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Thread: Tornadogenesis

  1. #1 Tornadogenesis 
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    The following is an hypothetic chain of events, involving known natural forces, that could cause a tornado. Any comments, whether in the whole or any part of it will be appreciated.
    The starting point is a supercell thunderstorm, because it is known that it provides the conditions for tornadogenesis:

    1. Warm air inside a supercell thunderstorm rises as water vapor.
    2. Above the cooler air, the water vapor condenses into water droplets.
    3. Not massive enough to be pulled down by gravity, the water droplets stay hovering and continue to freeze into tiny ice crystals.
    4. Due to the surrounding humidity, the ice crystals become more massive and
    start descending at a very slow terminal velocity.
    5. Captured by the coriolis effect, the descending ice crystals start rotating to eventually create a mesocyclone.
    6. Attracted by the centripetal force towards the center of rotation, billions of falling tiny ice crystals stick together due to the cohesive force.
    7. If the timing is right, a huge massive accretion of ice builds up along the center of rotation in a matter of seconds.
    8. If more than one accretion of ice is built up around the center of rotation, a multiple vortex tornado may form.
    9. Pulled by gravity, the massive accretion of ice start falling, growing bigger and bigger, as it encounters, jams, and brings down lower layers of ice crystals.
    10. The now gigantic accretion of ice, free-falls from altitudes between 15,000 to 30,000 meters accelerating at 9.8 m/sec per sec.
    11. A vacuum trails the falling object.
    12. As a giant piston, the atmospheric pressure finds the path of least resistance top-to-bottom, jamming down a column of air to fill the vacuum.
    13. The air rushing in, is always the less dense air coming from above as oppose to the denser humid air, from the sides (from the cloud.)
    14. The atmospheric pressure headed to 100,000 newtons per square meter combined with the coriolis effect siphons a spiraling downburst creating a vortex.
    15. Eventually and due to friction, the falling accretion of ice disintegrates into hail that is scattered around the vortex. Then the centrifugal force takes over keeping the vacuum that powers the system from inside the vortex.
    16. If the resulting system is powerful enough, it reaches the bottom part of the supercell becoming visible in the form of a funnel.
    17. If a touch-down occurs, a tornado forms.
    18. The downburst hitting the ground squeezes out underneath the sides of the vortex, allowing the atmospheric pressure to continue siphoning down air from above.
    19. The tornado will continue for as long as the equilibrium of forces at play, maintains the air rushing into the vortex from above, otherwise it dissipates.


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    • #2 Re: Tornadogenesis 
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      Quote Originally Posted by Ramon Zuniga
      The following is an hypothetic chain of events, involving known natural forces, that could cause a tornado. Any comments, whether in the whole or any part of it will be appreciated.
      The starting point is a supercell thunderstorm, because it is known that it provides the conditions for tornadogenesis:

      1. Warm air inside a supercell thunderstorm rises as water vapor.
      Ok good so far.

      2. Above the cooler air, the water vapor condenses into water droplets.
      3. Not massive enough to be pulled down by gravity, the water droplets stay hovering and continue to freeze into tiny ice crystals.
      2. is good enough. 3. Well it's a bit more interesting. Usually the droplets continue to rise until they are supercooled water. It takes a fussion condensation nuclei to set off the freezing, and once the first droplet freezes, almost all the remaining water goes towards those frozen droplets.

      4. Due to the surrounding humidity, the ice crystals become more massive and start descending at a very slow terminal velocity.
      The get larger and also collide and adhere to each other--in layman's terms they become snow flakes. Unless their in the immediate strong updraft they'll usually start to descend.

      5. Captured by the coriolis effect, the descending ice crystals start rotating to eventually create a mesocyclone.
      If over a large enough area (because Coriolis effect is tiny otherwise), that would create an anti-cyclone. I'll stop there and let you think about it.


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    • #3  
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      Thank you Lynx_Fox for your comments.

      I think I got your point: If the rotation results from the coriolis effect, it has to be contrary to the rotation of earth or anticyclonic. And, a mesocyclone is cyclonic.

      If you think it is worthwhile to continue the analysis of the remaining points, let's re-word the point 5 as follows:

      5. Captured by the coriolis effect, the descending ice crystals start rotating to eventually create one or more vortexes.

      (This implies that regardless of the mesocyclonic rotation of the supercell, it is possible to generate one or more vortexes due to the coriolis effect inside the supercell.)
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    • #4  
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      Quote Originally Posted by Ramon Zuniga
      Thank you Lynx_Fox for your comments.

      I think I got your point: If the rotation results from the coriolis effect, it has to be contrary to the rotation of earth or anticyclonic. And, a mesocyclone is cyclonic.
      Yes. To add further Coriolis acceleration for descent is extremely small, too small compared to other forcing. What makes it tend towards anticyclonic is the cool high pressure dome it will produce.

      Interestingly you've stumbled into one of the conditions to maintain a supercell, this dome must offset the rising air or it kills the storm. This happens in high convective instability with small wind share--and leads to pulsing convective storms. Sustained supercells need the right combination of vertical wind share and stability.
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