Do you mean this?
If so, it's actually quite easy.
1) Start with a skinny barrel in the "tornado" colour
2) Put rings of clear around the barrel - make sure they don't touch - alternatively trail a spiral of clear around the barrel like a screw thread or helter skelter.
3) Gently melt the clear into the barrel. Don't marver,
4) Encase the whole bead.
5) I squashed this bead to exaggerate the spiral effect but you can leave it round.
Thanks for posting this Sal, I was directed to your instructions by Karen 'Essex Girl'
All very helpful.
Thanks folks.
Regards . . . Andy