Forecasting Using Surface, 850, 700, 500, 300, 200mb charts?

[Keith Mullen]

Couldn't we just all ask Mike H. really, really nice, "Please Mike! Could you be so kind as to produce "Storm Structure & Forecasting 201" ?"



I'll be your friend if you do!....

 

[Jeff Duda]

Careful! PVA doesn't equal upward vertical motion!

I never actually said PVA = UVV, however I can see how my implication may have led you to believe I said that. I agree, though, that PVA may not imply upward motion if other factors that promote downward motion, such as CAA, upper level convergence, or low level divergence, exist and are forceful enough to negate any upward motion that PVA tries to generate.

 

[Shane Adams]

Forecasting (as it applies to chasing) can be gleaned from a book, but it has to be applied in the real world to make any sense of.

Look at it this way: The book reading is the VORTEX project in 1995. Actually learning how to apply it and use it for successful chasing, that's the research that is still ongoing from that VORTEX project.

There is no "overnight" when it comes to learning how to chase and forecast. I'd imagine people are pushing you to read certain websites because you'd get the same information whether they tried to explain it to you on here, or whether you just went a read it for yourself. Plus, neither method is going to teach you anything you'll be able to apply (and understand) in the field for at least 2-3 years, depending on how much you test it per season.

All newbies: Don't be afraid to fail. Don't be afraid of ignorance. Those things are at the starting line for anybody who wishes to learn this stuff. All it means is you've chosen to start the journey. It doesn't happen in a few days, weeks, months, or even years in some cases. You just wake up one day and realize you know some stuff, and it just snowballs from there.

 

[Patrick Marsh]

I never actually said PVA = UVV, however I can see how my implication may have led you to believe I said that. I agree, though, that PVA may not imply upward motion if other factors that promote downward motion, such as CAA, upper level convergence, or low level divergence, exist and are forceful enough to negate any upward motion that PVA tries to generate.

So, since we are in the advanced section, I'll go ahead and say it.

PVA, at a level by itself, NEVER implies rising motion...contrary to what is said on the forums. The correct expression is: where DPVA is positive, you tend to have rising motion.

DPVA is defined to be differential positive vorticity advection. In other words you have to have increasing vorticity advection with height. You can have negative vorticity advection at 500mb and still having rising motion - if you have greater NVA beneath it. By the same token, if you have PVA in the mid-levels and greater PVA beneath it, you'll end up with sinking motion.

(The reason people can get away with saying PVA at ~500mb yields rising motion is because they implicity make the assumption that PVA is ~0 at the surface. You can get away with this because of the tendency for low pressures / height systems close to the surface to be closed, or circular. In this situation, vorticity is advected around the storm system, along lines of constant vorticity, yielding vorticity advection equal to 0. Plus, winds are considerably weaker at the surface...so advection is less than if you had stronger winds.)

DPVA is the correct term to use.

 

[Mike Hollingshead]

Couldn't we just all ask Mike H. really, really nice, "Please Mike! Could you be so kind as to produce "Storm Structure & Forecasting 201" ?"



I'll be your friend if you do!....

A wise person that knows all about forecasting(certainly not me) would be smart to make such a dvd. Thought someone had talked about making one in chat. Thing would sell, even to people that don't have much desire to chase.

 

[mikegeukes]

Someone like Tim Vasquez, would do a excellent job in making a series of Analysis and Forecasting DVD's.

 

[Keith Mullen]

Thanks Mike & Mike.

Yes, it would sell like hotcakes.

Understanding all the ingredients & "players" that come together to create ideal conditions for severe weather is one thing. Understanding what is occurring at the time of storm initiation & what is occurring within a storm is another...

...but trying to really wrap one's brain around timing, short waves, exactly when and where all the ingredients are most likely to meet & cook something up - forecasting - is difficult to grasp at best by rookies like myself (particularly when all you have is written text).

Structure & Forecast 201 - with comprehensive glossary? Any takers out there?

** ; )

 

[Jeff Duda]

PVA stands for positive vorticity advection, which simply means the horizontal transport of air with higher vorticity into a region with lesser vorticity; this must occur in the mid-upper levels to generate upward motion.

Patrick,
You are exactly right on the PVA argument. I was indeed making that assumption when I said that. I kind of alluded to it in the quote. But yes, what you say is 100% correct.

 

[Darren Addy]

While I'd agree that reading all of Haby's Hints (theweatherprediction.com) is certainly good advice for anyone interested in weather, I think we would also agree that Haby's Hints was not written with severe storm forecasting as its only focus. It occurs to me that what might be a helpful "bridge" for people coming to weather through an interest in severe storms might simply be a Table of Contents (list of links) to the Haby Hints that concentrate on the information used most in severe storm forecasting. They would not necessarily be in the order that Haby has them (or wrote them).

In fact, this might be a fun group effort. If anyone is game to join in the discussion of what should be understood first, last, and in-between to meet this goal - join us in the Beginner's Forum.