Cyclical supercells and curved damage paths?

[David Rundle]

Just a quick question: Is there any correlation to the observed damage path and it's curve to the left of the damage path in cyclical supercells vs storms that only spawn one touchdown?

I've noticed in several examples of damage paths, May 99 OKC F5, Greensburg, KS EF5, etc, of the damage path curving to the left as they rope out. (Due to RFD undercutting?) Shortly thereafter, the next funnel in sequence develops to the NE. (same RFD tightens rotation in the new updraft?)

With single path storms, the damage path is typically consistent with the direction of the parent storm, in a linear fashion.

 

[Jeff Duda]

Ugh...*sigh*, I hate to bring up anything relating to what a certain person tried to get us all to believe a few weeks ago relating tornado patterns...but...

I think this is a case of tornado paths following that of a cycloid, which is a path traced out by a fixed point on a circle as the circle translates in a straight line. In the article by Brown and Knupp (1980) called The Iowa Cyclonic-Anticyclonic Tornado Pair and Its Parent Thunderstorm (available at this URL: http://ams.allenpress.com/archive/1520-0493/108/10/pdf/i1520-0493-108-10-1626.pdf), they talk about how the tornado took a hard right turn and how that might be due to the fact that the tornado itself was revolving around the parent circulation (call it the tornado cyclone or mesocyclone...I don't think they specify), and the tornado hit a critical point on the cycloid that caused the sudden hard right turn. That might explain the tornado paths when cyclic supercells spawn tornadoes. Check out the picture at this URL: http://www.antique-horology.org/_Editorial/EarlyPendulumClocks/Images/CycloidAnim04.gif. Just flip the baseline so that the circle rolls under the line (thus counterclockwise) and rotate the line counterclockwise about 45 degrees, and you might be able to see the pattern of tornadoes revolving around another circulation as the circulation itself moves northeast.

 

[David Rundle]

Thanks - I wasn't familiar with the concept of a cycloid, so this is new. Is there a reason why all paths don't follow the cycloid shape? Duration too short?

I missed the other discussion, and I don't want to beat a dead horse, but give me an idea of where this was coming from, please.

 

[Joey Ketcham]

I missed the other discussion, and I don't want to beat a dead horse, but give me an idea of where this was coming from, please.

No, let's not go there again. Please. We were doing fine.

 

[David Rundle]

I learned about the past bogus threads - agreed, better off dead and buried!

Getting back to the posting, it appears that the curved path is a function of rotation around a larger axis. So, fronts curve around lows, supercells rotate around mesocyclones, as do some tornadoes, satellite funnels rotate around parent funnels, and suction vortices rotate around inside the funnel... So...

Is it reasonable to theorize that the curve of the cycloid damage path is somehow proportional to the diameter and rotational strength of the mesocyclone?

Reminds me of something I read: "Big whirl have little whirls that feed on their vorticity. Little whirls have smaller whirls, and so on to infinity."

 

[Chris Nuttall]

Just a quick question: Is there any correlation to the observed damage path and it's curve to the left of the damage path in cyclical supercells vs storms that only spawn one touchdown?

Yeah, this can be a common occurrence with cyclical supercells. I almost observed it on 4/29/09 near Panhandle, TX. The new tornado did not hold together long enough to fully complete the cycle. Then again, I wasn't dealing with a long-track tornado either. I've got some video of it on my website:
http://www.stormkiller.com/componen...2_GALLERYSID=e8c74b30f6e7f44ae7eb2088dd0bfbc2

I couldn't recite the theories surrounding the physical process without looking them up, but it's basically a by-product of the old tornado occluding while the next one develops. I used to have a great overlay of the Greensburg damage path for Google Earth, but I'm not sure where it is now. If you notice in that path, the first tornado occludes, with the damage path forming a comma shape. This is a typical structure seen in mature, synoptic-scale extratropical cyclones. After seeing it on the larger scale, I'm not surprised in the least to see it on the mesoscale with strong tornadoes and cyclical supercells.

When the mesocyclone is cycling like this, the new tornado/area of rotation usually starts to develop on the SW flank of the old one. You'll sometimes see two hooks in the reflectivity. If it can take hold and maintain itself, you'll see it touch down to the E of the old tornado because as the old one dissipates, it will usually get ingested (recycled) back into the new meso/tornado. You can kind of visualize this if you think of the remnants of the old meso rotating into the new, and following up the path into the new tornado.

I apologize if I wasn't very clear. This is one of those things that's easier for me to explain with graphics and speech, and not with text.

 

[Kiel Ortega]

Just a quick question: Is there any correlation to the observed damage path and it's curve to the left of the damage path in cyclical supercells vs storms that only spawn one touchdown?

I think there is something to be said here of the damage surveys which are conducted on the tornadoes: you are at their mercy. If the survey is good enough, you may find the left turn or the circle as was present in Greensburg. If not, maybe you notice a right turn! I think it is of note that most tornadoes are not surveyed, so the left turn may not be of significance. I know of a couple tornadoes in 2008 which turned right (or at least were reported to do so) at the end of the damage path, which might be of some significance. Further, a detailed survey of the Norman, OK, tornado in June revealed a circle turn like that present in the Greensburg tornado and the Norman tornado was a fairly small tornado. So I issue caution to ANYONE trying to read anything from tornado paths/locations: you are at the mercy of the verification data and it has been shown that even U.S. storm verification data is really not all that great.

 

[David Rundle]

I agree that survey information is not always complete, but significant events in populated areas with media exposure tend to be fairly accurate.