Hurricane Bob - Meteorological History

Meteorological History

Hurricane Bob originated from the remnants of a frontal trough to the southeast of Bermuda on August 12. The system tracked towards the southwest and later west towards the Bahamas. By August 15, satellite analysis of the system found a weak low pressure area a couple hundred miles east of the Bahamas. Operationally, the system was not declared a tropical depression until 0600 UTC on August 16 after a reconnaissance mission into the storm found a closed circulation and flight level winds of 37 mph (60 km/h). After post-storm analysis, it was determined that the low had developed into a depression around 0000 UTC. Several hours after being designated, the system began to develop convective banding features. Roughly 18 hours after being declared a depression, the National Hurricane Center (NHC) upgraded it to a tropical storm, giving it the name Bob. At this time, Bob was situated roughly 140 mi (225 km) northeast of Nassau, Bahamas. The storm tracked slowly towards the northwest in response to the deep layer mean flow it was embedded within.

A deepening trough over the eastern United States was forecast to turn the storm toward the north on August 16. This turn took place earlier than forecasters anticipated. The storm slowly intensified as convection was displaced from the center of circulation; however, upper-level outflow was well-defined and intensification of the storm was expected as it tracked over the Gulf Stream. Later that day, Bob began to consolidate and a reconnaissance plane recorded hurricane-force winds at 1719 UTC, following this reading, the NHC upgraded the storm to a Category 1 hurricane on the Saffir–Simpson Hurricane Scale. Shortly after, the hurricane began to turn towards the north-northeast in response to a subtropical ridge over the Atlantic and the trough over the southeastern United States.

By August 18, the NHC noted that the hurricane was asymmetrical, having uneven distribution of the wind radii. Later that day, deep convection continued to form and an eye later appeared on satellite imagery. Early the next day, the eye became increasingly defined as the center of Bob passed roughly 35 mi (55 km) from the North Carolina coastline. By 0600 UTC, Hurricane Hunters recorded flight level winds of 140 mph (225 km/h), corresponding to surface winds of 115 mph (185 km/h). At this time, the barometric pressure of the storm also decreased to 950 mbar (hPa; 28.05 inHg), the lowest pressure recorded during the storm. After attaining this intensity, the hurricane tracked quickly northeast at 25 mph (35 km/h), steered by the trough over the southeast United States, an upper-level cutoff low over the Great Lakes Region and the subtropical ridge over the Atlantic.

The track of Bob by August 19 was similar to that of Hurricane Carol in 1954, another major hurricane that impacted New England. Significantly cooler sea surface temperatures in the path of the hurricane resulted in weakening, leading to the eye becoming cloud-filled. Later on August 19, the western portion of the eyewall brushed the eastern tip of Long Island. Around 1800 UTC, the center of Bob made landfall near Newport, Rhode Island with winds of 100 mph (155 km/h), making it a Category 2 hurricane. The storm quickly weakened as it tracked through Rhode Island and Massachusetts before entering the Gulf of Maine. Around 0130 UTC on August 20, the now weakened Tropical Storm Bob made another landfall near Rockport, Maine with winds of 70 mph (110 km/h).

Later that day, Bob had crossed through Maine and part of New Brunswick, Canada and entered the Gulf of St. Lawrence. Around 1800 UTC, the former hurricane transitioned into an extratropical cyclone. Early the next day, the storm passed over northern Newfoundland before re-entering the Atlantic Ocean. Rapidly tracking eastward, the storm briefly weakened to the equivalent of a tropical depression on August 22. After restrengthening to tropical storm-force winds, the remnants of Bob turned towards the southeast and slowed. Once more, the extratropical system weakened to the equivalent of a tropical depression; however, it did not re-intensify. The storm slowly tracked towards the east before dissipating off the coast of Portugal on August 29.