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Model Discussion Thread - short term

  • 20-11-2011 7:13pm
    #1
    Banned (with Prison Access) Posts: 8,633 ✭✭✭


    Seems we are missing a thread dedicated to the computer models. Think we should start one.

    To christen the thread we have a wonderfully mild ECM run showing little in the way of change for the forseeable future with just the odd incursion of cooler air at times with a hint of frost some nights too.

    Recm1921.gif


    The less said about it the better I think..


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Comments

  • Registered Users Posts: 1,461 ✭✭✭Musicman2000


    Yeah one word disaster :)


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


    Is this not just a duplicate of the FI thread? That chart is for 8 days into the future. I would take model outlook to mean what they're trending towards outside the normal 5-7 day reliability timeframe, i.e. Fantasy Island!


  • Closed Accounts Posts: 3,548 ✭✭✭Harps


    No harm in having a thread for more of a proper look at what's going to happen, leave the FI thread for posting unrealistic eye candy well into the future

    Bit of a disastrous ECM this evening, high pressure around the Bay of Biscay pumping in Atlantic weather all week


  • Closed Accounts Posts: 2,693 ✭✭✭Redsunset


    Yeah we've had this problem in previous years as what to set the FI time frame at.

    To me anything past 120h is FI however in certain conditions it can be 24 h or less


  • Closed Accounts Posts: 3,548 ✭✭✭Harps


    I'd take it simply when the ensemble numbers start to noticeably spread which at the moment is around 120h on the 25th

    graphe_ens4_xtz1.gif


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  • Registered Users Posts: 10,507 ✭✭✭✭dsmythy


    If people could agree to make this a thread for models no more than 7 days ahead or some other figure then it shouldn't duplicate the FI thread.


  • Registered Users Posts: 5,068 ✭✭✭Iancar29


    dsmythy wrote: »
    If people could agree to make this a thread for models no more than 7 days ahead or some other figure then it shouldn't duplicate the FI thread.

    Yeah that seems reasonable... and to be entitled in the thread name maybe? :)


  • Registered Users Posts: 277 ✭✭J6P


    How about renaming this thread.. Model Outlook day 1-7 and the other thread Model Outlook day 7- 14(FI)


  • Registered Users Posts: 2,246 ✭✭✭rc28


    Or how about, just like on other weather forums, we make things simple and have just one forecasting model output discussion?

    Having two threads just adds unnecessary clutter and confusion.


  • Closed Accounts Posts: 5,234 ✭✭✭thetonynator


    I think this is a good idea in one way, i.e. the FI thread is generally for unrealistic charts that rarely or never come off, whereas this is good for the short term discussion. On the other hand, whenever anything remotely interesting comes up we tend to have a dedicated thread for it anyway, so this might not be necessary.

    If the thread is kept specifically for discussion of realistic threads, and not random off topic chat like e.g. the winter thread, then I would say it will work. If it veers towards general outlook (not specifically models) then the thread will lose its purpose.


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  • Registered Users Posts: 836 ✭✭✭derekon


    darkman2 wrote: »
    Seems we are missing a thread dedicated to the computer models. Think we should start one.

    To christen the thread we have a wonderfully mild ECM run showing little in the way of change for the forseeable future with just the odd incursion of cooler air at times with a hint of frost some nights too.

    Recm1921.gif


    The less said about it the better I think..



    Hey Darkman2,

    Given your reputation as a notorious cold ramper (I refer to recent thread about cold from the 16th November onwards that never materialised), I take it you are being slightly sarcastic in the above post?! :D

    PS - are you finding the current period of very mild weather frustrating? Also, I am looking forward to the times this winter when you post your "warnings"....always entertaining and great to see you back on the boards! :)

    Finally, what are your own views on what winter 2011-2012 holds for Ireland? I associate your posts with the winter season for some reason so would be interested to hear your thoughts on the winter ahead...............

    D


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


    I've changed the thread title to diffentiate it from the FI thread. We should use this one for discussing more reliable model output scenarios, and any differences between the different models, rather than the outlandish FI scenarios. Use this one for "homing in" on an upcoming weather event.


  • Banned (with Prison Access) Posts: 8,633 ✭✭✭darkman2


    derekon wrote: »
    Hey Darkman2,

    Given your reputation as a notorious cold ramper (I refer to recent thread about cold from the 16th November onwards that never materialised), I take it you are being slightly sarcastic in the above post?! :D



    Yeah it's sarcasm.:)

    I am not a cold "ramper" btw. I like all sorts of weather. All weather has it's individual moments that I personally enjoy. Still i'd rather see something more interesting then what is currently forecast.


    Rampant Jet Stream, Polar Vortex in the wrong place - preferably it (the blues and purples) should really be over Scandinavia and little in the teleconnections to be overjoyed at either because the AO and NAO across the board look like staying in positive territory for the time being reflected in the synoptic charts, high pressure to the South - low pressure to the North.

    Hopefully the PV will weaken or move and the Jet Stream will amplify. We need everything to slow down. It's too fast. With the PV anywhere over Greenland and we ain't unlocking the door to cold weather. Hopefully we will eventually get some pressure rise there.

    Things can change quickly though as we know. Forecast could be completely different tomorrow.:cool:


    Max temperatures of 4 - 6c on Friday with a hard frost Friday night?

    Rtavn1142.png

    P.S derekon for the Winter ahead (i do dislike Winter forecasts btw - others here trust them more then I do) my own opinion is that it will be a cold Winter overall with plenty of ice and snow and that sort of craic but later in the season then last year. Can't see that kind of a major change until well into December at this stage. I am not confident about that. Just a feeling I have about it. MT goes into these forecasts in some detail. My advice would be to take his advice;)


    The 18z GFS tonight is not too bad btw. Some encouraging signals early in the run for coldies.


    Just an example from the 18z run of what we want to see. High pressure in the Atlantic anchored from Greenland means happy days! (although this is not perfect it's a good sign just to see it)

    Rtavn2401.png


  • Moderators, Society & Culture Moderators Posts: 12,592 Mod ✭✭✭✭riffmongous


    Aw, I thought there was going to be a discussion on the actual models themselves and the physics/computing behind them :(


  • Registered Users Posts: 10,507 ✭✭✭✭dsmythy


    darkman2 wrote: »


    Max temperatures of 4 - 6c on Friday with a hard frost Friday night?

    Rtavn1142.png

    Looks like a chart that would bring a nippy day alright. 12Z ECM similar. Has it slightly milder from the south west.

    11112512_2012.gif


  • Closed Accounts Posts: 3,548 ✭✭✭Harps


    A pretty standard and non eventful few days ahead but still a chance of a decent storm on the 25th, tonight's GFS has it tracking north and only really intensifying once it passes Scotland but some runs have had it as far south as southern England so no real agreement as of yet. A glancing blow on the 18z

    111124122018.gif

    The Shetland Isles get a real battering on tonight's run though, >78 knot winds

    111125002018.gif


  • Registered Users Posts: 356 ✭✭Strangegravy


    Just a quick question.

    The current GFS Europe run has this 850 temp chart for next Friday:

    gfstemps850fri25th.png

    with this 500-1000 chart:

    gfs5001000fri25th.png

    Just from what I've picked up on here, I've been following the temp charts looking for the -5 to -8 uppers for snow, but someone mentioned that if we're under the 528 line, like on the second chart above, that we'll get snow as well.

    Just so I'm clear, do these two charts have to correlate as in -8's and the 528 line, or would those -4 uppers bring us snow because we're under the 528 line?

    Just curious, thanks in advance! :)


  • Registered Users Posts: 9,603 ✭✭✭Birdnuts


    darkman2 wrote: »
    Seems we are missing a thread dedicated to the computer models. Think we should start one.

    To christen the thread we have a wonderfully mild ECM run showing little in the way of change for the forseeable future with just the odd incursion of cooler air at times with a hint of frost some nights too.

    Recm1921.gif


    The less said about it the better I think..

    A dream run if it was a summer month - sadly we can't seem to manage such set-ups when their wanted and at this time of year its simply a waste:(


  • Registered Users Posts: 366 ✭✭doccy


    Birdnuts wrote: »
    A dream run if it was a summer month - sadly we can't seem to manage such set-ups when their wanted and at this time of year its simply a waste:(

    Absolutely, was just thinking that myself. This mild spell would have been stunning in summer months.
    The weather is totally out of kilter. It leads me to believe that we will have a serious cold snap, probably late in the season. Still it wouldn't be a great shock to have a wet mild winter either. Even if the weather was turning colder year on year, statistically a random mild winter would be annoying but not unexpected.


  • Registered Users Posts: 2,671 ✭✭✭Rougies


    Just a quick question.

    The current GFS Europe run has this 850 temp chart for next Friday:

    with this 500-1000 chart:

    Just from what I've picked up on here, I've been following the temp charts looking for the -5 to -8 uppers for snow, but someone mentioned that if we're under the 528 line, like on the second chart above, that we'll get snow as well.

    Just so I'm clear, do these two charts have to correlate as in -8's and the 528 line, or would those -4 uppers bring us snow because we're under the 528 line?

    Just curious, thanks in advance! :)

    Good question Strangegravy. But unfortunately neither sub 528 thickness or sub -5 850 uppers or even both together mean precip will fall as snow. They're just kinda two of the basic minimum ingredients to look for.

    There's a lot of other variables involved, for example where the air is coming from, over what surface and for how long. In this case (the 25th), with the winds coming in over the Atlantic Ocean for many 100s of miles the atmosphere near sea level will be warmed too much by the water for snow to fall at low altitudes. -4 to -6 850's don't stand a chance, even within the 528 dam line.

    An easterly with the same thickness/uppers coming in over cold snow fields of continental europe however could be a different story.


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  • Registered Users Posts: 356 ✭✭Strangegravy


    Rougies wrote: »
    Good question Strangegravy. But unfortunately neither sub 528 thickness or sub -5 850 uppers or even both together mean precip will fall as snow. They're just kinda two of the basic minimum ingredients to look for.

    There's a lot of other variables involved, for example where the air is coming from, over what surface and for how long. In this case (the 25th), with the winds coming in over the Atlantic Ocean for many 100s of miles the atmosphere near sea level will be warmed too much by the water for snow to fall at low altitudes. -4 to -6 850's don't stand a chance, even within the 528 dam line.

    An easterly with the same thickness/uppers coming in over cold snow fields of continental europe however could be a different story.

    Ah ok... Thanks for clearing that up for me!

    I knew it wasn't going to be as straightforward as I was thinking, and just when I thought I was getting an understanding of it all too... :D


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


    Yes, that is why for us, the 850-1000 hPa thickness is a more important value to watch. The 500-1000 hPa is a good first guess, as if that's not right in the first place, then snow is pretty unlikely, though freezing rain still is, if there's a sub-zero layer near the surface. 528 dam is a good first guess, but 522 would probably guarantee snow at sea level, regardless of anything else.

    The 850-1000 thickness shows the mean temperature of the lowest, i.e. the most important, layer of the atmosphere, where the physics comes into play. You could have a very cold mid and upper atmosphere, with lowish 500-1000 values, and even cold 850 temperatures, but it's the boundary layer that is most affected by modification by surface characteristics, and the one that snow must survive in order to reach us intact.

    Have a look at the 850-1000 thickness charts, which are freely available for the GFS and NAE. If we get around 1280 dam or lower, then snow's fairly certain.

    11112109_2106.gif

    One thing to remember though - thickness is related to the average virtual temperature of the layer, which also includes humidity. For the same temperature, a humid layer will have a greater virtual temperature, and hence a greather thickness, than a dry layer. However, the drier the layer, the less chance there is of heavy snowfall. It is therefore a fine balance of looking at several factors at once, which is why things can be so marginal in some cases where some factors would shout snow.


  • Closed Accounts Posts: 5,150 ✭✭✭Deep Easterly


    Birdnuts wrote: »
    Recm1921.gif

    A dream run if it was a summer month - sadly we can't seem to manage such set-ups when their wanted and at this time of year its simply a waste:(

    Looks a little bit too much like the default pattern of the last 2 summers which (to me) were basically pure rot, but each too our own I suppose.


  • Registered Users Posts: 356 ✭✭Strangegravy


    Su Campu wrote: »
    Yes, that is why for us, the 850-1000 hPa thickness is a more important value to watch. The 500-1000 hPa is a good first guess, as if that's not right in the first place, then snow is pretty unlikely, though freezing rain still is, if there's a sub-zero layer near the surface. 528 dam is a good first guess, but 522 would probably guarantee snow at sea level, regardless of anything else.

    The 850-1000 thickness shows the mean temperature of the lowest, i.e. the most important, layer of the atmosphere, where the physics comes into play. You could have a very cold mid and upper atmosphere, with lowish 500-1000 values, and even cold 850 temperatures, but it's the boundary layer that is most affected by modification by surface characteristics, and the one that snow must survive in order to reach us intact.

    Have a look at the 850-1000 thickness charts, which are freely available for the GFS and NAE. If we get around 1280 dam or lower, then snow's fairly certain.

    One thing to remember though - thickness is related to the average virtual temperature of the layer, which also includes humidity. For the same temperature, a humid layer will have a greater virtual temperature, and hence a greather thickness, than a dry layer. However, the drier the layer, the less chance there is of heavy snowfall. It is therefore a fine balance of looking at several factors at once, which is why things can be so marginal in some cases where some factors would shout snow.

    Thank you for that, there's another chart site for me to add to my growing list of bookmarked weather pages!

    I was reading up on that about the humidity, that with less humidity in the air, in certain conditions, that snow could fall even if the temperature was a good bit over zero degrees on the ground, because the flakes lose more heat than they take to melt or something along those lines..


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


    Thank you for that, there's another chart site for me to add to my growing list of bookmarked weather pages!

    I was reading up on that about the humidity, that with less humidity in the air, in certain conditions, that snow could fall even if the temperature was a good bit over zero degrees on the ground, because the flakes lose more heat than they take to melt or something along those lines..

    Yes, and that's where 850 hPa Theta-W values come in!!! But that's for another day!


  • Registered Users Posts: 356 ✭✭Strangegravy


    Su Campu wrote: »
    Thank you for that, there's another chart site for me to add to my growing list of bookmarked weather pages!

    I was reading up on that about the humidity, that with less humidity in the air, in certain conditions, that snow could fall even if the temperature was a good bit over zero degrees on the ground, because the flakes lose more heat than they take to melt or something along those lines..

    Yes, and that's where 850 hPa Theta-W values come in!!! But that's for another day!

    I'll be an expert by the end of it, just need the colder weather now to put everything I've picked up over the year into practice!


  • Registered Users Posts: 6,834 ✭✭✭pauldry


    Had a look at wetterzentrale there and again they are going with a colder end to November. They keep changing their mind.

    Id say cold myself but Im afriad Id jinx it.(too late!:P)


  • Closed Accounts Posts: 2,667 ✭✭✭WolfeIRE


    Brief period of colder weather, with small risk of low level sleet in the northwest and north. Moderate risk of sleet 250m asl in the same regions.

    h850t850eu.png
    uksnowrisk.png

    Much midler conditions again on Saturday

    A similar scenario to Friday is in place for Saturday night/Sunday morn.


    h850t850eu.png
    uksnowrisk.png


  • Moderators, Science, Health & Environment Moderators Posts: 7,144 Mod ✭✭✭✭pistolpetes11


    Sorry cant post the pic as I'm on the ipad but is there not a blocking high in place in this chart , looks like the two HP systems have linked up

    Had to save the pic to fb so I could link it without it being a live image !

    http://www.facebook.com/photo.php?fbid=10150403096339448&l=39981906a5


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  • Registered Users Posts: 5,949 ✭✭✭TheMilkyPirate


    Sorry cant post the pic as I'm on the ipad but is there not a blocking high in place in this chart , looks like the two HP systems have linked up

    Had to save the pic to fb so I could link it without it being a live image !

    http://www.facebook.com/photo.php?fbid=10150403096339448&l=39981906a5

    That's a low pressure system pete


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