Dan Robinson
EF5
This may be a very interesting area of research that to my knowledge has never been done in detail. The hypothesis is that most, if not all, "tornado sized" funnels below cloud base (that is, not "shear funnels", midlevel funnels or other small transient features) have a damage-capable circulation at ground level given moderate-or-lower LCLs. That is, it would be more accurate to assume they are tornadoes than not, for all practical purposes.
A damage-capable circulation will only manifest itself to an observer at distances greater than a half-mile or so if there is enough material to loft (dirt or debris). Without anything to loft (such as over a rain-soaked field), the circulation at ground level will present at minimum with lighter debris and periodic small suction vortices. To gain a positive visual of these features, you quite literally have to be right there next to it. A spotter a half-mile away or farther will never see these, but we know they are likely there as a result of dozens of chasers making close intercepts of them.
The primary evidence to support this hypothesis comes from chasers who have witnessed and documented quite a few of these. How many times have chasers been right under a funnel and it's been observed with certainty that there *hasn't* been something at ground level? I can't think of any.
The best example I have with good video documentation is the Meredosia, IL tornado on 12/1, with emphasis on the ground-level circulation crossing the road on my front dashcam at 3:03 in the video. One of the suction vortices was no bigger than 10 or 15 feet above the ground:
I think that most funnels (again, "tornado sized", not small transient features) have *at least* something similar underneath, and I believe this might be confirmed by research if it were undertaken. A mobile home or weaker structure would be damaged or even destroyed if hit directly by such an innocuous-looking circulation, so the paradigm of always dismissing them as non-tornadic has real-world implications.
We might have 50 to 100 case studies for a paper just from chaser observations. I have at least a half dozen myself.
A damage-capable circulation will only manifest itself to an observer at distances greater than a half-mile or so if there is enough material to loft (dirt or debris). Without anything to loft (such as over a rain-soaked field), the circulation at ground level will present at minimum with lighter debris and periodic small suction vortices. To gain a positive visual of these features, you quite literally have to be right there next to it. A spotter a half-mile away or farther will never see these, but we know they are likely there as a result of dozens of chasers making close intercepts of them.
The primary evidence to support this hypothesis comes from chasers who have witnessed and documented quite a few of these. How many times have chasers been right under a funnel and it's been observed with certainty that there *hasn't* been something at ground level? I can't think of any.
The best example I have with good video documentation is the Meredosia, IL tornado on 12/1, with emphasis on the ground-level circulation crossing the road on my front dashcam at 3:03 in the video. One of the suction vortices was no bigger than 10 or 15 feet above the ground:
I think that most funnels (again, "tornado sized", not small transient features) have *at least* something similar underneath, and I believe this might be confirmed by research if it were undertaken. A mobile home or weaker structure would be damaged or even destroyed if hit directly by such an innocuous-looking circulation, so the paradigm of always dismissing them as non-tornadic has real-world implications.
We might have 50 to 100 case studies for a paper just from chaser observations. I have at least a half dozen myself.
The paper is not saying that all tornadoes form from the ground. That's pretty obvious from cases where funnels are aloft and never cause damage at the surface.
