The 12 July 1995 Pinellas County, Florida, tornado/waterspout

On 17 July 1995, a tornado developed over south St. Petersburg, Florida, pr oducing F1 damage and injuring one person before moving offshore. The torna do/waterspout was within 25 km of the Ruskin Florida WSR-88D, which provide d detailed radar data. The preconvective environment was characterized by l arge CAFE and weak to moderate vertical wind shear, due in part to a weak u pper-level cold core trough. The tornado parent cell developed rapidly in r esponse to surface mesoscale boundary interactions. This cell was relativel y short lived and nonsteady and, thus, classified as multicellular. Availab le data suggest that tornadogenesis occurred due to vertical stretching of preexisting vertical vorticity associated with one of the foregoing boundar ies. Evidence suggests that the stretching was due to both storm updraft an d convergence associated with storm downdraft. The parent cell contained a midlevel mesocyclone and mesoanticyclone pair, consistent with the proximit y hodograph. This vortex pair and the tornadic circulation were separate an d it is unclear what role the vortex pair contributed to tornadogenesis. Th is case is important since it demonstrates that a nonsupercell tornado can be anticipated before a single-Doppler radar tornado vertex signature (TVS) appears. using current nonsupercell tornadogenesis theories. Such anticipa tion is essential to operational forecasters in the Notional Weather Servic e, especially for cases when tornadoes are either undetectable by radar or when a radar-detected TVS does not provide sufficient lead time.