Resonant Interaction between an Atmospheric Gravity Wave and Shallow Water Wave along Florida's West Coast

Abstract

On 25 March 1995, a large solitary wave, seemingly from nowhere, washed ashore along the normally tranquil Gulf Coast of Florida from Tampa Bay to south of Naples. On this Saturday morning, many beachgoers and coastal residents saw either a large wave, a surge, or a seiche. The wave was typically described as 3 m or greater, breaking between 0.5 and 3 km offshore, and taking 120–180 s to arrive at the shore. Just prior to the wave's arrival at the beach, witnesses reported a rapid runout of water, then a huge 15–25-m runup of water onto the beach corresponding to a 2–3-m vertical run-up height. Some people reported several smaller waves. This was likely due to local effects. This wave was generated and amplified by a large-amplitude atmospheric gravity wave transiting southeastward over the eastern Gulf of Mexico. The atmospheric gravity wave and the water wave moved over a channel of water depth sufficient to maintain the waves in phase allowing resonation of the shallow water wave. Surface winds appeared to have a negligible affect, increasing only slightly (3–5 m s−1) along the path of the atmospheric gravity wave and opposing propagation of the water wave.