Tropical Storm Lee (2011)

The cyclogenesis of was complicated, extending over several days in late July. An easterly tropical wave—an equatorward trough of low pressure moving generally westward—exited the west African coast in the fourth week of July, at which point it became largely embedded within the monsoon trough. Oriented north to south, the wave supported little to no precipitation for a day or two as it traversed the open Atlantic. A weak low pressure circulation center developed along the southern periphery by July 28, and over time clusters of moderate, albeit isolated convection increased around the broad wave axis. By that time, atmospheric conditions favored development into a tropical cyclone; an anticyclonic circulation soon formed over the system, creating a supportive upper-level environment. It accordingly became better defined over the next couple of days, retaining low surface pressure as well as concentrated showers and thunderstorms. Following a retrace toward the west-northwest, the system posed an increased threat to nearby land that became relative to higher chances of development, with several forecast models projecting a path directly into the northeastern Caribbean.

During the morning of July 31, the large low markedly gained in organization, and the National Hurricane Center (NHC) noted it was close to becoming a tropical depression. Later that day, however, the mean low-pressure envelope became increasingly elongated, with its westernmost component separating into a tropical wave ahead. Albeit short-lived, this new disturbance featured widely scattered convection, with rainbands briefly impacting the Lesser Antilles. Meanwhile, an Air Force unit had been investigating the area, though communication errors with the aircraft limited sufficient data reception. Despite this shortcoming, separate surface analysis and buoy observations indicated the disturbance lacked a closed circulation at the surface; as such, it did not yet meet the criteria for tropical cyclone classification.