What are the sizes of the objects that could be picked up and flown by tornados, depending on the tornado's speed?
To put it another way, assuming turbulent flow and object density much higher than that of air, what is the dependency of the maximal size of the flying object on the speed of the wind around it? Assume the objects are of similar shapes and densities.
My naive estimate is like this: denote characteristic size of the object $l$, denote wind speed $v$, then the weight of the object $mg=const\cdot l^3$, and the force of the wind $f=const\cdot l^2\cdot v^2$. Therefore $l\sim v^2$. Is this estimate correct for the above conditions?