Tornado frequency worldwide

Tornadoes have been reported widely (Table 1), especially in the central Great Plains of the USA (Fig 1), where they also can be most violent.

Table 1. Tornado frequency and intensity in select geographical regions (1,2,3,4).

Fig 1. Tornado frequency in the USA. The frequency increases from grey to red (Source: the Weather Channel).

The great majority of tornadoes in New Zealand occur in the North Island, particularly around the Bay of Plenty at about 38° S, and along to Auckland, where there were about 17 in a small region (5). There is another concentration on the western coast of Taranaki near New Plymouth, and twelve were observed at that town between 1961-1975. The places with most tornadoes tend to be relatively well populated, so there may be many more unobserved tornadoes elsewhere.

1. Fujita, T.T. 1973. Tornadoes around the world. Weatherwise, 26, 56-83.
2. Grazulis, T.P. 1991. Significant tornadoes, 1880-1989. Tornado Project, PO Box 302, St. Johnsbury, VT 05819 USA, 512pp.
3. Goliger, A.M., R.V. Milford, B.F. Adam, and M. Edwards, 1997. Inkanyamba: tornadoes in South Africa. United Litho Publisher, 77pp.
4. Geerts, B. and M. Noke-Raico 1995. Tornadoes in Australia: Do we really know ? Bull. Austr. Meteor. and Ocean. Soc., 8, 46-51. 
5. Sturman, A.P. and N. Tapper 1996. The Weather and Climate of Australia and New Zealand (Oxford) 476pp. (on p292 they publish a diagram initially constructed by Tomlinson and Nicol in 1976, showing the location of tornadoes observed during 1961-1975 in New Zealand)