Tornado Development

[Matt Gingery]

We studied tornadoes last semester in detail. We talked about meso type, and existing eddies at the surface that get drawn up into regular thunderstorm updrafts and in most cases become land spouts. Why are most of these dynes compensation type tornadoes, land spouts etc. weaker? Can there be EF-3 and higher tornadoes from these stretched vertical columns?

 

[Shane Adams]

We studied tornadoes last semester in detail. We talked about meso type, and existing eddies at the surface that get drawn up into regular thunderstorm updrafts and in most cases become land spouts. Why are most of these dynes compensation type tornadoes, land spouts etc. weaker? Can there be EF-3 and higher tornadoes from these stretched vertical columns?

My guess is because landspout type tornadoes draw the body of their rotation from pre-existing eddies near the ground, and merely use the parent storm's updraft to stretch this rotation vertically. On the other hand, a typical mesocyclonic tornado relies on the parent storm's updraft for its rotation source, meaning it's influenced by upper air dynamics (the strongest winds we know of), allowing the potential for extreme wind speeds in the rotation after it's stretched vertically.

A crude answer scientifically, but hopefully you understand what I'm saying. Perhaps someone more schooled can elaborate.

Aside: I do believe there have been documented cases of F3 caliber damage from landspout type tornadoes, but I could be mistaken.

 

[Matt Gingery]

Thanks for the reply. That makes total sense to me. I was told in the class that most of the weaker tornadoes occur in air mass type tstorms and are derived from this stretching. I find it interesting that its possible for these type to produce EF-3 type damage. Some of the more eligant tornadoes are land spouts. They always pick up so much dust that they look meaner than they actually are. From what we studied they are common along the down slopes of the Colorado Rockies when high pressure draws winds from the east and southeast converging with the downslope air. Seems to me that they could be stronger in that type of scenario. I appreciate it!!

 

[Dann Cianca]

Aside: I do believe there have been documented cases of F3 caliber damage from landspout type tornadoes, but I could be mistaken.

One of the 1988 Denver landspouts was rated F3. It destroyed a furniture store on the corner of Evans and Broadway.



It should be said also that there isn't only one way that mesocyclonic tornadoes form. There seem to be various ways they form, from tighter circulations within the meso, from vorticity pulled into the updraft (similar to landspout formation), boundary interaction (moisture discontinuities, outflow boundaries, RFD, etc).

 

[Matt Gingery]

Thanks Dan! It seems like the front range near Denver is notorious for the landspout type tornadoes.

 

[Dann Cianca]

Thanks Dan! It seems like the front range near Denver is notorious for the landspout type tornadoes.

Hi Matt, thanks to the Denver Cyclone and Denver Convergence and Vorticity Zone (both can happen simultaneously or separately), the area is a hotbed for non-supercell tornadoes.

 

[Paul Knightley]

It's sometimes a good idea to take a step back and think that tornadoes probably form in a similar way, fundamentally - that is that near-ground vertical vorticity is stretched by an upraught, and the conservtion of angular momentum causes it to speed up.
Of course, you then have to work out where this vorticity has come from, as this is where the differing environments come in. Storms with weak shear but close to a boundary can pick up this vorticity from the ambient environment, where misocyclones form along the boundary and are then picked up by passing updraughts. Within a supercell storm, it is speculated that the RFD may increase the low-level vertical vorticity to a level where it can be stretched by the updraught (mesocyclone) into a tornado.