|
|
 |
|
|
|
|
|
|
|
|
|
Storm Season is upon us. Each year at this time, storm chasers study the MRF and other model output hoping to see "THE PATTERN" that will guarantee successful chase trips. Early spring patterns can be somewhat easy to judge, with the well-marked short wave troughs and strongly "dynamic" systems marching from west to east across the country.
However, as the earth revolves towards the solstice, the midtropospheric controls become more subtle. Those individuals used to applying simple rules of thumb in making their judgements (pva=forcing for upward motion) can get into big trouble. [See Chuck Doswell's excellent discussion of this issue]. Patterns that might suggest an obvious outbreak produce "bust" chases and patterns that suggest down days may produce the most spectacular storms.
Those familiar with the full spectrum of synoptic-scale forcing might think about lower level warm advection patterns and how these can "overwhelm" the forcing associated with the more traditional view that midtropospheric pva/nva control the nature of the synoptic scale vertical motion.
There are other problems with this reasoning. [Confusing synoptic-scale lift (layer lift) with the lift that brings air parcels to their "level of free convection" is one example. Eventually links will appear here to other sites on the WWW in which these are discussed.]
Anyway, to illustrate the fact that the 500 mb/absolute vorticity pattern IN AND OF ITSELF tells one very little about the potential for tornadic supercells, I offer the following short game.
The 500 mb charts below were "lifted" from the NSSL VORTEX Operations Web Site.
|
|
|
|
|
|
|
|
|
|
|
|
