Fastest Tornado Forward Speed

[calvinkaskey]

During the superoutbreak on April 27,2011 some of the cells and or tornadoes were moving 70 mph or more. Here is one that is you look at how much of the view it covers even before the camera is zoomed in it is about 75 percent or so of the horizontal view in only 51 seconds. https://www.youtube.com/watch?v=zEr2lCnQcow&list=WL&index=22


Given a 2 mile wide base for the mesocyclone [tornado along with stratus] and that it covered basically all the screen in the video and the tornado traveled about 75 percent of the screen width in 51 seconds the forward speed could be about 100 mph. This is dealing with the video I linked above. I'm listing this comment separately because the number seems kind of crazy.

 

[Paul Knightley]

Very interesting thread, and some great insights/thoughts - as well as Skip's great initial post.

It begs wider thoughts on the way 'we' (as human beings) try to classify things around us, in this case, atmospheric vortices. Just because we want to compartmentalise a violently-rotating column of air associated with deep, moist convection, a 'tornado', is irrelevant to the way the atmosphere works.

There must be (at least) two key larger-scale processes governing the velocity of a tornadic circulation:

1) The forward speed of the parent supercell, and the associated low-level mesocyclone;

2) The velocity of the low-level wind field around the mesocyclone, and associated inflow/gusts fronts.

Number 1, to a greater or lesser degree, dictates the overall velocity of the tornado 'threat' (i.e. how quickly the area of interest/danger/whatever) moves towards a town, or person, or whatever. In some case, a tornado associated with this (especially a large one) may 'move' at a reasonably similar forward velocity.

Number 2, to a greater or lesser degree, dictates the velocity of the tornado at a very local level - for example, we know that sometimes tornadoes rotate around the parent mesocyclone, meaning the forward velocity is a product of both the mesocyclone's forward velocity, and its rotational velocity.

Thus, when we see reference to historic tornadoes having high forward velocities, I suspect in many cases this is due to a high forward velocity of the parent storm, because folks weren't generally looking in fine detail...I suspect many of these are not referring to tornadoes racing around in the mesocyclone (as in the case Skip has highlighted).

 

[Skip Talbot]

Bumping this thread because there's been new work and revelations on this event. My colleagues Hank Schyma and Anton Seimon revisited the case, and refined some of the earlier estimates. Josh VandenTop's video was included, along with my and Hank's own shots, and Rob Hurke's to produce a precisely measured and timestamped track of the fast moving rope. A summary of the major take-aways:

• Maximum forward speed was measured at 94.6 mph over a duration of 5.33 seconds
• Damage scars in aerial imagery indicated a continuous path identifying the fast moving tornado as the Pilger EF4
• The track is mostly straight line in the minutes leading up to dissipation, not curving around the Wakefield EF4 as its satellite or subvortex, suggesting the vortex was independent of the larger developing tornado

The latter point was the most surprising finding to me, as I long assumed the fast moving rope was orbiting Wakefield, and that its remnants may have even merged into Wakefield. However, the measured track and a closer examination of extended footage show this not to be the case. The dissipating Pilger EF4 appears to track with, run into, and stall on the apex of the storm's RFD gust front. I suspect that an intense surge of RFD is the driving mechanism for the rapid acceleration of the Pilger EF4, and not that it became entrained in the Wakefield circulation.

The work is detailed along with other infamous fast movers in Hank's latest production: