the National Hurricane Center (NHC) identified the system as a developing subtropical low near Apalachee Bay along the northern coast of the Gulf of Mexico. The agency defines a subtropical cyclone as "a non-frontal low pressure system that has characteristics of both tropical and extratropical cyclones." After becoming a subtropical low, the cyclone tracked northeastward through Georgia, before turning eastward and exiting South Carolina into the Atlantic Ocean. Its track was influenced by the western periphery of the subtropical ridge, which is a large belt of high pressure. While moving over land, the cyclone had become better organized, and on August 15 it transitioned into a tropical depression about 70 miles (110 kilometres) southeast of Charleston, South Carolina. The depression strengthened further, and based on reports from the Hurricane Hunters, it intensified into Tropical Storm Charley late on August 15. With a weak ridge to its north, the storm initially tracked slowly eastward just off the coast of North Carolina, before turning to the north-northeast as a trough approached from the west. A broad cyclone, Charley gradually intensified, and a single ring of convection around the center developed into an eyewall. At 1200 UTC on August 17, it attained hurricane status about 13 mi (21 km) off the North Carolina coastline. About two hours later, Hurricane Charley made landfall near Cape Lookout, and it subsequently moved across the eastern portion of the state. Hurricane Charley did not weaken while moving over land; instead, it intensified, attaining peak winds of 80 mph (130 km/h) after emerging into the Atlantic Ocean near the North Carolina–Virginia border. Within 12 hours of reaching peak intensity, however, the hurricane weakened to tropical storm status. The approaching trough, which had previously caused Charley to turn northward, forced the hurricane to accelerate northeastward and later eastward, bringing the storm about 80 mi (130 km) southeast of Nantucket, Massachusetts on August 19. As the trough was not very strong, Charley slowly underwent the process of extratropical transition, unlike other tropical cyclones that complete the transition much quicker with a stronger trough. As a result, the storm maintained hybrid, or subtropical characteristics for several days. By August 21, Charley completed the transition south of Atlantic Canada. After becoming extratropical, Charley re-intensified under baroclinic instability. The resulting storm was a very large and fairly strong gale that gradually moved across the northern Atlantic Ocean. As an extratropical cyclone, Charley attained