Hurricane Gabrielle (2001) - Meteorological History

Meteorological History

On September 5, a weak low- to mid-level trough was nearly stationary a short distance off the southeastern coastline of the United States. It remained stationary for several days, before developing a low-level circulation over Florida by September 9. The system moved into the Gulf of Mexico, and by September 11, the low and its associated convection were well-organized enough for the National Hurricane Center (NHC) to classify it as Tropical Depression Eight. By that time, the system was located about 170 mi (270 km) west-northwest of Key West, Florida. Located in an environment of weak steering currents, the depression drifted to the west-southwest after forming. Northerly wind shear and the presence of a nearby upper-level low initially prevented further organization, leaving the center of the depression poorly–defined with minimal convection. The depression gradually became better organized while it slowly executed a small counter-clockwise loop. Early on September 12, the system developed increased banding features over the eastern half of its circulation. By early on September 13, the upper level outflow over the depression became much more conducive for intensification, although the circulation remained broad and weak. Shortly thereafter, deep convection developed and persisted near the center, and at 1200 UTC on September 13, the depression intensified into Tropical Storm Gabrielle while located about 200 miles (320 km) southwest of Venice, Florida.

Under the influence of a mid-level trough, Gabrielle accelerated northeastward and quickly intensified, despite increasing amounts of westerly wind shear. Its center reformed several times under the deep convection, and on September 14 Gabrielle made landfall near Venice with winds of 70 mph (110 km/h). At the time, Hurricane Hunters reported gusts to hurricane force, and the National Hurricane Center indicated the possibility that Gabrielle made landfall as a hurricane. Land interaction and vertical wind shear quickly weakened Gabrielle over land; its convection decreased markedly with the strongest remaining convection remaining well to the northeast of the center. The storm reached the Atlantic Ocean with winds of 45 mph (72 km/h) about 18 hours after it made landfall; by that time, one forecaster at the National Hurricane Center remarked that the storm resembled an occluded frontal low, with a large circulation devoid of convection in a non-symmetric wind field. Another forecaster likened the storm to a subtropical cyclone, due to dry air continuing to limit organization.

On September 15, convection gradually developed closer to the center, though operationally forecasters were unsure whether the convection was in association with Gabrielle or to a cold front to its west. A Hurricane Hunters flight into the system reported the center of Gabrielle became elongated, resembling a trough, and one forecaster considered the storm on the verge of becoming an extratropical cyclone. Shortly thereafter, convection increased near the center as the storm became stronger and better organized. Despite strong amounts of wind shear, Gabrielle intensified to attain hurricane status early on September 17 while located about 350 mi (560 km) to the west of Bermuda. Continuing northeastward, the hurricane strengthened slightly further to reach peak winds of 80 mph (130 km/h) about 230 miles (370 km) northwest of Bermuda. Shortly thereafter, a banding eye briefly developed in the center of the convection. Increased wind shear eventually diminished the convection, and Gabrielle weakened to tropical storm status September 18. By early on September 19, wind shear dissipated nearly all of the associated deep convection, and Gabrielle transitioned into an extratropical cyclone about 350 miles (560 km) south of Newfoundland. The extratropical remnant continued to the northeast, passing a short distance southeast of Newfoundland before restrengthening to reach winds of 75 mph (121 km/h). The storm weakened, and on September 21 the extratropical remnant of Gabrielle merged with another extratropical storm over the far northern Atlantic Ocean.