by tornadochaser » Tue Apr 12, 2011 2:03 pm
Those are cumulus mammatus clouds. Usually the underside of an anvil shaped thunderstorm cell. Not related to any tornadic development. Usually these are seen on the lead edge of an approaching thunderstorm before the gust front passes. They can have a boiling, swirling appearance that to the untrained eye could be mistaken for small wall clouds or funnels.
Tornados form from mesocyclonic supercells. the whole cell is actually rotating, and sometimes that rotation combined with windshear causes wall clouds and/or tornados.
Fowl University