Low Swirl Fluid

[Caleb Routt]

Can anyone exsplain what "low swirl flow" is? Im having a hard time grasping what he is talking about when a tornado passes over a diffrent surface roughness. He says that when you increase surface roughness the tornado looses angular momentum therefore pulling in low swirl fluid through cyclostrophic balance and changong the corner flow. This is some pretty complicated stuff: https://ams.confex.com/ams/27SLS/videogateway.cgi/id/28354?recordingid=28354

The part where he discusses this starts at 2:12 of this clip.

 

[Austin Jones]

I'm no expert, but I watched the video ( I thought it was very interesting, thank you) and the context in which he uses the term "low swirl fluid" leads me to believe that it is simply air slowed by the "blocks" or "rough surfaces". At 3:27 he shows the pool/stream of slower moving air that sits in the wake of a block and he calls it "low swirl fluid". I would imagine this air would have less kinetic energy as it enters the tornado, therefore effecting the tornado flow, strength, and angular momentum.

 

[Jeff Duda]

See http://tornado.sfsu.edu/geosciences...xamples/BasicTornadoStructure/SwirlRatio.html for a definition.

Typically, tornadoes with low swirl ratio have strong inflow and are of the one-cell type. Low swirl ratio tornadoes also tend to have a narrower diameter, if I'm not mistaken.
Typically, tornadoes with high swirl ratio are either two-cell or multi-cell type. High swirl ratio tornadoes tend to have a larger circulation.