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Dr. Astro

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    Model Output Discussion - The Start Of Winter

    in Forecast Model Discussion

    Posted · Edited by Dr. Astro

    Seeing as we appear to be in an MJO led base state at present, should modelling firm up on us progressing into phase 6/7 then some 'stellar' charts showing up in the NWP can be expected soon.

     

    Hi Crewe,

     

    Good call - I would expect (*IF* the MJO forecasts backed by most models get to Phase 7) the models to be showing different scenario's by early next week & the work done by Judah Cohen & his team for a colder winter than usual to start to rear it's head within the modelling outputs.

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    Model Output Discussion - The Start Of Winter

    in Forecast Model Discussion

    Posted

     

    Hi Snowman,

     

    Yes, although some of them are heading for the "Circle of Doom" which you don't want. A rinse & repeat scenario of mush.

     

    We have support though, even from MOGREPS-G Ensemble System:

     

    UKME_phase_23m_full.gif

     

    And the MOGREPS-G Control Run:

     

    UKMA_phase_full.gif

     

    We also have support from: Global Ensemble Forecast System (NCPE):

     

    NCPE_phase_21m_full.gif

     

    NCEP Global Bias-Corrected Ensemble Forecast System:

     

    NCPE_BC_phase_21m_full.gif

    Along with others...

     

    What we don't want to see is the "Circle of Doom" scenario.

     

    Lets see if we can get to Phase 7, and establish some blocking in areas that favour a more "cold" outcome.

     

    JanuaryPhase7All500mb.gif

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    Model Output Discussion - The Start Of Winter

    in Forecast Model Discussion

    Posted · Edited by Dr. Astro

    Possible heights building towards Greenland from NE Canada perhaps around the 3rd week, or I'm I misinterpreting those charts?

     

    Hello Hocus Pocus,

     

    No, that is correct what you are saying. It generally merges with the Azores High, with height's moving towards Greenland. It can also link up with any Scandinavian High too.

     

    If one is seeking cold & snow, this is an ideal situation.

     

    hgt500-anomaly.png

     

    The charts continue to chop and change, and I must add this makes a very interesting time to be model watching...

     

    Somethings brewing, one thinks.

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    Model Output Discussion - The Start Of Winter

    in Forecast Model Discussion

    Posted

    Good morning all,

     

    Following on from OldMetMan's comments regarding the NWS discussion, i'd like to add some further information.

     

    I'll try and keep this as simple as possible.

     

    Firstly though, the current weather situation we have here in the United Kingdom, or "reliable timeframe" as it's commonly known as.

     

    This week, Monday to Thursday is looking rather benign, dry, some sunshine and feeling chilly, especially at night time, where frosts may accumilate in favourable places.

     

    We can see this from the following charts: (I'll be using the GFS to illustrate in the reliable time frame, as most models agree unanimously)

     

    Tuesday

     

    hgt500-1000.png

     

    ukmaxtemp.png

     

    Wednesday

     

    hgt500-1000.png

    ukmaxtemp.png

     

    Thursday

     

    hgt500-1000.png

    ukmaxtemp.png

     

    So, we can see from the above charts (MAX Temperatures) that it will feel rather chilly, especially after the mild(ish) weather we have been accustomed to as of late.

     

    The 500-1000hPa charts are of good use, these measure how warm, or how cold a layer is in the atmosphere. Thickness charts are a good way to measure the probability of snow, or other prospects like warm/cold air.

     

    The change is coming in from our North West of the United Kingdom, and we can see by Thursday night.

     

    h850t850eu.png

    We can see on the T850 chart, which measures the upper air temperature's and becomes instrumental to what we recieve on the ground, so to speak. It's also another good tool to use for deciding if you will get snow or not, and the general rule is:

    (Maritime flow)

    Sea Level: -7c

    150m: -6c

    300m: -5c
    450m: -4c
    600m: -3c
     
    I say "General Rule" as it can be different depending on what else is happening weather wise.
     
    So, anyways, we can see from the following thickness chart on Friday there is potential for snow, albeit mainly at elevated levels.
     
    hgt500-1000.png
     
    The above chart is the 500-1000hPa. What we are looking for here is the "528 DAM Line" or 528 Dacameters. We want this to be as south as possible if you are looking for cold/snow.
     
    The 850's are showing at -5C.
     
    h850t850eu.png
     
    Using the rule we learnt earlier, places above 300-400m could see some snow.
     
    We can see from the Snow Risk chart below as the front pushes in, NW Scotland and higher ground 400m + is ideal for snowfall.
     
    uksnowrisk.png
     
    After this time frame, we are really getting into the unreliable time frame, but it's always nice to check what the charts are showing within the reliable timeframe, as people tend to get carried away with silly posts like:
     
    "No cold for the next 4 weeks"
    "No mild weather for the next 4 weeks"
    "No snow in December"
    "Charts are crap"
     
    Etc etc, you get my point. If anyone can tell you with 100% confidence what the weather will be like in 4 weeks time, then they should be working for NASA/UK Met and running the company. Oh, and placing lottery numbers too.
     
    As I mentioned at the start of the post to go on from what OldMetMan was talking about, we can see as per comment from NWS:
     
     

    A SECOND FEATURE OF THE PACIFIC---IS THE EARLY EMERGENCE OF THE
    SUBTROPICAL JET...AND ACTIVE OVER NORTHERN MEXICO SO EARLY IN THE
    LOW-SUN HALF OF THE YEAR. THIS IS USUALLY MORE A LATE JANUARY
    THROUGH FEBRUARY OBSERVANCE

     

    We can see where the Jet is at the moment in Mexico which attributes to the post above, it usually isn't their at the moment.

     

    post-22913-0-04090200-1417521275_thumb.p

     

    Maybe this does mean a large pattern distruption, I am not sure, but will have a good look at the charts and data available to us and decide from there.

     

    If we look at the forecast for the Jet we can see it remains very strong for 14/12

     

    hgt300.png

     

    But after this is where the NWS discussion and what OldMetMan was talking about might change, around the 17th as we see a strong surge from the Jet over Mexico at 180 hours.

     

    post-22913-0-00872800-1417521685_thumb.p

     

    Which looks on course for Central USA & should start to impact upstream around the 17th.

     

    Remembering the Jet Stream from earlier, and how powerful it was, we can see around the time of impact C.USA we have a slack Jet coming from Canada and southerly digging:

     

    hgt300.png

    I am unsure if this is related, but will post again when I have done some research.

     

    Another thing to keep an eye out on is the potential storm, at the moment it's hitting Scotland, and Western Isles, but needs an eye kept on to track and see how it unfolds, but that's for another post, maybe.

     

    Regards,

     

    Dr. Astro

     

     

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