Henry, W. K., 1978: The Southwest Low and "Henry's Rule." Nat. Wea. Dig., 3(1), 6-12.
Here is the Eta model forecast of 500-mb heights initialized at 1200 UTC 23 October. Note the kicker coming in off the Pacific Ocean to displace the cut-off over the southwest U.S. (kickee). Note that the kickee starts moving when the kicker is approximately 20 degrees of longitude upstream (at 40 degrees N, about 2000 km)---nicely in agreement with Henry's Rule.
Here is the geostrophic advection of the geostrophic absolute vorticity at 500 mb overlaid on the 500-mb heights at 60 h.
Here is the geostrophic advection of the potential temperature at 500 mb and 850 mb.
Greg Hakim defends PV thinking.
Mike Baldwin on evaluating QG theory from models.
REVISED CALCULATIONS
With Mike Baldwin's comments in mind, I filtered the Eta-model height
grids using the methodology of Schultz and Doswell
(2000, WAF) with lambda = 5*sqrt(2). Then the two terms in the
right-hand side of the QG height-tendency equation (differential
thermal advection and geostrophic vorticity advection) are computed
from the filtered grids.
Animation of 500-mb unfiltered heights
Note that the 300-mb vorticity advection term is about an order of
magnitude larger than the other terms, thus suggesting its importance.
One of two calculations would need to be done next: (1) inversion of
the "Laplacian" in the QG height-tendency equation, (2) PV inversion
of the flow induced by the two shortwave troughs (Hakim et
al. 1996, MWR).
If anyone is interested in taking this project further, please
contact me
(david.schultz@noaa.gov).
Last update: 16 November 2000
Animation of 500-mb filtered heights
Animation of 300-mb vorticity
advection term
Animation of 500-mb vorticity
advection term
Animation of 200-mb differential thermal
advection term
Animation of 500-mb differential thermal
advection term
Animation of 850-mb differential thermal
advection term
