Swirl ratio

[Caleb Routt]

So what exatly is swirl ratio? And what does it have to do with creating suction vorticies? I have thought about it and ive came to the conclution that all it means is how much horizontal circulation is vs the updraft of the thunderstorm

 

[Jeff Duda]

Swirl ratio is the ratio of the tangential flow in a tornado to the radial flow. High swirl ratios tend to be associated with multicell tornado structure where you get suction vortices, whereas low swirl ratios tend to be associated with single cell tornadoes consisting mostly of inflow, a corner flow region, and then updraft aloft.

 

[Caleb Routt]

So what your saying is that high swirl ratio means that the tornado's updraft is equal to the horizontal winds? Im guessing that if you had a tornado that was really updraft dominated that it would be harder to produce vorticies? Why is this? Why does it matter how high the swirl ratio is to produce vortices?

 

[Jeff Duda]

No, the tangential flow is the circular flow in a horizontal plane around the center of the tornado, whereas the radial flow is horizontal flow directly towards the center of the tornado. I don't think swirl ratio incorporates vertical motion. However, I believe low swirl ratio tornadoes do have that single-cell structure that is dominated by updraft. I have no idea why it works the way it does.