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 word bikini comes from Bikini atoll, the name of one of the Marshall Islands in the western Pacific, where atomic-bomb tests were performed in 1946. One theory of the coinage is that the effect achieved by a scantily clad woman appearing in public may be compared to the effect of an A-bomb blast.