Ivan weakened slightly as it moved west-northwest towards Jamaica. As Ivan approached the island late on September 10, it began a westward jog that kept the eye and the strongest winds to the south and west. However, because of its proximity to the Jamaican coast, the island was battered with hurricane-force winds for hours. After passing Cuba, Ivan resumed a more northerly track and regained Category 5 strength. Ivan's strength continued to fluctuate as it moved west on September 11, and the storm attained its highest 1-minute maximum sustained winds of as it passed within of Grand Cayman. Ivan reached its peak strength with a minimum central pressure of on September 12. Ivan passed through the Yucatán Channel late on September 13, while its eyewall affected the westernmost tip of Cuba. Once over the Gulf of Mexico, Ivan weakened slightly to Category 4 strength, which it maintained while approaching the Gulf Coast of the United States. When Ivan entered the Gulf of Mexico, U.S. Naval Research Laboratory ocean-floor pressure sensors detected a freak wave, which was caused by the hurricane. The wave was around high from peak to trough, and around long. Their computer models also indicated that waves may have exceeded 130 feet (40 m) in the eyewall. Just before it made landfall in the United States, Ivan's eyewall weakened considerably, and its southwestern portion almost disappeared. Around 2 a.m. CDT (UTC–5) on September 16, Ivan made landfall on the U.S. mainland in Gulf Shores, Alabama, as a Category 3 hurricane, with 1-minute sustained winds of . Some hurricane information sources put the winds from Hurricane Ivan near (Category 4) upon landfall in Alabama and northwestern Florida. Ivan then continued inland, maintaining hurricane strength until it was over central Alabama. Ivan weakened rapidly that evening and became a tropical depression on the same day, still over Alabama. Ivan lost tropical characteristics on September 18 while crossing Virginia, becoming an extratropical storm. Later that day, the remnant low of Ivan drifted off the U.S. mid-Atlantic coast into the Atlantic Ocean, and the low-pressure disturbance continued to dump rain on the United States. On September 20, Ivan's remnant surface low completed an anticyclonic loop and moved across the Florida peninsula. As it continued westward across the northern Gulf of Mexico, the system reorganized and again took on tropical characteristics on September 22. On September 22, the National Weather Service, "after considerable and sometimes animated in-house discussion [regarding] the demise of Ivan," determined that the low was in fact a result of the remnants of Ivan and thus named it accordingly.