Developing a waterspout forecast protocol for the Florida Keys wet season

Waterspouts pose a hazard to commercial and recreational marine interests, and on rare occasions can cause damage inland if they move onshore. The frequency of non-supercell waterspouts in the vicinity of the Florida Keys is higher than any other location in the United States, and is arguably the highest in the world. There is strong evidence that waterspouts are under reported in the Keys, possibly by an order of magnitude. The National Climatic Data Center's Storm Data and Unusual Weather Phenomenon database for the locally defined wet season of June through September 2007-2012 was used in this investigation. Parameters were derived from the Key West 1200 UTC soundings with 132 of 722 associated with at least one waterspout report. Because of the tropical marine environment over the Florida Keys in the summer, the soundings were considered proximal, both spatially and temporally, with waterspouts reported near the island chain. The parameters obtained from these soundings included thermodynamic and kinematic profiles, and derived stability and convective indices. The parameters from the days when waterspouts were reported were compared to those from the days on which no waterspouts were reported, with the goal of identifying which parameters were indicative of a day more conducive to waterspout development. It was not possible to investigate the more general concept of comparing days when waterspouts did not occur (versus not reported), because waterspouts often go unreported and are not detectable via other means (i.e., radar or satellite). Each parameter comparison was examined for statistical significance and consistency. Sounding parameters that showed not only statistical significance, but also utility in the forecast process, were given consideration in the development of a waterspout forecast protocol.