Hurricane Bertha (1990) - Meteorological History

Meteorological History

A cold front moved eastward through the United States in the middle part of July, and reached the East Coast of the United States on July 23. By the following day, a low pressure area developed just southeast of Cape Hatteras, North Carolina ahead of the frontal zone, and quickly formed into a subtropical depression. In association with a nearby upper-level low, the depression tracked quickly southeastward before turning to the southwest. The subtropical depression gradually organized, and satellite classifications began subsequent to merging with a tropical wave on July 25. Convection developed closer to the center of circulation as it gradually decelerated while continuing southwestward and on July 27, the system organized into Tropical Depression Three while located about 335 miles (539.1 km) east of Daytona Beach, Florida.

Upon transitioning into a tropical cyclone, the depression executed an elongated counter-clockwise loop to the northeast. Conditions favored further intensification, and based on ship reports, it is estimated the depression strengthened into Tropical Storm Bertha early on July 28. Bertha quickly strengthened to attain hurricane status early on July 29 about halfway between Cape Canaveral, Florida and Bermuda. The strengthening trend was brief, however, as increased vertical wind shear weakened it back to a tropical storm late on July 29, with the center exposed from the deep convection. Bertha continued slowly northeastward to ridging from the Bermuda high extending westward to the United States.

Operationally, forecasters at the National Hurricane Center speculated whether Bertha was transitioning into a subtropical cyclone, due to its deep convection being located, at times, over 200 miles (321.8 km) from the center. However, the convection progressively returned to the center and by late on July 30, Bertha re-intensified into a hurricane as the convection covered the center, about 415 miles (667.8 km) east of where it first formed. Early on July 31, the hurricane briefly attained peak winds of 80 mph (130 km/h) before weakening and accelerated northeastward as the ridge of high pressure was slowly eroded. Bertha maintained hurricane status as it approached Atlantic Canada, and briefly reached winds of 80 mph (129 km/h) before weakening and making landfall near Sydney, Nova Scotia on August 1 as a 70 mph (113 km/h) tropical storm. The storm was transitioning into an extratropical cyclone while approaching Atlantic Canada, and lost all tropical characteristics shortly after moving ashore. The weakening extratropical remnants of Bertha turned northward into the Gulf of Saint Lawrence and lost its identity shortly thereafter.