• form of equation:
  (- P_sfc tend.) ~ (Abs. vort. advection at 500 mb) + (thickness advection by sfc wind)
• PVA => P falls, NVA => P rises
• WAA => P falls, CAA => P rises
• notes:
  1. sign of P change ambiguous where T advect. opposes vorticity advect.
  2. for intensification: PVA above sfc low center. This implies that upper vort. max (and thus the upper trough) must be upstream from the sfc low.
  3. T advection greatest on cold air side of the fronts
  4. From T advection, expect sfc H to move in SE direction, expect sfc L to move in NE direction. So the H and L paths diverge.
  5. The paths parallel to thickness (h) contours.
     • h contours look similar to 500 mb Z contours.
     • leads to notion of steering level based on 500 mb flow
     • empirical rule: developing sfc system moves in direction of 500 mb flow but with 1/2 the speed.
  6. motion at 1 level is linked to other levels
• Example of cyclone development See fig. 4.3

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