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Tutorial Snow Forecasting & Weather Knowledge Base

Discussion in 'Alpine & Snow' started by POW_hungry, Aug 17, 2020.

  1. POW_hungry

    POW_hungry Old n' Crusty Moderator Ski Pass: Gold

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    We can go pretty DEEP in these Snow Weather forums, so here's place to keep all the fiddly information in one spot.

    Don't know what a particular meteo topic means? Confused about a Global Model Plot? Don't know the name of that cloud?
    Then post a brief intro into what you do/don't know or understand about a particular weather related topic (or resource) with a valid question about what you want to know and your answer shall be answered and/or debated to help all & sundry understand.

    Some basic guidelines & etiquette:
    • This thread is all inclusive of skill/knowledge; from a chief meteorologist to an absolute noob. It doesn't matter
      • Skill level is not a hierarchy in here
    • Hot heads can leave the ego in the Bear Pit. Trolls will be handed a 'straight to jail' card and dealt with accordingly
    • All topics are to be discussed constructively
    • It helps if you're explaining something to back it up with some resources/links
    If you've never stepped foot into the weather forum it's good to know some basic weather (WX) terms & phases. BoM has a good list published HERE.
     
    Snowy Joey, Ijay, Big_Red_60 and 5 others like this.
  2. Nidecker

    Nidecker One of Us Ski Pass: Gold

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    Not that it needs to be, but I find if I leave the comment to the skilled crew in the predictions, but as a "lesser individual" add some input into the obs threads, its a good way to go :) YMMV
     
    Richard likes this.
  3. Jellybeans

    Jellybeans not woke enough Ski Pass: Gold

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    Wondering if this little basic tutorial I made with skiers in mind a few years back would help. It was made for an American audience, but I have adapted it to make it more relevant to Australia.

     
    Noah, Big_Red_60, JindySuz and 4 others like this.
  4. teleroo

    teleroo Ignored Member Ski Pass: Gold

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    Just sharing my own internet tootling on the Madden Julien Oscillation. Here is a MJO plot from:
    https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ecmf.shtml

    [​IMG]

    You all can read up on the general behaviour of the MJO on the internet - BOM has a good youtube vid. What I was lacking was knowledge on how to interpret the graph above. So here goes. From the title it is a forecast of MJO values (using the ECMWF model) for 23 August to 06 Sept 2020. These are the dots within the thick green line (each day is a dot). Red line is last 40 days. Now, the MJO is basically an eastwards moving zone of tropical convection and moisture generation that circulates around the equator. The entire loop around the equator has been divided into eight "phases" (sections of longitude). Australia lies in the middle of phases 4 and 5. So on the above graph, the MJO was both strong and positioned roughly north of Australia between 5th and 8th August. The convection to Australia's north provides a good source of moisture and this fed into the Hand of Faith system discussed here:
    https://www.ski.com.au/xf/threads/august-2-8th-the-hand-of-faith.88101/

    The MJO then weakened and tracked eastwards across the Pacific Ocean (phases 6 and 7) and currently is over Africa. The strength of the MJO is indicated by how far each day (dot) is away from the inner black ring - the further out the stronger the MJO. So the current MJO forecast has it strengthening a little further over next four days whilst in phase 1, before progressively moving east and being over Australia again around 06 Sept. But next time it returns over Oz, it is currently forecast to be within the inner circle, so therefore not very strong.

    Legend from website above: "Phase diagram showing the evolution of the last 40 days of observations along with the 15 day ensemble ECMWF forecast. The yellow lines are the 51 ensemble members and the green line is the ensemble mean (thick-week 1, thin-week 2). The dark gray shading depicts 50% of the members fall in this area and the light gray shading indicates 90% of the members. "
     

    Attached Files:

    Jellybeans, SnowBound, Noah and 3 others like this.
  5. Noah

    Noah One of Us Ski Pass: Silver

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    Thank you @Jellybeans, can't believe how readable they all are now, I'll be coming back to your explanations a lot. And @teleroo I was just going to ask that very question about the MJO plot and you've explained it beautifully.

    So all I have now is for someone to please explain the '500hPa Longwave'. Prior tutorial threads had links to a video that is no longer up.

    Thank you.
     
    teleroo and Jellybeans like this.
  6. POW_hungry

    POW_hungry Old n' Crusty Moderator Ski Pass: Gold

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    NWS does a simplistic rundown on NH Long Wave Pattern, same principles apply to the SH pattern.
    https://www.weather.gov/jetstream/longshort
     
    Big_Red_60 and Noah like this.
  7. Swiss

    Swiss One of Us Ski Pass: Gold

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    I'd be keen to see a post explaining all the different types of snow (falling and on the ground) described in some of these threads.

    We all know what things like sleet and powder are, but a little glossary of terms like graupel, sastrugi, sago, spring corn and the rest would be great.
     
    Jellybeans and POW_hungry like this.
  8. Big_Red_60

    Big_Red_60 One of Us

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    POW_hungry likes this.
  9. POW_hungry

    POW_hungry Old n' Crusty Moderator Ski Pass: Gold

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    I'll get to this in the coming weeks. Good topic.
     
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  10. Jellybeans

    Jellybeans not woke enough Ski Pass: Gold

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    Would this work, someone wrote this on Wikiski (which is technically part of this site) some time ago?
    http://www.wikiski.com/wiki/index.php/Category:About_Snow
     
    POW_hungry, Swiss and Noah like this.
  11. Jellybeans

    Jellybeans not woke enough Ski Pass: Gold

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    POW_hungry likes this.