| One of the most complete datasets of a single tropical cyclone was recorded in Hurricane Elena (1985), as the storm made a three-day, anticyclonic loop in the Gulf of Mexico. Eighty-eight radial flight legs and 1,142 radar scans were collected as the storm intensified from a disorganized category two to an intense category three hurricane. This unprecedented amount of data was used to analyze the evolution of both the symmetric structure and azimuthal asymmetries within the storm.; On the first day of study, Elena was under the influence of strong vertical wind shear from an upper tropospheric trough to the west. The storm was disorganized, with no discernable eyewall and nearly steady values of tangential wind and relative vorticity. Early on the second day, a near superposition and constructive interference occurred between the trough and Elena, initiating height falls and tangential wind spin-up in the core, and coincident with upward vertical velocities and the radial gradient of reflectivity becoming concentrated around the 30 km radius. During this period of intensification, Elena's rainfall pattern exhibited a strong wavenumber one asymmetry with the highest reflectivity in the eyewall to the north of the center, or to the left of the vertical wind shear.; Once convection and a diabatic heating maximum were established in the eyewall, a sharp localized vorticity maximum emerged, with much lower values on either side. This barotropically unstable vorticity profile was noted to breakdown near the time of peak intensity, accompanied by the appearance of an elliptical eyewall, asymmetric mixing between the eye and eyewall, and propagating inner spiral rainbands with properties consistent with vortex Rossby wave theory.; The asymmetric mixing between the eye and eyewall appeared to act as a brake on intensification from which Elena was unable to recover due the storm's proximity to land and the ingestion of low equivalent potential temperature air. Subsequently, Elena's spindown was marked by an increase in the outward slope of the eyewall in the upper troposphere and weakened convection aloft due a strongly tilted, shallow secondary circulation with an 850-hPa outflow jet that further enhanced spindown of the vortex. |
