What exactly is a "Wind Feature"? Does anyone really know?

I think I first heard this term thrown about as one being responsible for the deaths of Samaras et al on 31 May 2013 at El Reno. It seems to be trying to describe something that is smaller-scale even than the individual suction vortices within a multiple-vortex tornado.

Another place I've seen the phrase several times is on Max Hagen's Extreme Planet blog. http://extremeplanet.me . His analyses of many historical and recent violent tornadoes make for fascinating reads. He uses the term in many of his posts to explain the most extreme instances of damage within a violent tornado's path. He also posits that while the EF-scale was developed under the assumption that the old Fujita scale overestimated the wind speeds required for complete destruction of a home, many violent tornadoes do in fact contain winds in excess of 300 MPH, at least for brief bursts within these "wind features." So that naturally raises some questions in my mind:

What exactly is the nature of these "wind features"? Is it just another name for an individual vortex of a multiple-vortex tornado, or is it indeed something smaller-scale yet?

Are they necessary to produce the type of extreme damage that defines a violent tornado? If so, what is it about the parameters that we consider favorable for violent tornadoes (shear, instability, etc) that makes the occurrence of these "features" more likely? Also if so, what is the maximum damage a tornado can inflict without the presence of these "features"? EF3? Low-end EF4?

Is there any way to predict the occurrence of these "features" within the path of a tornado? Are they related to supercell/mesocyclone intensity at the time or dependent on influences like topography? Who can say at any given point during its path whether a large, long-track and dangerous-looking tornado existing within high-risk type parameters will "merely" rip the roof and exterior walls off a well-constructed home, or rip the anchor bolts right out of the foundation, launch whole railroad cars or similarly heavy industrial machinery a quarter-mile in a single toss, kill people even if they were in the basement, et cetera.

Is there a particular subcategory of violent tornado environment that makes the occurrence of these "features" more or less likely, or makes them more or less intense? Extreme shear and moderate instability with tornadoes moving 50-70 MPH in the two super outbreaks, vs. modest shear and extreme instability with very slow-moving tornadoes (The Jarrell, TX event, which Hagan cites as producing the most extreme tornado damage of at least the last 44 years based on the complete destruction of the Double Creek subdivision in Jarrell and the 0% aboveground survival rate in same), vs. something in between (say, the Pilger area EF4 family of this year)?

Thoughts?
 
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