1. Why Not Look Only at Model Output?

5. Comparison of Various Forms of the Q-G Omega Equation
Classic (Two terms: differential vorticity advection, Laplacian of the thermal wind)
The result is the difference between two large terms resulting in large truncation error.
Cannot estimate reliably from vorticity advection at a single level or from warm advection alone.
Using at a single level, best done at 500 hPa for strong events. Really need a 3D solution for an accurate answer.
Trenberth/Sutcliffe formulation (advection of absolute vorticity by the thermal wind) is more accurate since no cancellation problem.

6. Q-Vector approach is the best in many ways
No cancellation problems
Includes deformation term
Provides insights into the lower branch of the ageostrophic circulation forced by the geostrophic forcing
Provides insights into frontogenesis
Allows rapid and intuitive graphical interpretation

7. QG Diagnostics Online
Classic approach:
Sutcliffe-Trenberth:
Q-vector

8. Vertical Motion Can be as the complex sum of:
QG motions (relatively large scale and smooth)
Orographic forcing
Convective forcing
Gravity waves and other small-scale stuff
QG diagnostics helpful for seeing the big picture

9. Jet Streak Vertical Motions

11. For unusually straight jets, it might be reasonable

12. But usually there is much more going on, so be VERY careful in application of simple jet streak model
Garp example…

15. The END

23. The end