Gravity Waves Make Tornadoes

[rdale]

There is clearly better chances for a tornado when you have a strongly rotating meso, but there's no criteria where you can say "rotation > x = tornado."

We saw that this weekend when Atlanta issued a Tornado Emergency because they saw strong rotation on radar, but not even strong winds were reported on the ground.

 

[Willie Dines]

I understand what you mean and it's true in what you say, purely because the weather is constantly changing, which is what makes the weather as intrigueing as it is

Willie

 

[Jeff Miller]

Gravity Waves

Short YouTube video of gravity waves in action:

http://www.youtube.com/watch?v=yXnkzeCU3bE

This may make it a little more visually clearer - in a way. Though for me it just raises more questions than anything.

 

[D. Hayes]

yea that's the video I was talking about. The term "Gravity Wave" is really used to loosely so I'd have to retract my gravity wave statement given to this video above.. I would consider a gravity wave to be a invisible gravitational force creating a disturbance in the atmosphere across a flat area. Not a mountain/hill creating a wave in air flow like this:

Now if you replaced the mountain with "a change in gravity" you would have a Gravity Wave.

After looking at the Google maps terrain mode (Tama, Iowa) where the video was shot. I'd think that video was a "mountain wave cloud".

Far as creating tornadoes I don't see how a real gravity wave would make a difference. I mean wouldn't both air masses be equally affected by differences in gravitational pull? If anything I would think it would disrupt the tornado cycle. Of course I could be 100% wrong. Don't shoot me, I'm still learning here.

 

[Eddie Natenberg]

Thought this would be a good link for all the details on this research:

http://www.atmos.uah.edu/mips/personnel/tim/

Eddie

 

[rdale]

Good fine Eddie! That helps explain much more what his theory is about...

 

[Darrin Rasberry]

Here is an offering from the SPC regarding the Jarrell, Texas tornado. Since I'm not as versed on the terms as a published scientist, I'll leave the explanation to him:

Coincidental with the onset of deep convection near Waco was the passage of the MCS-generated gravity wave. Having originated in Arkansas, the central Texas portion of this feature moved southwestward in-step with the surface wave until around 2100 UTC, at which time the cold front overtook the dry line near Austin. The advance of the gravity wave and its motion relative to the developing storms is readily apparent in the animated satellite imagery shown in Figure 6.

As previously noted, while the lower tropospheric environment over central Texas on the afternoon of 27 May 1997 was very unstable, such instability is certainly not unprecedented. The arrangement and behavior of mesoscale surface features was also not especially noteworthy: slowly-moving dry line/frontal mergers of the type observed occur in that region several times a year. Readily apparent gravity waves are also not uncommon in the area. Nevertheless, the fact that supercells continued to form over central Texas through much of the afternoon despite the presence of weak vertical shear suggests that some unusual circumstances were indeed coming into play. While a more conclusive answer must await careful modelling studies, it is the author's opinion that the fortuitous orientation and timing of the MCS-induced gravity wave, relative to both the slowly-moving surface boundaries and to the diurnal heating cycle, were critical in realizing and maintaining supercellular convection.

The source for the paper is directly from NOAA. I thought this would be interesting to add to the discussion (if I missed it in earlier posts, I apologize).

 

[Gabe Garfield]

I think the "compression" the author could be talking about is a decrease in the length scale of the wave (instead of a full 3D compression). In this case, the vorticity associated with the gravity wave could actually stretch and intensify (as the proverbial ice skater pulls in her arms). Definitely a poor choice of wording, though.

Aaron, I agree with what you have said, however the article specifically mentionsThis is almost completely contradictory to what you just said about about stretching (which is true). I don't know how to rectify the discrepancy. LoL.

 

[Patrick Marsh]

Gabe you're proposing that the author meant a horizontal compression versus a vertical compression?

If so, I can't visualize a gravity wave doing this...

 

[Kiel Ortega]

I'm glad Eddie posted the link to the guy's webpage with the papers...b/c the press release was laughable. The paper first paper listed on the page was decent...however, a big problem with it is that in the simulation he sends the trough first then the ridge for the interaction. Looking at the graphs, if the ridge is sent in first it looks as if the vorticity in the mesocyclone would significantly decrease and the increase later wouldn't overcome this decrease. I didn't read the entire paper (thumbed most of the examples), but I would like to see the results of his model ran that way and an example where one of these waves weakens a mesocyclone.

 

[cdcollura]

Good day all,

SPC even has a link to such events in their "Cool Images" section...

This was a hail storm that was enhanced by a gravity wave train. Tornadoes, dependant on storm updrafts, also can be influenced for obvious reasons.

Lint to SPC on this event is below...

http://www.spc.noaa.gov/coolimg/gwavecb.htm

It also seems that these waves, like more-common air-mass boundaries, can influence storm propagation as well if the supercell becomes "anchored" on them. What if a strong gravity wave and outflow boundary / dryline interact?

 

[Patrick Marsh]

This was a hail storm that was enhanced by a gravity wave train. Tornadoes, dependant on storm updrafts, also can be influenced for obvious reasons.

I don't know if you can say that the hail storm was "enhanced" by a gravity wave train when we have no idea of what the storm was like without the influence of the gravity wave. It is safe to say that the gravity wave (train) aided initiation by aiding lift necessary to overcome a strong cap, but I'm not comfortable in saying that the storm was "enhanced" by this gravity wave.

I'm also not so sure that tornadoes are influenced "for obvious reasons"...mainly because it is not obvious to me.