temperature and the vortex would now be barotropic [@davies15].

Geometric self-similarity is occasionally seen in high-resolution numerical simulations of tornadic supercells [@lewellenssykes97; @adlerman00; @eyink13] and also in Doppler radar and reflectivity observations [@bluestein00b; @nova04]. As an example, in the reflectivity image in Figure \[fig:tornado\_fractal\] we can see self-similarity on two different scales demonstrating itself as “hooks on a hook.” This is likely due to the existence of subvortices within the larger vortex. High-quality video recordings of some recent tornadoes depict mini suction vortices (subvortices of suction vortices), confirming the smallest scale of the hierarchy in Figure \[fig:hier-vort\] [@wadena10; @elrenovideo13].

![Hierarchy of known vortex scales in tornadic supercells; © AMS, [@church77].[]{data-label="fig:hier-vort"}](hier-vort.png){height="0.4\textheight"}

![Examples of ground marks left behind by suction vortices embedded inside tornadoes. Locations and dates of occurrences are: (A.1) Decatur, Illinois tornado 3 April 1974; (A.2) Magnet, Nebraska tornado, 6 May 1975; (A.3) Homer Lake, Indiana tornado, 3 April 1974; (A.4) Dubuque, Iowa tornado, 28 September 1972; (A.5) and (A.6) Pearsall, Texas tornado, 15 April 1973; (A.7) Mattoon Lake, Illinois tornado, 21 August 1977; (A.8) Grand Island, Nebraska tornado, 3 June 1980. © AMS, [@fujita81].[]{data-label="fig:suctionspots"}](suctionspotsFujita82_v3){width="89.00000%"}

![A reflectivity image of a tornado showing self-similarity and a possible fractal structure; © Joshua 