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'a Simple Guide To Understanding Skew-T Diagrams


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Posted
  • Location: Hillmorton,Rugby,Warwickshire.ASL 97m
  • Location: Hillmorton,Rugby,Warwickshire.ASL 97m

Thanks JohnIi shall have lots of questions to ask,Dave i hope weather plays ball next week and who knows we may get some excitement although i did get to see some nice cloud formations today and thought i saw mamma clouds at work but maybe not,it did look like colder pockets of air in the cloud to make them droopy looking.I have a picture in my album online.Dave with reference to your previos post,I see the areas of CIN,CAPE and LFC but who do you get the readings and Know the area it covers also what pressure do you get T and TDP and other readings.

Edited by Anvil Crawler
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Posted
  • Location: Exeter, Devon, England
  • Location: Exeter, Devon, England

This skew-T for today at Nottingham (12Z): http://weather.uwyo.edu/cgi-bin/sounding?r...1012&STNM=03354

has a raw data output with it: http://weather.uwyo.edu/cgi-bin/sounding?r...1012&STNM=03354

This lists Pressure, height (meters), temp, dew point, relative humidity, Mixing ratio, Wind direction, wind speed.

nott0yt.jpg

If you scroll to the bottom of that page it has all the useful parameters:

Convective Available Potential Energy: 0.35

Convective Inhibition: -28.07

Equilibrum Level: 806.50

Level of Free Convection: 831.78

Pres [hPa] of the Lifted Condensation Level: 916.94

Precipitable water [mm] for entire sounding: 8.75

So you can see there is little CAPE, quite a bit of CIN limiting convection, the EL is very low (806hPa) so you wouldn't expect cloud tops to be high, and the LCL is 916hPa (about 900m) so that's where you'd expect cloud base to form, probably only flat cumulus spreading into stratocumulus because of the low Equilibrium level (Inversion) present.

You can also see that 8.75mm of rain would be produced if deep convection occured.

Check out this site for soundings all over the world with an archive back to 1973!! :nonono:

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

And this is a random sketch to show what the Sc/Cu clouds formed would look like in height. :)

nott26vq.jpg

Edited by Dave J
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Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

hi Anvil

If I can remember, I will do an example, using a skew-t for 12z tomorrow with a local temp and dewpoint and show you how simple it is to do it yourself.

If I have not posted by about 1500, remind me mate!

regards

John

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Posted
  • Location: Hillmorton,Rugby,Warwickshire.ASL 97m
  • Location: Hillmorton,Rugby,Warwickshire.ASL 97m

Thanks Dave :wallbash: Nice image of sc/cu,This is the understanding i have to get round.I see the data and pecip possibility if deep convection had occured.With Regards To CIN ( Convective Inhibition) you say the figure of -28.7 is high limiting convection so if it was +28.7 that would be good.I understand if we have CAPE of 1000 j/kg and say LI of -6 this would be good but not always the case.Do you alway's use RAW data to get the info required as you have shown and are the readings always taken from 850 to 1012 hpa even so that alot more readings are taken.I do see the wind speed and direction but we come to that later as this ties in with vertical and horizontal shear.

Thanks John if would be good if you could post one.

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  • 5 months later...
Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

not exactly what you asked for but this site may help you

http://weather.unisys.com/upper_air/skew/details.html

John

I honestly think if you read slowly and carefully through my posts/teach-in, you should understand most of it. By all means ask questions or send me a pm and I'll do my best to answer your queries.

regards

John

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Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

sorry no idea, in the first two or three diagrams I build up what one looks like. Is that not any good?

John

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  • 1 year later...
Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

to anyone wanting to use this to learn about skew-t diagrams I apologise for the number of charts that will not open. Some of them I have kept on my pc, some I have not.

As soon as I can I will try and replace the black ones.

In the meantime anyone using this tutorial if that or anything else causes you to get 'stuck' understanding them, then please either put a post up here or pm me and I'll try and help.

I've just gone through this and there are a fair number of diagrams I may have to re do to replace the ones that will not open, and also to put in some relevant 'actual' skew-t examples, so bear with me as it will take some time to get it done.

Edited by johnholmes
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  • 1 year later...
Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

hi anyone

I'm just trying to sort what is not available after NorthNorfolk Wx pointed out some diagrams would not open.

As far as I can make out the following seem not to open

diagram 2

diagram 5

06z for London Friday 6 May 2005

and this

the chart is actually the 06Z not 12Z, and is shown below

If someone could check they get the same problem and post their comment back in here it would be a great help in knowing what I have to rry and correct??

many thanks if some will do this

John

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Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

hi again

I've had one reply which seems to confirm what I posted above-the poster also commented that it was impossible to reply on this thread?

can anyone else who has tried and had that problem please pm me

many thanks

John

ps

the post in 2008 was before I had done the necessary amendments to problems which had occurred then-so until this I had assumed all was okay?

j

Edited by johnholmes
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Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks
hi again

I've had one reply which seems to confirm what I posted above-the poster also commented that it was impossible to reply on this thread?

can anyone else who has tried and had that problem please pm me

many thanks

John

ps

the post in 2008 was before I had done the necessary amendments to problems which had occurred then-so until this I had assumed all was okay?

j

tks for the pm's folks

I'll try and sort the problems as indicated above some time tomorrow

John

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Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks
tks for the pm's folks

I'll try and sort the problems as indicated above some time tomorrow

John

having problems its plain to see

no idea how to delete the charts at the bottom so I'll have to pm Paul to ask how to do it.

John

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Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

well in spite of me trying and Paul giving advice its not working-my apologies to everyone who is trying to use them; North Norfolk Wx I am still trying to get the damn thing to work for all links.

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  • 6 months later...
Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

As I'm getting a number of pm's regarding the skew-t diagrams, thanks to the possible snow this week (its Mon 8 Feb 2010),

I've checked what seems not to be working in the diagrams and it seems to be Diagram 5 and Diagram 8-for me the rest work.

I'll see if I can correct them but it may not be possible.

What I may have to do is a full rewrite which would give me the chance to try and produce rather clearer or shall I say more professional looking diagrams. However it will take a lot of time and effort so please be patient, I'm talking many weeks!

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  • 1 year later...
Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

as far as I can see all the charts open; I will look for an example of convection to illustrate again how to use a skew-t.

If anyone is still having a problem opening any of the diagrams please let me know.

At some time, I cannot suggest when, I will try and produce some rather more professional diagrams. I may need to beg or borrow off other folk so it may take a while. If that does not work then it will take even longer to try and produce more professional looking charts myself!

Edited by johnholmes
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