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Charles H. Paxton and Daniel A. Sobien

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.

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Richard J. Davis and Charles H. Paxton
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Waylon G. Collins, Charles H. Paxton, and Joseph H. Golden
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Waylon G. Collins, Charles H. Paxton, and Joseph H. Golden

Abstract

On 12 July 1995, a tornado developed over south St. Petersburg, Florida, producing F1 damage and injuring one person before moving offshore. The tornado/waterspout was within 25 km of the Ruskin Florida WSR-88D, which provided detailed radar data. The preconvective environment was characterized by large CAPE and weak to moderate vertical wind shear, due in part to a weak upper-level cold core trough. The tornado parent cell developed rapidly in response to surface mesoscale boundary interactions. This cell was relatively short lived and nonsteady and, thus, classified as multicellular. Available data suggest that tornadogenesis occurred due to vertical stretching of preexisting vertical vorticity associated with one of the foregoing boundaries. Evidence suggests that the stretching was due to both storm updraft and convergence associated with storm downdraft. The parent cell contained a midlevel mesocyclone and mesoanticyclone pair, consistent with the proximity hodograph. This vortex pair and the tornadic circulation were separate and it is unclear what role the vortex pair contributed to tornadogenesis. This case is important since it demonstrates that a nonsupercell tornado can be anticipated before a single-Doppler radar tornado vortex signature (TVS) appears, using current nonsupercell tornadogenesis theories. Such anticipation is essential to operational forecasters in the National Weather Service, especially for cases when tornadoes are either undetectable by radar or when a radar-detected TVS does not provide sufficient lead time.

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