<P> Supercells can occur anywhere in the world under the right weather conditions . The first storm to be identified as the supercell type was the Wokingham storm over England, which was studied by Keith Browning and Frank Ludlam in 1962 . Browning did the initial work that was followed up by Lemon and Doswell to develop the modern conceptual model of the supercell . To the extent that records are available, supercells are most frequent in the Great Plains of the central United States and southern Canada extending into the southeastern U.S. and northern Mexico; east - central Argentina and adjacent regions of Uruguay; Bangladesh and parts of eastern India; South Africa; and eastern Australia . Supercells occur occasionally in many other mid-latitude regions, including Eastern China and throughout Europe . The areas with highest frequencies of supercells are similar to those with the most occurrences of tornadoes; see tornado climatology and Tornado Alley . </P> <P> The current conceptual model of a supercell was described in Severe Thunderstorm Evolution and Mesocyclone Structure as Related to Tornadogenesis by Leslie R. Lemon and Charles A. Doswell III . (See Lemon technique). </P> <P> Supercells derive their rotation through tilting of horizontal vorticity (an invisible horizontal vortex) caused by wind shear . Strong updrafts lift the air turning about a horizontal axis and cause this air to turn about a vertical axis . This forms the deep rotating updraft, the mesocyclone . </P> <P> A cap or capping inversion is usually required to form an updraft of sufficient strength . The cap puts an inverted (warm - above - cold) layer above a normal (cold - above - warm) boundary layer, and by preventing warm surface air from rising, allows one or both of the following: </P>

Where does the rotation of the supercell come from
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