Literally, in order for a vortex to be classified as a tornado, it must be in contact with the ground and the cloud base. Weather scientists haven't found it so simple in practice, however, to classify and define tornadoes (per this essay by Doswell).
Bikini Island, 2015. Credit: Emlyn Hughes. (Phys.org)âA team of researchers from Columbia University in New York has found that all of the Marshall Islands involved in nuclear tests by the U.S. are now habitable, except for Bikini Atoll.
The thing is, at Bikini Atoll you're diving in the greatest warship wreck museum in the world. We were there to see the historic warships and the results of an atomic attack on a naval fleet. Unlike dive destinations like the Galapagos Islands and Great Barrier Reef, we were not there to look at the fish!