Ordinary Cell:

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Ordinary Cell
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Multicell
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Supercell
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Physical processes controlling cell types

• Buoyancy processes basic updraft/downdraft,
  (ordinary cells)
• Gust front processes triggering of new cells,
  upscale growth, (multicells)
• Dynamic processes rotating updraft, dynamic
  vertical pressure gradient forcing, (supercells)

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Buoyant Processes
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Density Current
Theoretical speed of propagation
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RKW Theory Rotunno et al. (JAS, 1988)
C/?u gt 1
Optimal condition for cold pool lifting
C/?u 1
C/?u lt 1
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Vortex Tube
Circulation
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Dynamic Pressure Effects
(take divergence)
diagnostic pressure eq.
Dynamic pressure
Buoyancy pressure
Vertical momentum
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Updraft growing in sheared environment
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For a wind field in pure rotation
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Supercells propagate to right and/or left of the
mean vertical wind shear vector
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Supercell Hodographs
Supercell processes are Galilean invariant!!!
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Bunkers et al. WAF 2000
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Helicity
Actually, Streamwise Vorticity
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Swirl Ratio S Vo / Wo
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Vortex Tube
Circulation
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