14C.5 Internal structure of Hurricane Isabel at landfall

Thursday, 1 May 2008: 11:15 AM
Palms H (Wyndham Orlando Resort)
Renee Curry, Univ. of Oklahoma, Norman, OK; and M. I. Biggerstaff

Forecast models have a need for observational data on meso- and convective scales to validate numerical forecasts and improve model parameterizations, especially during landfalling hurricanes. Ground-based instruments, such as mobile radars, have high temporal and spatial observations that provide the necessary data to test model performance.

In September 2003, two mobile C-band Doppler radars, the Shared Mobile Teaching and Research Radars (SMART-R's) collected data as Hurricane Isabel made landfall along the North Carolina coast. The SMART-R's collected twelve and a half hours of dual-Doppler data, providing high-resolution volumetric scans every three minutes. Analyses of this data provide insight into the small-scale variability of precipitation and winds associated with the advection and evolution of mesoscale rainbands and an asymmetric vortex. Within the rainbands, there was a radially-oriented connecting band along the coast with a mesoscale updraft at low levels, in contrast to the mesoscale downdraft found in conceptual models of hurricane rainbands. Analyses of the eyewall show the structure of the asymmetric vortex and a lack of strong vertical drafts. The weak downdrafts in the eyewall and the rainbands did not efficiently transport high momentum air to the surface, thereby limiting the potential wind damage as the storm made landfall.

This dataset is unique in the respect that there has been no published study of a mobile, dual-Doppler analysis of a landfalling hurricane and this study illustrates the utility of mobile Doppler radars to examine hurricane structure and evolution at landfall.

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