Probably like many of you, I like negative vorticity advection, or "NVA" for short. When a ridge of high-pressure builds in over your area bringing sunny/breezy pleasant days after an especially nasty front passes by, chances are you can find a blob of NVA somewhere in your vicinity at around the 500MB level (about 18,000 ft in the mid-latitudes). Well, on a weather chart I mean... Negative vorticity at 500mb, a measure of negative or anti-cyclonic spin, is a good indicator of downward vertical motion in the mid-levels of the atmosphere, which will often translate into fair skies and pleasant days for awhile. PVA (Positive Vorticity Advection) is NVA's nasty older brother, who loves to bring the pain--cyclonic-turning, upward-lifting, scary organized bad-weather patterns with maybe a nice pre-frontal squall line of severe thunderstorms thrown in for good measure. Run for the storm cellar!
One of my blog categories is "Weather Related", which hasn't been getting much attention lately, due to my darn gadgets and my laziness, but it's high-time to update the darn thing, so that's what I did. Luckily for you, you don't need to locate the NVA, or PVA to use these awesome/free on-line services, but if you want to try, here's a link to the NWS NGM model forecast upper-air charts. Tell ya what...You locate the PVA areas correctly in this 500MB vorticity chart (not much strong, organized PVA/NVA this time of year in the N. Hemisphere), and I'll... I'll declare you an honorary SP & PPC magazine forecaster geek extraordinare, or something. Or, maybe, I'll just give you some more cool weather links to check out instead...
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