Terrain/Corner Flow

[Caleb Routt]

Ok so I do realize that mountains can change the corner flow in the tornado thereby increasing its intensity and size. So just a thought is it possible that the reason why tornadoes seem to intensify on downhill slopes is because inflow is greater on the backside because its easier for air to move downhill than up?

 

[rdale]

There's no real evidence that tornadoES intensify on the downslope, and I'm not sure what you mean about air is easier to "move" downhill? There are some studies that suggest downslope intensification and some which say the valley reduces a storm's threat. Either way - it's not a given

https://www.google.com/url?sa=t&rct...RZoT8oO4sNUCVpn8A&sig2=9S_5ISDOLP4qP0L1m8Ys8Q

 

[Dan Robinson]

I've wondered if the uphill side is simply acting as a partial barrier to near-surface inflow, which is removed on the downhill side.

 

[Patrick Marsh]

The theoretical underpinnings of the "downhill moving, intensifying tornado" is that the vorticity stretches in the vertical, causing the diameter to contract, thereby increasing the angular velocity in order to conserve angular momentum. It's the spinning ice-skater phenomenon.

Personally I'm not sold that a change in a few hundred feet has that much of an impact on a voracity column that can stretch into the vertical for several kilometers.

Personally, I would tend to lean toward an argument suggesting the valley acts as a channel, increasing low-level velocity given a favorable storm motion. And even that would be difficult to ascertain given how much we still down know about tornado formation, maintenance, and decay.

 

[Shawn Schuman]

Lyza & Knupp from UA Huntsville had an interesting presentation on terrain influences at the most recent SLS conference. It doesn't really dig into the processes that may be happening, but it does investigate the effect of terrain on several tornadoes in the Southeast. There's a recording of the presentation here.

https://ams.confex.com/ams/27SLS/webprogram/Paper255844.html

Some very interesting behaviors, including tornadoes whose paths deviate to roughly follow the contours of a terrain feature.