The overland reintensification of Tropical Storm Danny (1997)

Commonly, landfalling tropical cyclones (TCs) either weaken or reintensify as a transitioned extratropical cyclone, often through baroclinic processes. However, there is a potential third option - that the remnants may modestly restrengthen overland as a TC. However, due to the lack of a warm sea surface, this must be accomplished primarily through traditionally extratropical methods of intensification. Hurricane Danny (1997) is one such case.

Hurricane Danny made landfall as a minimal category one hurricane over southern Alabama on 19 July 1997 and then quickly weakened to a tropical depression while drifting northeastward. Upon entering western North Carolina several days later, Danny began to reintensify and was upgraded to tropical storm intensity before exiting the coast of North Carolina around 1900 UTC 24 July. This presentation analyzes the factors which contributed to Danny's reintensification. Primarily, Danny interacted with an upstream trough and associated jet while exiting the Appalachian Mountains. The resultant vortex tube stretching in a nearly moist-neutral environment allowed for the redevelopment of Danny while still over land.