On September 1, the hurricane began to rapidly deepen over warm waters of the Caribbean Sea; by 18:00 Coordinated Universal Time (UTC), it had strengthened to Category 4 intensity. Continuing westward, the storm passed north of Swan Island later that day. Early on September 2, a double eyewall appeared on satellite imagery. Carmen's forward movement gradually slowed as the storm took a west by north direction, and it reached its initial peak intensity with maximum sustained winds of 150 mph (240 km/h), accompanied by a central barometric pressure of 928 mbar (hPa; 27.4 inHg). Atmospheric steering currents became increasingly weaker, and Carmen slowed to a drift. Later on September 2, the hurricane made landfall on the Yucatán Peninsula; its northern jog spared Belize City from a direct hit. The storm's center passed a few miles north of Chetumal, Quintana Roo.