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  • 17-11-2011 12:38pm
    #1
    Lustrum
    Registered Users Posts: 741 ✭✭✭


    In the attached surface weather chart there is a dashed line just to the east of the warm front that is over Russia with the number 528 connected to it. There are a couple of similar lines on the chart numbered 546 and 564. Has anyone any idea what they are?

    20111118PPVG89V1200_large_0.pdf


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    #2
    Lustrum
    Registered Users Posts: 741 ✭✭✭Lustrum


    Sorry that image doesn't seem to have worked, here's the link

    http://www.avbrief.co.uk/chartsfree/meto/20111118PPVG89V1200_large_0.pdf


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    #3
    pauldry
    Registered Users Posts: 6,877 ✭✭✭pauldry


    No ideas mate.

    Jetstream tracker ? The one near Ireland seems to correspond with the Jetstream around our parts.


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    #4
    Su Campu
    Closed Accounts Posts: 4,279 ✭✭✭Su Campu


    They're the 500-1000 hPa thickness lines, showing the distance between the two pressure levels, in decameters (dm). 528 dm = 5280 m. The smaller the number the colder the airmass. If we get around 528 or lower then we can get snow.


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    #5
    Lustrum
    Registered Users Posts: 741 ✭✭✭Lustrum


    Su Campu wrote: »
    They're the 500-1000 hPa thickness lines, showing the distance between the two pressure levels, in decameters (dm). 528 dm = 5280 m. The smaller the number the colder the airmass. If we get around 528 or lower then we can get snow.


    Thanks for that Su Campu. Now just to make sure I understand this properly, is it using 1000hpa as the reference pressure and it is 5280m vertically up to the 500hpa level?

    Using an ISA atmosphere this distance should only be 4000m which would suggest that the airmass is quite a bit warmer than standard. Or is this completely unconnected?

    Also do you have a name for which type of isopleth it might be? At the moment the best I can do is a thickness line


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    #6
    Su Campu
    Closed Accounts Posts: 4,279 ✭✭✭Su Campu


    Lustrum wrote: »
    Thanks for that Su Campu. Now just to make sure I understand this properly, is it using 1000hpa as the reference pressure and it is 5280m vertically up to the 500hpa level?

    Using an ISA atmosphere this distance should only be 4000m which would suggest that the airmass is quite a bit warmer than standard. Or is this completely unconnected?

    Also do you have a name for which type of isopleth it might be? At the moment the best I can do is a thickness line

    Correct, it's the 500 hPa height minus the 1000 hPa height.

    The standard thickness is actually 552 dm (5.52 km), varying from around 470 to 600. Not sure where you got 400.

    I can't for the life of me remember the name of the isopleth but I'll have a look in my book later!

    EDIT: The AMS Glossary calls it a relative isohypse (isohypse is a line joining points of equal geopotential).


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    #7
    Lustrum
    Registered Users Posts: 741 ✭✭✭Lustrum


    Thanks for that Su Campu, much obliged. And I've just copped on to the bu-bu I made to get 4000m (taking a 1 hpa decrease every 8m, but of course as you get higher that distance gets larger whereas I just multiplied the 500hpa difference by 8)

    Thanks again


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    #8
    Su Campu
    Closed Accounts Posts: 4,279 ✭✭✭Su Campu


    Had a look at the text book and the only name I can find for the thickness isolpleth is either relative isohypse or simply thickness contour.

    Incidentally, there's a list of 23 other isopleths and their definitions.....see how many you can get! :)

    Isallobabar
    Isallohypse
    Isallotherm
    Isanabat
    Isanomal
    Isentrope
    Isobar
    Isobath
    Isobathytherm
    Isoceraunic
    Isochrone
    Isodop
    Isodrosotherm
    Isogon
    Isohel
    Isohume
    Isohyet
    Isohypse
    Isoneph
    Isopycnic
    Isoshear
    Isotach
    Isotherm


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    #9
    thetonynator
    Closed Accounts Posts: 5,234 ✭✭✭thetonynator


    Su Campu wrote: »
    Isopycnic

    I like that one!


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    #10
    Lustrum
    Registered Users Posts: 741 ✭✭✭Lustrum


    Without google!
    Su Campu wrote: »
    Had a look at the text book and the only name I can find for the thickness isolpleth is either relative isohypse or simply thickness contour.

    Incidentally, there's a list of 23 other isopleths and their definitions.....see how many you can get! :)

    Isallobabar
    Isallohypse
    Isallotherm
    Isanabat
    Isanomal
    Isentrope
    Isobar - Pressure
    Isobath
    Isobathytherm
    Isoceraunic
    Isochrone
    Isodop
    Isodrosotherm
    Isogon - Variation
    Isohel
    Isohume - humidity? (or an obvious mistake!)
    Isohyet
    Isohypse - height
    Isoneph
    Isopycnic
    Isoshear change of wind speed/direction?
    Isotach - windspeed
    Isotherm - temperature

    I'll have to ask my friend the internet for the rest. Great info though thanks


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    #11
    derekon
    Registered Users Posts: 836 ✭✭✭derekon


    Lustrum wrote: »
    In the attached surface weather chart there is a dashed line just to the east of the warm front that is over Russia with the number 528 connected to it. There are a couple of similar lines on the chart numbered 546 and 564. Has anyone any idea what they are?

    20111118PPVG89V1200_large_0.pdf

    Hi Lustrum, to illustrate Su Campu's points , take a look at the temperature charts for this time last year for Monday 20th December 2010.

    There was very heavy snowfall that day on the East Coast of Ireland - you will also note from the map that the "528" line was well south of the island, thus ensuring that any precipitation that fell that day fell in the form of snow. And Dublin got HAMMERED! :D:D:D


    http://www.meteociel.fr/modeles/archives/archives.php?day=20&month=12&hour=12&year=2010&map=3&mode=2


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