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Author Topic: Winter WX Basics  (Read 34550 times)

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Offline Chelsea in Tn

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Re: Winter WX Basics
« Reply #15 on: January 17, 2011, 06:45:13 PM »
Thank you so much for your time and effort to put this together. I do not have time to read all of it now... but I definitely will be reading it!
Chelsea

That’s what troubles me. This notion that we have to take sides in this country now, you’re either with us or against us, Republican or Democrat, red state or blue state. No one looks at an issue and struggles over the right position to take anymore. And yet, our ability to reason is what makes us human. Lately, we seem so willing to forfeit that gift of reason in exchange for the good feeling of belonging to a group. We all just take the position of our team.”
-Alan Shore (Boston le

Offline SKEW-TIM

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Re: Winter WX Basics
« Reply #16 on: February 02, 2011, 08:42:28 AM »
Can someone please explain - Upper Level Lows are vs. Surface Level Lows? I know what LOW Pressures are, but, I am not that familiar with ULLs or a surface low....   
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Offline justinmundie

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Re: Winter WX Basics
« Reply #17 on: February 02, 2011, 08:48:38 AM »
Can someone please explain - Upper Level Lows are vs. Surface Level Lows? I know what LOW Pressures are, but, I am not that familiar with ULLs or a surface low....   

It's basically a difference in where the low is in the atmosphere. Surface lows are at the surface. Upper level lows are at 500mb
Snow lover who moved to a place where it never snows.

Offline SKEW-TIM

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Re: Winter WX Basics
« Reply #18 on: February 02, 2011, 08:54:49 AM »
Is one stronger than the other? Or is it simple just a case of where the area of circulation is?

For example:

SURFACE LOW- Circulation and weather system is at the ground

ULL- Circulation and weather system is above 500mb- Which means the effects of the system can be felt higher up?
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Offline justinmundie

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Re: Winter WX Basics
« Reply #19 on: February 02, 2011, 09:08:31 AM »
Is one stronger than the other? Or is it simple just a case of where the area of circulation is?

For example:

SURFACE LOW- Circulation and weather system is at the ground

ULL- Circulation and weather system is above 500mb- Which means the effects of the system can be felt higher up?


No each system has different dynamics. A ull can spin up a surface low and they work in tandem.  But they bot h translate to weather at the surface
Snow lover who moved to a place where it never snows.

Offline SKEW-TIM

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Re: Winter WX Basics
« Reply #20 on: February 02, 2011, 09:21:17 AM »
I see, So a ULL can create a Surface Low- Does that intensify the Low Pressure system? or is that what they "closing off" ? 
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Offline Stovepipe

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Re: Winter WX Basics
« Reply #21 on: February 02, 2011, 11:26:42 AM »
Seems like a good place to ask my question.  Why is it, when looking at the upper air maps, the energies (vorts, eddys, s/w's etc) are generally 100 to 200 miles behind where the precip is breaking out on the surface?  What causes this apparent lag?

I'd love to get some pointers on reading the H5 maps in general.  I mean I can get the gist of the flow of the troughs but it isn't clear to me how this corresponds to what we see on the surface maps.  I do notice that the front side of these upper level energies often lines up perfectly with the 540 thickness line shown on the surface.

Any insight on this would be appreciated.

Offline Thundersnow

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Re: Winter WX Basics
« Reply #22 on: February 02, 2011, 11:32:31 AM »
I believe that's how systems typically work... the precip will tend to be out ahead of the center of the low, since that's where the inflow of moisture is.

Offline Nashville_Wx

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Re: Winter WX Basics
« Reply #23 on: September 13, 2011, 08:48:35 PM »
I believe that's how systems typically work... the precip will tend to be out ahead of the center of the low, since that's where the inflow of moisture is.

Precipitation is most likely to right of shortwave axis/500mb trough axis.


Offline Cyclonicjunkie

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Re: Winter WX Basics
« Reply #24 on: September 13, 2011, 09:40:40 PM »
Seems like a good place to ask my question.  Why is it, when looking at the upper air maps, the energies (vorts, eddys, s/w's etc) are generally 100 to 200 miles behind where the precip is breaking out on the surface?  What causes this apparent lag?

Hey Stove, I know this is a old question but I didnt see it until Nashville wx brought this thread out of the graveyard ;D


Some extratropical surface lows become so strong that they bend towards the direction they are headed. That alone is enough to displace the upper level energy/ULL hundreds of miles away to the west, SW, or NW. But usually the reason you see this... is that troffs and shortwave troffs associated with extratropical surface lows bends towards the cooler air which pushes the ULL's/ upper level vorticies/energies that accompany the surface low farther away to the west, SW, or NW from the actual low level stormcenter that u see on radar.

Now when the upper low and surface low become stacked it is due to a strongly amplified troff becoming closed off and the rest of the upper level jet is free to race off straight ahead. Then the surface low sorta loses its baroclinicity and steering mechanism to some degree allowing the ULL to fill in and become vertically stacked above the surface low..... much like a tropical systems evolution. ::rain::

But when this happens it usually becomes cut off from the jet stream ( Hence the name cutoff low) and there isnt much left to steer it and it sorta just sits there and weakens as it dumps its energy in the form of precip whether that be rain (You've ever heard the terminology 'Rain itself out") or it could be snow depending on the temps of the airmass it occupies. ::snowman::

Or some other synoptic system will grab hold of it, and steer it away to possibly restrengthen. But once an extratropical system loses alot of its baroclinicity it will lose it's source for attaining energy and if it dont regain some baroclinicity soon it won't be able to deepen or intensify.
 

Thats how I understand it anyways, if you have any more specific questions on upper air meteorology, just ask me and I will answer it if I can. :)


 

« Last Edit: September 13, 2011, 11:52:18 PM by Cyclonicjunkie »

Offline Adam

Re: Winter WX Basics
« Reply #25 on: September 13, 2011, 09:45:37 PM »
Does anyone know if there is any sort of skill to pointing out where a heavy band of snow may form in a snow storm. Lately they have really been South of I-40 I was just wondering why.
AND A LOT CAN CHANGE BETWEEN NOW AND THEN.

Offline Cyclonicjunkie

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Re: Winter WX Basics
« Reply #26 on: September 13, 2011, 10:08:52 PM »
Does anyone know if there is any sort of skill to pointing out where a heavy band of snow may form in a snow storm. Lately they have really been South of I-40 I was just wondering why.

Usually you will get the heaviest snow right on the border of the cold and warm sectors of a LPS. This is where there is ALOT of moisture available because of the warmer air and its just barely cold enough to snow so you get the best of both worlds....Warm moist air mixed with temps just barely cold enough to turn the moisture into snow. Its usually big wet silver dollar flakes in this hybrid zone.

Offline Nashville_Wx

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Re: Winter WX Basics
« Reply #27 on: September 14, 2011, 12:18:01 AM »
Does anyone know if there is any sort of skill to pointing out where a heavy band of snow may form in a snow storm. Lately they have really been South of I-40 I was just wondering why.

The storm took a track that was favorable for that area. Different type of systems have different zones that favor heavy snow. The area where vertical lift is the strongest, strong omega zone values... Heavy snow can have many different moisture contents so the total QPF could be different. Hopefully we all can watch things pan out this year. I am ready for 7-8" + Imby...


Offline Cyclonicjunkie

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Re: Winter WX Basics
« Reply #28 on: September 14, 2011, 01:28:11 AM »
Different type of systems have different zones that favor heavy snow.

You only have two diferent type of extratropical systems in general that produce snow here. You have your normal Mid lattitude extratropical cyclone (Miller a's, b's  Southern sliders, Alberta clippers, Manitoba Maulers, Apps Runners, and Lakes cutters) are all extratropical mid lattitude cyclones that only produce snow  in the cold sector of the LPS here in the SE.

Then you have a upper/mid level LPS (AKA cold core low, AKA bowling ball) which produces its on cold air dynamically and at the center of the ULL/MLL., you will find most, if not all of the snow in these at the very center of the low. 

They are really unpredictable and are usually diurnally driven due to the sun warming the ground and destabilizing the atmosphere and that causes upward VERT motion which usually only creates snow during the day.

All of this is why you usually dont know where the snow will fall with these types of LPS's that are aloft.
« Last Edit: September 14, 2011, 01:35:56 AM by Cyclonicjunkie »

Offline Thundersnow

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Winter WX Basics
« Reply #29 on: September 14, 2011, 07:47:48 AM »
(Miller a's, b's  Southern sliders, Alberta clippers, Manitoba Maulers, Apps Runners, and Lakes cutters)

And, don't forget about Saskatchewan Screamers. ;)

 

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