WATERSPOUTS AND TORNADOES OVER SOUTH FLORIDA

JOSEPH H. GOLDEN National Hurricane Center, NOOA, Miami, Fla.

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Abstract

An analysis of the Lower Matecumbe Key 1967 waterspout data is presented. It was found that the flow field synthesized across the spray vortex of the second, larger waterspout is closely approximated by a Rankine-combined vortex with solid rotation over a circle 24 m in diameter. Five major tornadoes were documented in the Greater Miami area during 1968, and this anomalous number is ascribed to the development of strong localized zones of convergence on the mesoscale along or slightly inland from the southeast coast where the prevailing southwesterly tropospheric flow interacts with the sea breeze induced by the Florida Peninsula. On the other hand, the large number of waterspouts documented in the Lower Keys during the summer of 1968 were spawned by cumulus congestus cloud lines embedded in a very warm undisturbed trade-wind flow.

Extensive documentation of close-range observations was obtained for an unusually large “tornadic waterspout” that passed through a crowded coastal marina in Miami. Evidence concerning the formation process, flow kinematics, and the problem of a “flying houseboat” are presented.

Abstract

An analysis of the Lower Matecumbe Key 1967 waterspout data is presented. It was found that the flow field synthesized across the spray vortex of the second, larger waterspout is closely approximated by a Rankine-combined vortex with solid rotation over a circle 24 m in diameter. Five major tornadoes were documented in the Greater Miami area during 1968, and this anomalous number is ascribed to the development of strong localized zones of convergence on the mesoscale along or slightly inland from the southeast coast where the prevailing southwesterly tropospheric flow interacts with the sea breeze induced by the Florida Peninsula. On the other hand, the large number of waterspouts documented in the Lower Keys during the summer of 1968 were spawned by cumulus congestus cloud lines embedded in a very warm undisturbed trade-wind flow.

Extensive documentation of close-range observations was obtained for an unusually large “tornadic waterspout” that passed through a crowded coastal marina in Miami. Evidence concerning the formation process, flow kinematics, and the problem of a “flying houseboat” are presented.

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