• After witnessing the continued decrease of involvement in the SpotterNetwork staff in serving SN members with troubleshooting issues recently, I have unilaterally decided to terminate the relationship between SpotterNetwork's support and Stormtrack. I have witnessed multiple users unable to receive support weeks after initiating help threads on the forum. I find this lack of response from SpotterNetwork officials disappointing and a failure to hold up their end of the agreement that was made years ago, before I took over management of this site. In my opinion, having Stormtrack users sit and wait for so long to receive help on SpotterNetwork issues on the Stormtrack forums reflects poorly not only on SpotterNetwork, but on Stormtrack and (by association) me as well. Since the issue has not been satisfactorily addressed, I no longer wish for the Stormtrack forum to be associated with SpotterNetwork.

    I apologize to those who continue to have issues with the service and continue to see their issues left unaddressed. Please understand that the connection between ST and SN was put in place long before I had any say over it. But now that I am the "captain of this ship," it is within my right (nay, duty) to make adjustments as I see necessary. Ending this relationship is such an adjustment.

    For those who continue to need help, I recommend navigating a web browswer to SpotterNetwork's About page, and seeking the individuals listed on that page for all further inquiries about SpotterNetwork.

    From this moment forward, the SpotterNetwork sub-forum has been hidden/deleted and there will be no assurance that any SpotterNetwork issues brought up in any of Stormtrack's other sub-forums will be addressed. Do not rely on Stormtrack for help with SpotterNetwork issues.

    Sincerely, Jeff D.

Path deviations

Joined
Jul 2, 2014
Messages
50
Been reading some papers on terrain effects on the near surface tornado structure the (corner flow region). I’ve came across numerous times that some tornadoes will deviate from the general forward motion. Can anyone explain this? Does it have anything to do with a change in swirl ratio?
 
I can't profess to be able to answer question as I think that the low-level wind flow into tornadoes is still rather poorly understood. Having said that, overall I would suggest that a tornado's motion is generally governs by a couple of factors: the parent updraught's motion; and interaction with low-level outflow/gust fronts. Tornadoes can also rotate about the parent mesocyclone, probably due to the latter.

So all I can suggest is that low-level flow which is being affected by terrain is going to have some implication to how it arrives at the tornado, which could, in turn have an effect on its motion - or, at least, the motion of its base.
 
Does it have anything to do with a change in swirl ratio?

Swirl ratio determines a vortex's structure; from single-cell, to two-cell, to multi-vortex. I don't believe it has any direct implications on the motion, although an increase in the swirl ratio will cause an increase in the size of the vortex, which may cause the vortex to appear that it's changing direction.
 
I wonder if an appeal to potential vorticity would shed some light here. If a tornado moves uphill the vortex will compress vertically, which due to conservation of potential vorticity should (if I remember my dynamics correctly) cause the vorticity to decrease (although I may have that exactly the wrong way). The change in vorticity could possibly then lead to a course deviation somehow, but the exact mechanism escapes me as of this moment.
 
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