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Model output discussion - Into 2021


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I have had a good look at the strat charts this morning and there appears to be a lot of guesswork as to how the SSW may affect the trop.  All indications to me are that we have a good propagating eve

The ongoing strength of the HP anomaly over Kara/Ural region is notable. And still EPS is flagging an ongoing North Pacific / Aleutian Low setup. Can’t remember seeing such a sustained pattern like th

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Posted
  • Location: Alston, Cumbria
  • Weather Preferences: Proper Seasons,lots of frost and snow October to April, hot summers!
  • Location: Alston, Cumbria
    1 minute ago, Allseasons-si said:

    Just for fun at that range but the gfs/p is going for another surge of height's into Greenland.

    gfsnh-0-354.thumb.png.2034488b31cc15c4022e9b0cac67d185.png

    Yes, but you want that Greenland High to stretch across to the strong High over Russia with low-pressure (not high-pressure) to the south and south-west of Britain to set up for something extremely interesting! The warmer-than-usual Norwegian Sea has consistently been the "Weakest Link" in the (hopeful) High Latitude Blocking chain- its warmth has consistently attracted depressions into the area which- in turn- has the effect of cutting off supplies of Arctic or Russian air to Britain ☹️!

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    Posted
  • Location: Suffolk
  • Weather Preferences: Snow,snow,snow and if not erm....SNOW
  • Location: Suffolk

    image.thumb.png.fca758c572c6654e4efc55a49394e09b.png 👀 What a cracking pair of lobes!

     

    Edited by Snowmut
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    Posted
  • Location: Ventnor, Isle of Wight
  • Weather Preferences: Anything other than drizzle
  • Location: Ventnor, Isle of Wight
    11 minutes ago, Harsh Climate said:

    Just goes to show you don't need a huge cold pool to the east or north east to get hammered before an upcoming cold spell.

    Look at how mild russia and scandinavia was on the 19th nov 2010, then how cold it was just 27th november 2010, the SSW event in itself brought the cold air in, rather than it already been there to tap into.

    AVN_1_2010111900_2.png

    AVN_1_2010112700_2 (1).png

    I agree...but that's not showing or anything like that now. I'm not contesting what's possible anything is including milder conditions but I'm merely saying so much gets blown up with out any fact or evidence. 

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    Posted
  • Location: Alston, Cumbria
  • Weather Preferences: Proper Seasons,lots of frost and snow October to April, hot summers!
  • Location: Alston, Cumbria
    Just now, CreweCold said:

    With all due respect, I read your winter forecast and it didn't even mention the risk of the spell we're seeing now. In fact, from memory, I think you went mild, wet and windy. 

    You obviously have a good grip on the fundamentals but the weather makes fools of us all.

    @CreweCold  Lets say I was presently surprised. Indeed the predicted SSW high over the Arctic is not what I expected, given that the Stratospheric Westerlies along 60N were almost record- strength in late November when I produced my forecast!

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    Posted
  • Location: Reigate Hill
  • Weather Preferences: Anything
  • Location: Reigate Hill
    13 minutes ago, iapennell said:

    Firstly, a Happy New Year to Netweather Forum members and those eagerly watching the charts hoping for a very cold and snowy synoptic set-up.

     

    Thanks for your thoughts. This is def a one-off SSWE with maybe very few events helping us to predict how it will go let alone the trop setup as you detailed? I am not brave enough to call it, but I suspect, as normal with the UK, if we are to get a severe cold spell we will need some luck and some shuffling of the pack!

     

    Edited by IDO
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    Posted
  • Location: South Oxfordshire
  • Location: South Oxfordshire
    36 minutes ago, IDO said:

    Looking at the gefs at d8 something is happening and if this is not a rogue suite then it is very interesting. The op seems tame compared to some of the members:

    gens_panel_bsh0.png

     

    Is this what @MATTWOLVES was alluding to earlier? 🤔 

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    Posted
  • Location: Drayton, Portsmouth
  • Location: Drayton, Portsmouth

    Back to the next couple of weeks ... The GEFS continues to trend the mean back to something less cold after the 12th BUT a close inspection of ensembles suggests members with SWlies + Atlantic return are no more numerous than those with colder evolutions, even in the days afterwards. I'd suggest the ensembles are still searching for the solution from D9 onwards, and not making a definitive comment on the direction of the D10-D15 period, as yet.

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    Posted
  • Location: Chapmanslade, Wiltshire + Charente, France
  • Location: Chapmanslade, Wiltshire + Charente, France
    1 minute ago, Anthony Burden said:

    The met guys are apparently watching the possible development of the Icelandic low

    dropping down from the northwest with a very keen eye,possibly destructive white

    stuff next weekend.

    I assume you mean disruptive rather than destructive ?

    What is the source of this information in the Met ?

    9 minutes ago, IDO said:

    Thanks for your thoughts. This is def a one-off SSWE with maybe very few events helping us to predict how it will go let alone the trop setup as you detailed? I am not brave enough to call it, but I suspect, as normal with the UK, if we are to get a severe cold spell we will need some luck and some shuffling of the pack!

     

    What do you mean by 'one off SSW'?

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    Posted
  • Location: North East Hampshire
  • Location: North East Hampshire
    4 minutes ago, Anthony Burden said:

    The met guys are apparently watching the possible development of the Icelandic low

    dropping down from the northwest with a very keen eye,possibly destructive white

    stuff next weekend.

    Which Met guys? Do you have a link please?

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    Posted
  • Location: Whitefield, Manchester @ 100m
  • Location: Whitefield, Manchester @ 100m
    21 minutes ago, iapennell said:

    Firstly, a Happy New Year to Netweather Forum members and those eagerly watching the charts hoping for a very cold and snowy synoptic set-up.

    The weatheriscool website offers a forecast for mean winds to be up to 25 metres/ second (over 50mph) from the East along 60N by the 18th January, and given the tendency for Sudden Stratospheric Warmings over the Arctic (and the associated circulation) to work downwards into the troposphere over the following three weeks this does offer hope of a frigid easterly blast in early February. BUT...

    1) The QBO in November (at the 30 mb level in the stratosphere high over the Equator) was on average over 11 metres/second (24 mph) from the West.

    2) Most of the Equatorial waters are hotter than usual, even though there is an East/ Central Pacific La Niña (the worst possible place for Westerly AAM considerations as it strenthens the tropical easterlies to the west but any westerlies aloft wont touch the Peruvian Andes to be dissipated). A hotter-than-usual Equator overall means an active Intertropical Convergence Zone (ITCZ) and a healthy ITCZ means stronger north-easterly Trade Winds further north- busily pumping Westerly Atmospheric Angular Momentum (AAM) into the Northern Hemisphere general atmospheric circulation (thereby also increasing the sink for Westerly AAM elsewhere). 

    3) The Norwegian Sea and Barents Sea remain free of ice and are warmer than usual- as is the North Atlantic, but Canada/ Greenland are already very cold. This not only fosters cyclonogenesis in the north-west Atlantic but warmer-than-usual waters further east and north wont discourage the depressions moving into those areas.

    4) There have been Westerlies over the Tibetan Plateau- up to 20 mph in recent days. But this is not enough to negate the Westerly AAM- increasing effects of 20 mph (and above) North East and Easterly Trade Winds most places between 30N and the Equator (which you can see from "Windy" website).

    Much Westerly AAM is being generated by North East Trade Winds, some of which will be offset by surface Westerlies over the Equatorial Indian Ocean. But most of the generated Westerly AAM will remain intact even after the sink effects of surface Westerlies over the Equatorial Indian Ocean and the limp Westerlies over Tibet are taken into consideration. The Westerly QBO over the Equator- feeding its influence down from the Stratosphere will add Westerly AAM to the tropospheric Northern Hemisphere circulation. This only leaves higher latitudes of the North Atlantic and North Pacific as sinks for this Westerly AAM- and (given the fundamentals of Canada-Greenland to North Atlantic baroclinicity and sea-surface warmth in the European Arctic) there is a strong likelihood that the UK and points west will be seeing those Westerlies. The Easterlies predicted for the Arctic Stratosphere can only make limited headway against these fundamentals.

    So, on the basis of such meteorological fundamentals, there will not be a January 1987 or a February 1986 style Great Freeze in the UK in Winter 2020-2021. There will (probably) be this coming week and another week in early February with some very cold east winds, some sharp night frosts and snow-showers (as the predicted Sudden Stratospheric Warming feeds its influence downwards) but no month-long freeze with nights below -10C and deep snow across Britain.              

    Sounds good to me. Feb 86 was cold but dry and Jan 87 wasn't that special up north.

    I'd be much more interested if you could tell us if there will be a week long cold snap with a big dumping of snow anywhere, because that's all most of us want every year - one big snowfall. But that's impossible to predict if you are issuing a forecast of global generalities.

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    Posted
  • Location: North East Hampshire
  • Location: North East Hampshire
    1 minute ago, Anthony Burden said:

    Hi Matt Hugo Twitter 

    Ah thanks - I was hoping you meant the Met Office. 

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    Posted
  • Location: Purley, Surrey - 246 Ft ASL
  • Weather Preferences: January 1987 / July 2006
  • Location: Purley, Surrey - 246 Ft ASL
    1 minute ago, Johnp said:

    Ah thanks - I was hoping you meant the Met Office. 

    Not that Matt Office.

    I'll get my coat 🤪 

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    Posted
  • Location: Alston, Cumbria
  • Weather Preferences: Proper Seasons,lots of frost and snow October to April, hot summers!
  • Location: Alston, Cumbria
    8 minutes ago, MJB said:

    I don't quite get your last paragraph ? You say there will be some very cold winds and some sharp night frosts , but no nights of -10c ?? we have been very very close to -10c in this spell , so are you saying we will have a repeat of what we are seeing with regards cold?

    Early February will likely be cold and frosty, on the strength of the Sudden Stratospheric Warming now predicted for mid-January exteme minima across the English and Welsh lowlands will be somewhere between -5C and -10C, some frost-hollow areas are likely to be a bit colder than this. In the Scottish Highland's frost-hollows (places like Altnaharra and Braemar) the extreme minima are likely to be near -15C. However, don't expect widespread heavy snowfall unless you live near the North East and Yorkshire coasts, in the Pennines or in northern/ eastern Scotland.

    For temperatures to get below -10C right across Britain you ideally need three ingredients: Significant powdery snow-cover (over two inches), a very cold airmass in-place, then clear skies and light winds for the duration of at least one night (this leads to strong radiative heat loss). For this to happen you need (firstly) a cold enough airstream to bring widespread powdery snowfall that does not melt, followed by clearing skies and light winds with the very cold air being maintained. I cannot quite see how that is going to happen unless the frigid easterlies have a fetch to as far east as Russia, this lasts three or four days and then high-pressure ridges in from the north or north-east. The Norwegian Sea will likely remain too warm for a direct hit from the Arctic to bring daytime temperatures below freezing across the whole country necessary to sustain powdery snow-cover, a following ridge from a Greenland High will involve air being warmed over the far north Atlantic/ Norwegian Sea (due to northerlies falling light) and that could lead to daytime thaws before the clear still nights set in: Wet snow releases a lot of latent heat as it freezes due to radiative cooling- and such latent heat release, combined with the air above not being especially cold, would likely temper how far air-temperatures could fall.     

    I have a hunch that Westerly influences off the North Atlantic will too soon become (or remain) a little too strong to permit the uninterrupted flow of air from northern Russia to the UK for three or four days that would be needed to establish widespread powdery snow-cover in the first place, let alone for this to then be followed by a high-pressure ridge then extending south-west from Scandinavia (to clear the skies and keep the airmass very cold with an east or north-easterly drift of air) to complete the frigid set-up. 

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    Posted
  • Location: Coventry
  • Location: Coventry

    Is it plausible that the GFS was incorrectly modelling the MJO into phase 3 causing the relaxation of the pattern, where as the ECM keeps it in cod or just edging into phase 2

     

    ECMF_phase_51m_full (1).gif

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    Posted
  • Location: Orpington Kent.
  • Location: Orpington Kent.
    3 minutes ago, iapennell said:

    Early February will likely be cold and frosty, on the strength of the Sudden Stratospheric Warming now predicted for mid-January exteme minima across the English and Welsh lowlands will be somewhere between -5C and -10C, some frost-hollow areas are likely to be a bit colder than this. In the Scottish Highland's frost-hollows (places like Altnaharra and Braemar) the extreme minima are likely to be near -15C. However, don't expect widespread heavy snowfall unless you live near the North East and Yorkshire coasts, in the Pennines or in northern/ eastern Scotland.

    For temperatures to get below -10C right across Britain you ideally need three ingredients: Significant powdery snow-cover (over two inches), a very cold airmass in-place, then clear skies and light winds for the duration of at least one night (this leads to strong radiative heat loss). For this to happen you need (firstly) a cold enough airstream to bring widespread powdery snowfall that does not melt, followed by clearing skies and light winds with the very cold air being maintained. I cannot quite see how that is going to happen unless the frigid easterlies have a fetch to as far east as Russia, this lasts three or four days and then high-pressure ridges in from the north or north-east. The Norwegian Sea will likely remain too warm for a direct hit from the Arctic to bring daytime temperatures below freezing across the whole country necessary to sustain powdery snow-cover, a following ridge from a Greenland High will involve air being warmed over the far north Atlantic/ Norwegian Sea (due to northerlies falling light) and that could lead to daytime thaws before the clear still nights set in: Wet snow releases a lot of latent heat as it freezes due to radiative cooling- and such latent heat release, combined with the air above not being especially cold, would likely temper how far air-temperatures could fall.     

    I have a hunch that Westerly influences off the North Atlantic will too soon become (or remain) a little too strong to permit the uninterrupted flow of air from northern Russia to the UK for three or four days that would be needed to establish widespread powdery snow-cover in the first place, let alone for this to then be followed by a high-pressure ridge then extending south-west from Scandinavia (to clear the skies and keep the airmass very cold with an east or north-easterly drift of air) to complete the frigid set-up. 

    Jeeze 🙂 you don’t want much.. little ole me is scratching around wondering if a patch of -9 uppers will hit the south east next week...:)

    Edited by TSNWK
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    Posted
  • Location: Nr Appleby in Westmorland
  • Location: Nr Appleby in Westmorland

    Model discussion and personal

    forecasts are not the same thing. One off topic post can lead to many more! Please use the right threads. 

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    42 minutes ago, iapennell said:

    Firstly, a Happy New Year to Netweather Forum members and those eagerly watching the charts hoping for a very cold and snowy synoptic set-up.

    The weatheriscool website offers a forecast for mean winds to be up to 25 metres/ second (over 50mph) from the East along 60N by the 18th January, and given the tendency for Sudden Stratospheric Warmings over the Arctic (and the associated circulation) to work downwards into the troposphere over the following three weeks this does offer hope of a frigid easterly blast in early February. BUT...

    1) The QBO in November (at the 30 mb level in the stratosphere high over the Equator) was on average over 11 metres/second (24 mph) from the West.

    2) Most of the Equatorial waters are hotter than usual, even though there is an East/ Central Pacific La Niña (the worst possible place for Westerly AAM considerations as it strenthens the tropical easterlies to the west but any westerlies aloft wont touch the Peruvian Andes to be dissipated). A hotter-than-usual Equator overall means an active Intertropical Convergence Zone (ITCZ) and a healthy ITCZ means stronger north-easterly Trade Winds further north- busily pumping Westerly Atmospheric Angular Momentum (AAM) into the Northern Hemisphere general atmospheric circulation (thereby also increasing the sink for Westerly AAM elsewhere). 

    3) The Norwegian Sea and Barents Sea remain free of ice and are warmer than usual- as is the North Atlantic, but Canada/ Greenland are already very cold. This not only fosters cyclonogenesis in the north-west Atlantic but warmer-than-usual waters further east and north wont discourage the depressions moving into those areas.

    4) There have been Westerlies over the Tibetan Plateau- up to 20 mph in recent days. But this is not enough to negate the Westerly AAM- increasing effects of 20 mph (and above) North East and Easterly Trade Winds most places between 30N and the Equator (which you can see from "Windy" website).

    Much Westerly AAM is being generated by North East Trade Winds, some of which will be offset by surface Westerlies over the Equatorial Indian Ocean. But most of the generated Westerly AAM will remain intact even after the sink effects of surface Westerlies over the Equatorial Indian Ocean and the limp Westerlies over Tibet are taken into consideration. The Westerly QBO over the Equator- feeding its influence down from the Stratosphere will add Westerly AAM to the tropospheric Northern Hemisphere circulation. This only leaves higher latitudes of the North Atlantic and North Pacific as sinks for this Westerly AAM- and (given the fundamentals of Canada-Greenland to North Atlantic baroclinicity and sea-surface warmth in the European Arctic) there is a strong likelihood that the UK and points west will be seeing those Westerlies. The Easterlies predicted for the Arctic Stratosphere can only make limited headway against these fundamentals.

    So, on the basis of such meteorological fundamentals, there will not be a January 1987 or a February 1986 style Great Freeze in the UK in Winter 2020-2021. There will (probably) be this coming week and another week in early February with some very cold east winds, some sharp night frosts and snow-showers (as the predicted Sudden Stratospheric Warming feeds its influence downwards) but no month-long freeze with nights below -10C and deep snow across Britain.              

    would you be kind enough to share your original  winter forecast? Thanks 

    Edited by weathercold
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    Message added by Paul,

    Please stick to discussing the model output in this thread. For more general chat , please use the winter/cold weather/snow chat, banter, moans and ramps thread

    For local cold/snow and weather related chat, please head over to the Regional Area.

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