Gulf Coast of the United States, Hurricane Hunters reported erosion of the southern portion of the eyewall, and cooler waters just offshore contributed to further weakening. At around 0650 UTC on September 16, Hurricane Ivan made landfall just west of Gulf Shores, Alabama, with winds of 120 mph (195 km/h); the strongest winds occurred over a narrow area near the southern Alabama and western Florida border.