The Role of Elevated Mixed Layers in Severe Weather

[calm_days]

Here is an older topic that is a similar exploration of a less-understood/discussed set of phenomena pertaining to atmospheric composition.

 

http://www.americanwx.com/bb/index.php/topic/38810-the-metallic-vapor-layers

 

It seems that the existence of all of these additional layers of electromagnetic convection and mixing would have functions similar to elevated mixed layers but caused by entirely different particle interactions due to the differences in composition as well as what contributes to their own formation and stability.

 

That is what caused me to remember this topic, you are also asking, why does your phenomena set travel long distances and overall what explains its "behavior"?   

 

I an an amateur but,... I can offer a general statement to add to your exploring.  

 

The phenomena about Eml's that you're noticing, in all its forms, must be interconnected partially or fully with electromagnetic phenomena such as higher atmospheric layers, and also all of the electromagnetic interconnective dynamics observed about lightning (I would like to be able to provide a link so i will look for one again!) between different atmospheric layers and sublayers. 

 

Thanks for your work with this topic!  It's going well, we needed something like this: every day is also the future, a calendar where each block said "future" would be appropriate, maybe it already exists.  So in the future it's important to keep exploring!

 

 

[ThompNickSon]

Hi, calm_days,

 

Thanks for your post and for making me aware of your older thread.    I have read the other thread as best I can and my knee-jerk reaction --- the operative word, here,  might be "jerk" --- is that the order of magnitude of these metal vapours is so much smaller than the order of magnitude of the elements that make up an EML that it is hard to imagine that the vapours could have an effect of sustaining EML's without the causality passing through some factor already within our view -- insolation, glaciation (of clouds) etc.  Because of the thermopause (right?) these layers are substantially isolated from the layers at which "weather" is going on.  But assuming a mechanism to bring these particles past the tropopause (gravity?), might they not figure in determining the conductive properties of the atmosphere, and thus the intensity and frequency of lightning?   Thus, to connect the two threads, we need at least some hypothetical mechanism.  I just don't know enough to know if such a mechanism is even plausible. 

 

As for your being an amateur, there is no more amateurish weather fan than I:  I am, after all, by training an experimental psychologist. However,  I think amateurs have a role to play in all professions.  Like undergraduates, we amateurs can stimulate the experts to state their understandings more clearly and, occasionally, help them discover areas where they have painted over fundamental disagreements.  That being said, they have important day-to-day work to do, and the more we can learn on our own without bothering them, the better. 

 

Take care,

 

Nick

Here is an older topic that is a similar exploration of a less-understood/discussed set of phenomena pertaining to atmospheric composition.

 

http://www.americanwx.com/bb/index.php/topic/38810-the-metallic-vapor-layers

 

It seems that the existence of all of these additional layers of electromagnetic convection and mixing would have functions similar to elevated mixed layers but caused by entirely different particle interactions due to the differences in composition as well as what contributes to their own formation and stability.

 

That is what caused me to remember this topic, you are also asking, why does your phenomena set travel long distances and overall what explains its "behavior"?   

 

I an an amateur but,... I can offer a general statement to add to your exploring.

 

The phenomena about Eml's that you're noticing, in all its forms, must be interconnected partially or fully with electromagnetic phenomena such as higher atmospheric layers, and also all of the electromagnetic interconnective dynamics observed about lightning (I would like to be able to provide a link so i will look for one again!) between different atmospheric layers and sublayers. 

 

Thanks for your work with this topic!  It's going well, we needed something like this: every day is also the future, a calendar where each block said "future" would be appropriate, maybe it already exists.  So in the future it's important to keep exploring!

[ThompNickSon]

Thanks all around to the participants in this thread for improving my understanding of how EML's are sustained.  There are no skyhooks, or membranes.  EML's are sustained simply because they have the good fortune not to be disturbed and that is simply because they never pass over a layer more bouyant than themselves.  The reason they are so bouyand, even tho they are so very dry, is that they are very very warm, and -- here was the great insight for me -- it takes a very small increase in potential temperature to compensate for very very large increases in water vapour content. 

 

There is one other loose end I would like to clear up:  The "book" on EML's is that they arise in the intermountain west.  This seems to me only a part of the story.  If you look at "skewT's" for San Diego, LA, OAK, etc., the air coming in from the Eastern Pacific is extremely dry, just off the "deck".  The pacific ocean off the coast is extremely cold, particularly in the summer.  So the atmosphere coming in from the pacific often consists in a relatively cold moist layer underneath a warmer and extremely dry layer.  As that atmosphere is pushed over the Western Sierra, the lower colder layers are stripped away, and the atmosphere that is DELIVERED to the intermountain west is already very dry and has a very high potential temperature. 

 

Why is all this dry air coming in from an extremely large and wet ocean?   My understanding is as follows: This phenomenon occurs at the outer limits of the first Hadley Cell.  In the inter-tropical convergence zone, warm tropical air rises to great altitudes and is cooled; stripped of its moisture and greatly warmed by condensation, it is pushed poleward and descends to form the return flow at the the surface we call the "trade winds".    As it descends, its potential temperature is realized, and it becomes very warm relative to the cooler, moister ocean boundary layer.   This return flow from the ITCZ is the cause of the ring of deserts around the world that occurs roughly around 20 degrees N and S latitude. 

 

So, I would be tempted to conclude that the origin of EML's is the middle atmosphere of the eastern pacific, which then is further dried and warmed by its passage over the inter-mountain west.

 

What does anybody think of all of that? 

[calm_days]

I think your concept seems accurate, i have seen differences in water vapor imagery over the pacific and atlantic, although here also over land (northern south america).

 

It may have been happening earlier but was noticable to me around october 2012 that the GOES water vapor imagery shows a range that it can't give a gradient (very dry). 

 

 

 

[ThompNickSon]

Thanks, Calm_days.  Great image.  I confess I did not completely understand your second sentence.  Could you say more?

 

The WV image is interesting.  While there is lots of dry air in the northern tropics, there is also substantial chunks of moist air, and I wonder how I am to understand those.  How are they generated.  These aren't the "easterly waves" of which so much is written during hurricane season?  Synoptically speaking, what is an easterly wave?  N
 

[calm_days]

   i have only seen the water vapor gradient show areas where it has not been upgraded to display an image on occasion, so, i'm not sure it has as much to do with your topic after all. 

I can remember it appearing at the time of the storm and hurricane sandy and some of these images are archived. 

 

visual satellite image

 

Here is something different.  The nws sites always describe the ship trails, and, do you know that much of the oscillating convection over some parts of the ocean is formed by microorganisms that can cause precipitation to rise and fall due to subtle biochemical changes?

 

Some aspects of EMLs over the water must be related to the living components of oceanic weather.  Sometimes these precipitating reactions are observed over fields and farms; they are sky microbes and

 there is not always a lot of information about what they do.

[ThompNickSon]

I thought that now the tornado season was starting up again, I would encourage anybody who has been following this thread to post an information relevant to elevated mixed layers. 

 

Here, for instance, is this morning's skew T sounding for Springfield MO, showing, I think, a deep "warm" dry layer overlaying moister "cooler" air.  I tried to paste it in, but the damned thing wouldn't paste.  try http://weather.unisys.com/upper_air/skew/ua_sound.php?type=no&city=ksgf&region=cp&t=-12.

 

Apparently this EML is advecting eastward, because there are severe forecasts for the MI and OH valleys. 

 

 I would be grateful if some of you smart folks would comment on this skewT.  How dangerous does it look.  Is the fact that it is very deep a positive or a negative sign?   I would love to hear some sage commentary on cape and cap, in this case.  What about sheer?  Winds seem brisk at all levels of the atmosphere and windirections remain in the SW quadrant all the way up?  Is this a lot of sheer or a little.   Thanks. N

 

Ps: Does anybody know of a good screen=capture utility that will allow me to save the capture as a picture that can then be put in one of these messages? 

[Ed Lizard]

You should see what kind of 'wasted CAPE' under the cap in CRP and BRO in the late Spring.  4000 plus J/Kg, and it is going nowhere.

 

 

South Texas shouldn't be almost a desert, it has abundant heat and humidity at the surface in the warm months, but rain is infrequent.

 

This is just early April.

[ThompNickSon]

Oh, man! Your post fills me with so many questions!  Do you have a minute?

 

First, where did you get that skewT?  And is there a key that goes with it?  And could you tell me how you got the skewT into the message?   And finally, what did you mean by "wasted" cape?  I sort of see, but would love to have it explained. 

 

We visit Houston all the time ...friends own a stilted house just about where Katrina came across.  Floorboards two feet above the flood line.  It's sort of like Saudi Arabia, right?  A dry place with wet air?

 

In short, please say more, if you have time.

 

N

[Ed Lizard]

SPC website will have skew-Ts for US about 2 hours after the scheduled time, and there is another site I use during tropical season.

 

http://www.spc.noaa.gov/exper/soundings/

 

 

http://weather.uwyo.edu/upperair/sounding.html

[ThompNickSon]

Thanks.  What utility do you use to get the skew T into an amerWX posting?  n

[Ed Lizard]

Thanks.  What utility do you use to get the skew T into an amerWX posting?  n

 People more practiced then myself, amateur and degreed mets, use actual and forecast skew-Ts to estimate where/when severe weather may happen.

 

NIU web site has a forecast skew-T generator, other university sites do as well.  http://www.twisterdata.com/ is a good site for forecast maps, which can then suggest prime locations for looking at forecast skew-Ts.

 

It takes a while for an amateur to get good at it, I am decent but there are amateur severe weather enthusiasts that post in the Central/Wstern subforum who are much better than I am.  ( http://www.americanwx.com/bb/index.php/forum/14-centralwestern-states/ )  Checking SPC daily severe progs can suggest other sub-forums where threads might have been started.

 

Read, learn, ask questions.  Can also self educate, to a degree, on the internet.  http://www.bing.com/search?q=skew-t+tutorial&qs=AS&sk=AS2&pq=skew-t&sc=8-6&sp=3&FORM=QBLH&cvid=810f458ff2fe407896cdfb1b28d7a471

 

And there is an 'Ask a Met' forum as well.  http://www.americanwx.com/bb/index.php/forum/30-meteorology-101/

[Ensō]

Re: skew-Ts, MetEd has an excellent module for learning the basics. They have a number of great severe weather education modules, actually. Here's the skew-T primer.

 

http://www.meted.ucar.edu/mesoprim/skewt/

 

As for how to post a skew-T on the forum, the simplest way is to right click the image, go to "copy image URL" (or similar wording, depending on what browser you use), and then when you make a post here just click on the picture icon right underneath the smiley face and to the left of the code button, hit ctrl+v, and click okay.

[ThompNickSon]

Dear Enso, 

 

Thanks for for educational materials.  I have actually been through that site a couple or three times, but there is only so much I can learn with out TALKING to somebody about it. Apologies if I am a bore. Any help you could give me is appreciated.

 

Thanks, also, for the tips on how to post a SKEWT.  I followed them and they WORKED!  See below,

 

KBNA is nashville, north of where there is a slight chance of severe weather today.  The soundings in the actual forecast area don't seem very interesting, so I sent this one along. It shows (does it not?) three successive layers of dry, and [potentially] warm air, and some pretty spectacular sheer, right?  140 mph jet?  What kind of weather would you expect on a day like this?  You have [potentially] warmer and warmer air with increasing altitude (and so stable), but you also have dry air over moist (and so unstable?). How to balance those two factors always puzzles me. 

 

N

 

 

 

[ThompNickSon]

The only place where tornadoes might happen today is apparently South Florida (!).   Note two overlying layers of dry air with the characteristic triangular shape as moisture collects at the top of the dry layer.  This chart is way too complicated for me.  Curious to know what others see in it. 

,,

Here is the skew T.

N

[Ed Lizard]

The only place where tornadoes might happen today is apparently South Florida (!).   Note two overlying layers of dry air with the characteristic triangular shape as moisture collects at the top of the dry layer.  This chart is way too complicated for me.  Curious to know what others see in it. 

,,

Here is the skew T.

N

 

 

Not enough low level winds, IMHO, for a significant tornado threat.  Now, HOU area, late in the season when winds are generally light in the sounding, and there is a somewhat more 'tropical' looking sounding, that is sometimes the time of tropical funnels, which will rarely touch down, usually as EF-0 or EF-1 tornadoes.

 

I'm ***guessing*** boundary interactions is what provides the spin for tropical funnels.  Can get them in sea breeze storms,

[ThompNickSon]

So the dry layers in this sounding are not part of what is causing NOAA to put up watches?  I have to admit, surface dewpoints are not very impressive. 

 

What you called a "tropical funnel" I would probably call a waterspout, right?   Son in law in Seabrook had one of those come off Galveston Bay and plow right over his house, once.  Not much happened. He was so busy taking pictures he never stopped to think what might have happened.

[Ed Lizard]

So the dry layers in this sounding are not part of what is causing NOAA to put up watches?  I have to admit, surface dewpoints are not very impressive. 

 

What you called a "tropical funnel" I would probably call a waterspout, right?   Son in law in Seabrook had one of those come off Galveston Bay and plow right over his house, once.  Not much happened. He was so busy taking pictures he never stopped to think what might have happened.

 

 

Not following it.  But maybe the 12Z sounding and/or forecast soundings show an increase in wind shear.

[weatherwiz]

Don't forget, forecast soundings are just a piece of the puzzle!  Forecast soundings are fantastic b/c they show you a profile of the atmosphere from the surface up through pretty much to the tropopause.  Great way to view wind shear at the time of the launch and numerous other variables such as instability, thermal profiles, dewpoint profiles, moist layers, dry layers, lapse rates, etc.  Always make sure you're looking at other parameters and model graphics as well to determine strength and degree of lift, your forcing mechanisms, etc.  

 

On the skew-t you posted from MFL as Ed Lizard stated, you don't really have string low level winds in place, however, there is some decent directional shear but the degree of helicity is lessened due to the weak wind fields.  Speed shear is also lacking as well...note that as you increase with height winds aren't really strengthening, although between maybe 650mb on up you start getting stronger speed shear.  This all leads to that messy looking hodograph you see on the top right.  

 

Also note that while you have a very steep lapse rate environment between about 900 and 600mb you have very poor lapse rates between 850-500mb .  There is really no EML present here IMO.  Notice as well the surface cape of 2074 then forecast surface cape of only 430...now perhaps a front is moving through there at some point (I don't know the synoptic setup) but one guess I would have is with the lack of EML present and such dry air aloft, that dry air will mix down to the surface, lower dews and the result will be less Cape.  

 

If your question is threat for tornadoes, I wouldn't rule it out based on that sounding...definitely a possibility, not great but given the location of the sounding, sea-breeze enhancement could enhance the low-level flow a bit and lead to localized higher helicity values.   

[ThompNickSon]

Thanks WxWiz,

 

I found your discussion of the sounding very helpful. 

 

I am curious why you don't see an EML there,  I thought that the two vaguely triangular shapes, formed by the temp and dewpoint lines jutting to the right and left (respectively) and then converging higher up each CONSTITUTED an EML.  So, where you saw none, I saw 2! 

 

Can you say more?

 

Oh, by the way, you are correct about the front. 

 

N

[It's Always Sunny]

Thanks WxWiz,

 

I found your discussion of the sounding very helpful. 

 

I am curious why you don't see an EML there,  I thought that the two vaguely triangular shapes, formed by the temp and dewpoint lines jutting to the right and left (respectively) and then converging higher up each CONSTITUTED an EML.  So, where you saw none, I saw 2! 

 

Can you say more?

 

Oh, by the way, you are correct about the front. 

 

N

You can make an argument that those are EML's but like Wiz said the lapse rates really aren't that great. Anything 6.5C/km and greater then we can start talking.

[ThompNickSon]

Thank You.  I have to pay closer attention to the negative tilt of that right hand line.  N

[LocoAko]

Thank You.  I have to pay closer attention to the negative tilt of that right hand line.  N

 

Yep. Good discussion in this thread. Not sure if you're aware of the SPC mesoanalysis, but the Mid-Level Lapse Rates plot (shown below) is good for tracking areas of very steep lapse rates (often associated with EMLs) in real-time. Of course just the presence of steep ML lapse rates isn't enough to spawn convection, but given other ingredients in place and a dearth of soundings, this can serve as a decent approximation to where EMLS may lie. 

 

[weatherwiz]

You can make an argument that those are EML's but like Wiz said the lapse rates really aren't that great. Anything 6.5C/km and greater then we can start talking.

 

Would be great side debating right there...and extremely educational!  I remember though I think it was this past summer, may have been the summer prior but we had a setup up here where it looked like a very shallow EML...too make a long story short Arnold14 chimed in and stated while it appeared to look like an EML true EML's are located up usually in the 800-550mb range or so.  

 

Thanks WxWiz,

 

I found your discussion of the sounding very helpful. 

 

I am curious why you don't see an EML there,  I thought that the two vaguely triangular shapes, formed by the temp and dewpoint lines jutting to the right and left (respectively) and then converging higher up each CONSTITUTED an EML.  So, where you saw none, I saw 2! 

 

Can you say more?

 

Oh, by the way, you are correct about the front. 

 

N

 

The graphic LocoAko posted is an excellent way to take a look at where an EML is located.  If you're unsure of where to find that graphic just go to the spc homepage, look for mesoanalysis, click on a sector then under thermodynamics look for 700-500mb lapse rates. 

 

Going back to the sounding you posted, if you look at the 850-500mb lapse rates and the 700-500mb lapse rates, they are beyond poor, 5.5 C/KM and 4.2 C/KM, respectfully.  That is pretty tropical like.  Really for EML's you want to at least be looking at 7 C/KM lapse rates but very true EML's usually have lapse rates at least 8 C/KM or greater and in the 700-500mb levels.  

 

In that sounding, you have a pretty steep low level lapse rates environment but this resides below the areas where EML's are located and where EML's are defined.  

 

Just take a look at examples from this page...scroll down about 3/4 of the way down and there are a ton of examples...notice in all of them the EML is located above 850mb.  

[ThompNickSon]

thanks, everybody, for great posts.  I will have a look at those resources.

 

WXWIZ, I had one question about yours.  You wrote:

 

Just take a look at examples from this page...scroll down about 3/4 of the way down and there are a ton of examples...notice in all of them the EML is located above 850mb.

 

Which page are you speaking of?  I didn't see any links in your message.  Were you referring to the SPC page? 

 

Thanks, again

 

N

[LocoAko]

thanks, everybody, for great posts.  I will have a look at those resources.

 

WXWIZ, I had one question about yours.  You wrote:

 

Just take a look at examples from this page...scroll down about 3/4 of the way down and there are a ton of examples...notice in all of them the EML is located above 850mb.

 

Which page are you speaking of?  I didn't see any links in your message.  Were you referring to the SPC page? 

 

Thanks, again

 

N

 

http://www.spc.noaa.gov/exper/mesoanalysis/

 

From there, you can pick a sector, and the mid-level lapse rate graphic is found under the Thermodynamics tab. 

[It's Always Sunny]

Would be great side debating right there...and extremely educational!  I remember though I think it was this past summer, may have been the summer prior but we had a setup up here where it looked like a very shallow EML...too make a long story short Arnold14 chimed in and stated while it appeared to look like an EML true EML's are located up usually in the 800-550mb range or so.  

 

Yeah he's right. 800 mb isn't even that high up ( a little over a mile in most situations) Anything below that is just a mixed layer to me.

[ThompNickSon]

Thankyou all for putting me on to the SPL's experimental page.  I am like a kid in a candy store!  With this tool, it will be possible to track EML's atround the country and perhaps to better understand why they remain aloft.  (I know that question got answered, but it is still an intuitive snag for me whenever I see moist air UNDER dry air. 

 

One question.  Why are lower level lapse rates less important?  I assume it's because you need to have room to put some moist air UNDER the dry level before it's dangerous.  Also, more room for shear? 

 

Thanks again, everybody!   What a group!

 

N

[weatherwiz]

thanks, everybody, for great posts.  I will have a look at those resources.

 

WXWIZ, I had one question about yours.  You wrote:

 

Just take a look at examples from this page...scroll down about 3/4 of the way down and there are a ton of examples...notice in all of them the EML is located above 850mb.

 

Which page are you speaking of?  I didn't see any links in your message.  Were you referring to the SPC page? 

 

Thanks, again

 

N

 

sorry...

 

http://bangladeshtornadoes.org/EML/emlpage.html

 

scroll 3/4 of the way down and there numerous links which provide examples

[weatherwiz]

Thankyou all for putting me on to the SPL's experimental page.  I am like a kid in a candy store!  With this tool, it will be possible to track EML's atround the country and perhaps to better understand why they remain aloft.  (I know that question got answered, but it is still an intuitive snag for me whenever I see moist air UNDER dry air. 

 

One question.  Why are lower level lapse rates less important?  I assume it's because you need to have room to put some moist air UNDER the dry level before it's dangerous.  Also, more room for shear? 

 

Thanks again, everybody!   What a group!

 

N

 

Well low-level lapse rates are very important, it's just they have little do do with EML's.  

 

I have class in 10 min so don't have time to explain further but perhaps someone else can