the perfect map for the perfect storm ?

[Stephen Locke]

Conventional wisdom says something like this "see a big trough is hanging out over the west coast ejecting short-wave troughs into the plains and eventually ejecting itself . . . "

Question; Does anyone have samples of, day 5, day 4, day 3, 2, 1, NOW, maps of systems that produced significant weather events on the plains?

 

[Andrew Herron]

I saw this too coming up, right now on GFS it looks like a 10/10 arrival and quite strong too. I also noticed a low swooping over Michigan around next Tuesday. I too would love to see some maps of a similar setup, I'm looking up 10/18 of last year right now which looks very similar.

 

[Tim Vasquez]

Well, one caveat is that powerful weather systems can completely overwhelm the pre-storm environment and produce linear squall lines. Quite often the best chase days have a delicate balance of seemingly "marginal" ingredients at the synoptic scale with the lower troposphere showing exceptionally good shear and helicity. The May 3 outbreak charts would be a good starting example:

http://www.wxhistory.com/wiki/May_3,_1999

Tim

 

[Andrew Herron]

Perhaps someone who can read these better (Mr. Dale?!) and explain what difference and what similarities there are. They're both 14 days out from the 'event' and while they are different, they appear to be somewhat similar. I know we should be looking at more, but do you vets suggest?

http://www.met.sjsu.edu/weather/archive/GFS/1007/500/500mb-20071004-00z.gif

http://www.met.sjsu.edu/weather/archive/GFS/0908/500/500mb-20080925-00z.gif

 

[Fred Gossage]

Well, one caveat is that powerful weather systems can completely overwhelm the pre-storm environment and produce linear squall lines. Quite often the best chase days have a delicate balance of seemingly "marginal" ingredients at the synoptic scale with the lower troposphere showing exceptionally good shear and helicity. The May 3 outbreak charts would be a good starting example:

http://www.wxhistory.com/wiki/May_3,_1999

Tim

Strongly agree with this, and your mention of this in your textbooks is what got me researching trough amplitude and tilt in severe outbreaks here in the Southeast several years back, Tim. Most of the BIG tornado days, especially east of the I-35 corridor, happen with broad-based troughs, versus the large...sharp, high-amplitude troughs. These often have too much lift associated with them, and either a solid squall line or messy convection results. And for areas east of the Ozarks to Upper Texas Coast, several of our significant tornado outbreaks occur with neutral or even negatively tilted troughs. We usually aren't capped nearly as strong as in the Plains, and if we have too much lift over a large area, BOOM... messy radar scopes. I've also noticed that all four F5 tornadoes in Alabama state history occurred in the right-front quadrant of the main upper-jet streak. As you've said over and over, the insane dynamic days (especially in the fall, winter, and early spring months) can really ruin a chase day or violent tornado day... and this is even more true for areas east of the Plains.

 

[Bobby Prentice]

Question; Does anyone have samples of, day 5, day 4, day 3, 2, 1, NOW, maps of systems that produced significant weather events on the plains?

Great places to search are:

NSSL/SPC Weather Event and Case Study Catalogue Page

John Finch - Historical Tornado Cases for North America

 

[Brian Stertz]

Some of the best events I can remember have a strong frontal passage about 24-36 hrs. before the inbound trough begins to move out into the Plains. The timing is such that the strong EML cannot advect across the main body of the Plains and cause troubles with daytime development of intense sfc based supercells. I like the best setups when a strong cap is across OK/TX along and south of I-40, and the surface warm front and triple point are across C/S Kansas or N. Oklahoma. Those days historically have been HUGE events through the years.

 

[Bobby Prentice]

Here is a great set of charts and analysis for the biggest tornado outbreak of all time:

Tornado Outbreak of April 3-4, 1974; Synoptic Analysis (pdf format)