Tropical Storm Dorothy (1970) - Meteorological History

Meteorological History

The origins of Tropical Storm Dorothy were from a tropical wave that moved off the coast of Africa on August 13. It tracked generally westward, developing into a tropical depression on August 17 about 1375 mi (2210 km) east of Tobago in the Lesser Antilles. Two days later, it strengthened into Tropical Storm Dorothy, while located about 500 mi (800 km) east of the Lesser Antilles, with its intensity confirmed by the Hurricane Hunters.

With light vertical wind shear and warm water temperatures, the National Hurricane Center (NHC) remarked on August 19 that "hurricane status would probably be attained this afternoon or tonight." Its track was expected to continue generally west-northwestward, influenced by a ridge near the Bahamas, and within 60 hours Dorothy was forecast to be north or over Puerto Rico. However, a subsequent Hurricane Hunters flight reported a more westerly motion, which would bring its track through the central Lesser Antilles. Tropical Storm Dorothy gradually intensified, reaching peak winds of 70 mph (110 km/h) on August 20 just east-northeast of Barbados. Hurricane Hunters confirmed the intensity, though the flight also reported a weakness of low-level inflow. Despite maintaining winds of just below hurricane-force, there was no evidence of an eyewall on radars as the storm approached the Lesser Antilles. Late on August 20, the storm moved across Martinique into the Caribbean Sea, during which its low-level circulation became disorganized.

As Tropical Storm Dorothy moved further into the Caribbean Sea, it began a gradual weakening trend initiated by a persistent tropical upper tropospheric trough, as well as the presence of strong wind shear and a lack of inflow. Hurricane Hunter flights late on August 21 and early on August 22 failed to locate a closed low-level circulation, and as a result the storm was downgraded to a tropical depression. After another flight into the system could not detect a circulation, the NHC discontinued advisories on Dorothy to the south of Hispaniola late on August 22. Around the same time, thunderstorms increased in association with the cyclone, and forecasters remarked the potential for re-intensification over the western Caribbean Sea. However, the storm became more disorganized, and on August 23 Dorothy degenerated into a tropical wave.