NOVEL RADAR Observations of Turbulent Eddies in the Lower Levels of Intense Hurricane RITA (2005)

The small-scale asymmetric structure of an eyewall replacement cycle in Hurricane Rita (2005) near peak intensity is presented from novel airborne Doppler radar observations using the Imaging Wind and Rain Airborne Profiler (IWRAP). The measurements and three-dimensional wind vector calculations reveal the ubiquitous presence of turbulent eddies in the storm core at an unprecedented grid spacing of 250 m in the horizontal and 30 m in the vertical. A large eddy numerical simulation of a quasi-idealized hurricane at a grid spacing of 60 m was performed to understand the resolution and sampling characteristics of the IWRAP instrument.

The turbulent eddies in the IWRAP data contain horizontal wind speeds up to ~ 90 m/s and have a consistent periodicity present in horizontal and vertical winds as well as the Ku/C band reflectivity fields. These observations suggest a possible connection to vortex Rossby waves, which are known to play a role in concentric eyewall evolution. Supporting data from the NOAA WP-3D tail Doppler and lower fuselage radars, coincident with IWRAP, help to reveal the evolution of the vortex-scale dynamics during the eyewall replacement process.