A simplified, conceptual demonstration of one possible way that tornadoes form. This is the process known as bottom-up tornadogenesis. A visual example is provided for both non-supercell and supercell tornadoes. For reference and ease of access, this is a short clip from my "Front Line Storm Spotting" presentation. Watch the full presentation here:    • Front Line Storm Spotting  
Much of the photos and video courtesy Andrew Pritchard and used with permission.