Observational estimates of turbulence characteristics in the low-level troposphere of intense hurricanes

This talk presents estimates of the characteristics of turbulent flow in the low-level troposphere of an intense eyewall using in-situ aircraft observations. The flight-level data collected by research aircraft that penetrated the low-level (~500 m) eyewalls of Category 5 Hurricane Hugo (1989), Category 4 Hurricane Allen (1980) and Category 5 Hurricane David (1986) are analyzed. Estimates of turbulent vertical and horizontal momentum flux, vertical and horizontal eddy diffusivity and corresponding mixing lengths, as well as turbulent kinetic energy, are obtained before and during the eyewall penetrations. The results offer new quantitative estimates of sub-grid scale turbulence characteristics for theoretical research on tropical cyclone intensification and maximum intensity and should offer useful guidance also in numerical weather prediction efforts aimed at improving the forecast of hurricane intensity.