Tuesday, December 11, 2012

This Digging Trough Is a Tease

The loop below shows a beautiful cold front and upper-level trough migrating through the long-wave ridge over the eastern Pacific with a path that would seemingly take it to the Wasatch Mountains.  A powder dump is coming right?

1200 UTC 10 Dec – 2100 UTC 11 Dec 2011 IR and 500-mb
geopotential height analysis
Wrong.  This is a digging trough that it is amplifying and moving strongly southward along the Pacific coast.  It then slides across northern Mexico and the southwest U.S.  The frontal precipitation moving into the Pacific Northwest today stalls and decays just upstream of Utah, leaving us with just a few scraps.
GFS 500-mb geopotential height and 6-h accumulated precipitation analyses
valid 0000 UTC 12 Dec – 1800 UTC 14 Dec 2012
This is a fairly common track for storms during the cool season.  These troughs are a tease for Utah, but the southwest needs to get their share from time to time.

1 comment:

  1. How much of the digging of this trough do you think is related to the high terrain of the western U.S., and how much simply to the surrounding synoptic-scale environment? This seems to me like a case where the terrain (especially the Sierra Nevada Range) may be having a large impact on the overall track of the system.