Hurricane Juan - Meteorological History

Meteorological History

A large tropical wave accompanied by a broad area of low pressure moved off the coast of Africa on September 14, 2003. It initially tracked westward and remained disorganized due to unfavourable upper-level wind shear. On September 20, the convection around the system greatly increased during interaction with the circulation of a large upper-level low, though unfavorable conditions caused the activity to remain disorganized. The system as a whole moved to the northwest around the upper-level low and developed a mid-level circulation. It interacted with a frontal zone, and became better organized on September 23 while located 450 mi (725 km) south of Bermuda. Later that day, a low-level circulation developed within the system, though its involvement with the proximate frontal zone prevented it from being classified a tropical depression. Deep convection increased near the centre on September 24, and the system quickly developed banding features and distinct outflow. Based on the increase in organization, the National Hurricane Center (NHC) classified it as Tropical Depression Fifteen later that day while it was located about 345 miles (555 km) southeast of Bermuda. Operationally, the agency did not initiate storm advisories until 27 hours after the time of its formation determined by post-hurricane season analysis.

Initially, the depression possessed a combination of tropical and subtropical characteristics; it remained attached to a nearby frontal zone, though the organization of the convection and a warm core within the system resulted in classification as a tropical cyclone. Forecasters had predicted the depression would only slowly strengthen and reach a peak intensity of 65 mph (105 km/h). However, the depression steadily organized and had strengthened into Tropical Storm Juan by early September 25. Juan moved northwestward at around 10 mph (16 km/h) in response to a developing subtropical ridge to its east. On September 26, an eye feature developed, and very deep convection increased around the circulation. The cloud pattern continued to consolidate, and Juan attained hurricane status later on September 26 while located 165 mi (270 km) southeast of Bermuda. The hurricane moved into an area of warm waters and light wind shear, allowing for additional strengthening; by September 27, Juan had attained a peak intensity of 105 mph (165 km/h) while located 635 mi (1,020 km) south of Halifax, Nova Scotia. At this peak strength, the eye of the hurricane was distinct and embedded within a well-defined and round central dense overcast.

Hurricane Juan remained at peak intensity for over 24 hours. After moving northwestward for an extended period of time, it turned and accelerated to the north. The eye became less distinct on September 28, and the hurricane weakened slightly. Due to its fast forward motion, Juan had little time to weaken over significantly colder waters before making landfall between Shad Bay and Prospect (near Halifax) on September 29 with winds of 100 mph (160 km/h). It weakened quickly while rapidly moving across the southern Canadian Maritimes and crossing the Nova Scotia peninsula as a hurricane. Juan had diminished to a tropical storm as it moved over Prince Edward Island by early September 29. Later that afternoon, the storm was absorbed by a large extratropical low over the northwestern Gulf of Saint Lawrence.