• Section 1: Baroclinic Equivalent Barotropic Vorticity eqn (BEBVE)
  • improves upon EBVE by including an approximate thermal wind
  • Note: thermal wind def here is relative to the vertical mean, that is not the "conventional" definition that you find, say, in Holton's textbook.
  • result is additional parameters: thermal wind V_T and thermal vort.
  • BEBVE has term not in EBVE that is advection of thermal vort. by V_T.
  • the new term can cause development if the thermal vort max is upstream from the vort. max. In that case there is positive thermal vorticity advect ("PTVA") where the vort. is max so that the max vort. can increase
  • schematic diagrams where shown to illustrate offset of h and Z fields at various levels.

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• Section 2: upper level changes
  • mainly consult Fig. 7.6
  • examples of shape changes:
    1. migration of jet streak & vort. max from SW to SE and E side of the trough. Initially trof axis is SW-NE which becomes more NW-SE orientation.
    2. Pinching off of a "blob" of colder air leading to formation of a closed low.
  • vorticity & h advection. Consider this timeline of events just west of the sfc low:
    1. initially, upper PVA exceeds the CAA since sfc circulation is weak but upper trough is not.
    2. that upward motion may be too dry to condense despite the lifting.
    3. as sfc low intensifies, CAA gets going and overpowers the PVA and air parcels sink. The CAA also leads to falling thicknesses, and so the Z contours fall as well.

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• Section 3: Coupled upper and lower development
  • mainly follows Fig. 7.7
  • development doesn't start until features favorably aligned
  • note relevance to fig. 7.6 and BEBVE terms.

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