Extended Abstract (1.4M)3.3
Fine scale analysis of the convective scale wind fields of Katrina and their relationship to the surge event
Richard G. Henning, Consulting Meteorologist, Niceville, FL
Over the last two years, this author has written over 200 reports detailing the impact of Hurricanes Ivan (2004) and Katrina (2005) at specific property addresses primarily on behalf of individual property owners involved in litigation with their insurance carriers. As a private consulting meteorologist, the task of reconstructing a chronology of events with regard to the arrival of wind and surge at specific locations is a far different undertaking than a government agency, such as NHC in their storm reports, attempting to characterize the scope of a storm as a whole, for dissemination to the public through the media.
The importance of convective scale features cannot be overstated with regard to their ability to translate extreme boundary layer winds, routinely measured using aircraft reconnaissance dropsondes, down to the surface at specific locations for brief periods in the form of three second gusts. It will be shown that many locations along the immediate shoreline in both Ivan and Katrina saw extreme winds either in advance of, or in conjunction with, the period of highest surge inundation. While the surge literally washed away much of the on-site forensic evidence of these extreme wind events, use of WSR-88D radar and aircraft reconnaissance data can establish very high confidence wind estimates for particular neighborhoods where no in-situ observations were made.
This presentation will discuss several cases where an examination of reflectivity and radial velocity products reveals discrete mesocyclones and collapsing supercells which, when superimposed upon the ambient larger scale tangential winds of the parent hurricane vortex, support localized wind velocities which could have easily produced significant wind damage. It is a practical application of the research done in recent years by Blackwell et al at the University of South Alabama Coastal Weather Research Center.
This paper also examines alternatives to broad brush, oversimplified, attempts at characterizing the destructive potential of storms such as Ivan and Katrina. It demonstrates that use of the Saffir Simpson Scale, while convenient for the media and easily understood by the public, is often highly misleading in the investigation of the relative contribution of storm damage to a specific property caused by wind and/or water (as well as the temporal relationship between the two forces, often an essential aspect to resolving disputes between insurance carriers and their customers). Alternatives, such as the Integrated Kinetic Energy scheme proposed by Powell and Reinhold in the April 2007 Bulletin of the AMS, to characterize the storm on a large scale, as well as techniques to integrate depictions of mesoscale and convective scale features for analysis on the scale of specific neighborhoods, will be examined.
Session 3, The Role of the CCM in Severe Weather
Wednesday, 23 January 2008, 11:00 AM-12:00 PM, R04
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