Large Wave at Daytona Beach, Florida, Explained as a Squall-line Surge

  • Asburry H Sallenger, Jr.
  • Jeffrey H List
  • Guy Gelfenbaum
  • Richard P Stumpf
Keywords: Freak waves, overwash, forced wave, wave runup.

Abstract

On a clear calm evening during July 1992, an anomalously large wave, reportedly 6 m high, struck the Daytona Beach, Florida area. We hypothesize that a squall line and associated pressure jump, traveling at the speed of a free gravity wave, coupled resonantly with the sea surface forming the large wave or "squall-line surge." The wave was forced along the length of the squall line, with the greatest amplitude occurring at the water depth satisfying the resonant condition. Radar observations showed a strong squall line moving at a steady speed for several hundred kilometers parallel, to the coast from Georgia towards central Florida. The squall line dissipated 10 km north of Daytona Beach; any forced wave would then propagate freely and refract. Wave refraction analyses predict a longshore distribution of wave heights consistent with field measurements of maximum wave runup.
Published
1995-10-17
Section
Technical Communications