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 Real Origin of the Bikini Wasn't a Nuclear Explosion. 55 years ago today, the United States tested a hydrogen bomb over Namu island, in the Bikini Atoll, Pacific Ocean. The 15 megaton bomb exploded at 15,000 feet, causing a four-mile fireball, 500 times brighter than the Sun.