Non-supercellular tornadoes are often called waterspouts or landspouts, depending on nature the surface over which they occur. Spouts are thought to form mainly a result of the stretching of pre-existing vertical vorticity along boundaries, rather than the tilting of vorticity and subsequent stretching that is important in supercell tornadoes. Spout-type tornadoes are most common when winds are weak in the lower troposphere and high values of CAPE are released in the lowest 3 kilometres. This type of tornado usually causes only F0 or F1 damage, but F2 damage has been reported in the U.S. and in Europe, too.

Fig. 2.6. The formation of a non-mesocyclonic tornado along a convergence line. From Wakimoto and Wilson (1989).

Spout-type tornadoes are most common when winds are weak in the lower troposphere. This type of tornado usually causes only F0 or F1 damage, but F2 damage has been reported in the U.S. and in Europe, too.