Hurricane Danny exhibited various characteristics and structural evolutions during its life span. This work examines the structural changes of the storm upon entering Mobile Bay, and the three-
dimensional structure of its long-lived remnants as it passed over Birmingham, Alabama. Animation of radar reflectivity showed that prior to entering Mobile Bay, the spiral precipitation pattern associated with Danny was fairly symmetric. After entering the bay,
radar echoes over the eastern semi-circle of the circulation of Danny began to collapse. The remaining western rainband became stationary; resulting in copious rainfall across much of the west shore of Mobile Bay.
Through surface isobaric and virtual temperature analyses, it is found that hurricane Danny was accompanied by a coastal temperature and moisture gradient. This gradient was enhanced as Danny approached the coast. The thermal gradient, with the oceanic air having higher virtual temperature, is thought to have induced a land breeze circulation in the boundary layer. The presence of the land breeze circulation is supported by a west-east asymmetric distribution of wind speed around Danny--winds on the west side of Danny were stronger than on the east side. Concurrent with the collapse of the precipitation echoes on the east side of Danny was the emergence of a cool pool of air on the west side. It is proposed that baroclinic processes were involved in focusing the precipitation on the west side of Danny resulting in devastating rainfall totals.
After moving inland and weakening, Danny did not dissipate completely. The remnant circulation passed over Birmingham, AL (BMX). Cross-sectional analyses revealed that Danny (a) consisted of a cold
core cyclone in the boundary layer centered over BMX; (b) a warm-core cyclone in the lower troposphere; (c) a warm-core open wave in the mid-troposphere;(d) a cold-core anticyclone in the upper troposphere, tropopause, and lower stratosphere. In addition, a convectively unstable boundary layer was present outside the immediate environment of Danny. The available warm and moist air from the boundary layer is recognized to be an important energy source for the maintenance of the circulation and the warm core tropospheric structure of Danny over land