Dr. Rogers presented a seminar on “Multi-scale Structure and Evolution of Earl (2010) during Rapid Intensification”.
The structure and evolution of the inner core of Hurricane Earl (2010) during its rapid intensification is studied here, using airborne Doppler and Global Positioning System dropsonde data. The results shown here depict the rapid intensification of Earl as occurring in two stages. During the early stage, which covered ~24 h, Earl was a tropical storm experiencing moderate northeasterly shear with an asymmetric distribution of convection, and the symmetric structure was shallow, broad, and diffuse. The upper-level circulation center was significantly displaced from the lower-level circulation at the beginning of this stage. Deep, vigorous convection, termed convective bursts here, was located on the east side of the storm that appeared to play a role in positioning the upper-level cyclonic circulation center above the low-level center. By the end of this stage the vortex was aligned and extended over a deep layer, and rapid intensification began. During the late stage rapid intensification continued, as Earl intensified ~20 m s-1 in the 24-h period comprising this stage. The vortex remained aligned in the presence of weaker vertical shear, though azimuthal asymmetries in the flow field persisted that were characteristic of vortices in shear. Convective bursts were noted near the radius of maximum winds during this stage, with the majority of bursts located just inside the radius of maximum winds.
Each of the two stages described here raises questions about the role of convective- and vortex-scale processes in rapid intensification. During the early stage the focus is on the role of convective bursts, and their associated mesoscale convective system, on vortex alignment and the onset of rapid intensification. During the late stage the focus is on the processes that explain the observed radial distribution of convective bursts which peak inside the radius of maximum winds.
A copy of the presentation is available on the anonymous ftp site: