LONG-TERM GOAL The wave conditions in severe large storm waves are often critical to the survival design of marine structures. This project is directed toward the careful analysis of airplane-based scanning radar altimeter (SRA) data from NASA flights into hurricanes to extract the detailed geometry of large storm waves. OBJECTIVES Walsh has recorded SRA data in flights over the Hurricane Bonnie (1998) and Hurricane Floyd (1999) storm systems. The present project is directed toward developing

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... w analysis and software for effectively analyzing such data, and then using the new methodology to extract the structure and related statistics of the individual large waves. Answers are sought to such significant questions as: How nonlinear are large storm waves, what are typical and extreme crest and trough lengths, and are the very large waves isolated or do they come in groups one after another APPROACH An airplane flying through maelstrom of hurricane winds is hardly an ideal platform from which to take measurements. As would be expected, SRA data contains substantial noise and error spikes attributable to violent airplane motion. Special analysis techniques have to be carefully designed to extract the correct scientific relationships from out of such messy data. The large waves in confused seas are difficult to describe. Just what is a wave height or wave length in the chaotic storm condition? After considerable effort, the following "quartile-wave" definitions are proposed. All of the water surface elevations above and below mean water level from the grid of the SRA measurements over a specified region are ranked in order of increasing size. The 50 percentile elevation corresponds very nearly to the mean water level. A wave crest is defined as a "bump" of