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It's often said that waterspouts are weaker than tornadoes, but after some quick searches on the internet, I haven't been able to figure out why that is.

Two relevant sources that I've found:

  • This claims that "A difference between the two is that a waterspout tends to be weaker. The force of friction is weaker over water thus there is less air available to be drawn into the circulation." — perhaps this is clear to someone with a stronger background in the sciences than me, but I'm not sure why a weaker force of friction would lead there to be more air (if anything it seems like weaker friction would allow for more air to flow?)
  • This source matches my intuition and claims the opposite reason: "In general, waterspouts are not as strong as tornadoes, in spite of the large moisture source and the reduced friction." but then doesn't explain why tornadoes are stronger

So what makes tornadoes stronger?

Thanks in advance!

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Part of it is due to friction. You can see in this video of a landfalling waterspout the influence that enhanced friction has on tightening the circulation. So, like the ice skater analogy, enhancing the inflow tightens the circulation by conserving by the conservation of angular momentum.

Another thing to consider is that fair weather (non-tornadic) waterspouts are fairly common when it comes to waterspouts, whereas landspouts are uncommon in comparison, as mesocyclones generate preferentially over land. This means that tornadoes (not landspouts) have access to extra buoyancy over land (more convection=more severe storms= more violent tornadoes).

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  • $\begingroup$ Thanks! The friction -> tightened circulation/moment of inertia link was the missing link for me. Great choice of videos too! $\endgroup$ Aug 25 at 3:36

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