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.
Kepler data has surfaced other near Earth-size planets in the habitable zone in the past. In fact, Thursday's announcement of Kepler-452b was also accompanied by news of 12 other new planet candidates near Earth size, and in orbit in their star's habitable zone. Of those, nine orbit stars are similar to our sun.