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Model output discussion - here comes the beast!


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Posted
  • Location: Coalville
  • Location: Coalville

    Forgive me as im totally new to this forum.  I've just been looking at Ventusky using its GEM model, to see what the cold spell might do and wow, i found a minus -24C in the highlands of scotland by 6AM next Friday morning(selecting 2m above surface). Could we even see a possibility of an all time record broken and what is the march record low? GEM did not have temperature data for higher levels, so maybe its even colder in higher locations???  Exciting stuff.

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    Early guidance forewarning of next weeks weather was issued earlier on, and this has been further enhanced with extended outlooks in bulletins. AFAIK (comms not being my area) public agencies and majo

    Come on those looking for the breadown before the major cold and snow has begun You will be very lucky if that is the correct word to see this in ANY winter in the rest of your lives I would sugg

    Microscale detail absorbing an awful lot of attention on here, when in reality it is a waste of emotion. The macroscale pattern is now fixed - it will not change significantly now for the start of nex

    Posted Images

    Posted
  • Location: Darlington
  • Weather Preferences: Warm dry summers
  • Location: Darlington
    4 minutes ago, Thesonofhendrix said:

    Forgive me as im totally new to this forum.  I've just been looking at Ventusky using its GEM model, to see what the cold spell might do and wow, i found a minus -24C in the highlands of scotland by 6AM next Friday morning(selecting 2m above surface). Could we even see a possibility of an all time record broken and what is the march record low? GEM did not have temperature data for higher levels, so maybe its even colder in higher locations???  Exciting stuff.

    8

    The March record low is -22.8c in 1958

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    Posted
  • Location: Somerset midway between Bath&Wells. Mendips 200m asl
  • Weather Preferences: Snow and lots of it or warm and sunny, no mediocre dross
  • Location: Somerset midway between Bath&Wells. Mendips 200m asl
    46 minutes ago, abbie123 said:

    I no most will get some snow but southern England looks like it’s going to get buried...:cold::cold::cold:

    623DC2D9-3990-46ED-B305-216B0C922C41.gif

    Gutted. Truly gutted.

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    Posted
  • Location: Grays, Thurrock
  • Location: Grays, Thurrock

    after having look through all gfs ensemble they all crackers to t-192. closest to the ukmo I cold see was number 18.

    Modele UKMO - Carte prévisions

    gens-18-1-150.png

    gens-18-0-156.png

    then this at 192. 

    gens-18-1-192.png

    low in Atlantic on  Ukmo is actually further East and disrupting more at 144 so we may miss the blizzard and just continue pull copious amounts of snow from the north Sea  as it moves off north East and joins the vortex in FI which is dropping down much further east on UKMO. how about a eastern European Vortex?? lol

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    Posted
  • Location: Nottingham
  • Location: Nottingham

    I think there can now be quite high confidence in a bitter east wind next week starting late Sunday or early Monday 

    This really does look like it could be a historic late winter (early spring) spell - certainly for cold and windchill but most likely snow ( for some )

     

     

     

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    Posted
  • Location: pelsall, 500ft asl (west mids)
  • Location: pelsall, 500ft asl (west mids)

    Is this really happening ????

    upgrades every day for the last ?7 days ,...,,

    spring looks a long way off!!!

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    Posted
  • Location: NR LOURDES SW FRANCE
  • Location: NR LOURDES SW FRANCE

    If you’re going to get low pressure trying to move ne towards the UK you don’t want to see a ball shaped low, a shallow more elongated feature which is more likely to keep the cold air intact and bring some frontal snow before sliding east .

    And here’s the deal the bellwether  for extending the cold is for any frontal  snow to not make much inroads into the UK because if it does that suggests the block is too weak or a west based negative NAO is setting up.

    Hopefully there’s no need to rely on the riskier frontal snow scenario too early in the cold spell.

    Edited by nick sussex
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    Posted
  • Location: Darlington
  • Weather Preferences: Warm dry summers
  • Location: Darlington

    12z GFS ens control on the cold side of the mean bitter next week maybe a bit less cold during the 1st full week?

    graphe_ens3_euk4.thumb.gif.bab2f3611818f7eac0a06fd17fd4f0e3.gif

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    Posted
  • Location: Wirral, Merseyside
  • Weather Preferences: Snow, Sunny crisp frosty days & Thunderstorms
  • Location: Wirral, Merseyside

    What's that coming over the hill is it a monster? Is it a monster?

    YES

    UN120-21.thumb.GIF.0de2b9ed457bf3c21ff10a23333294ef.GIFUN144-21.thumb.GIF.11cfd54b568a87a01fff560ea155b22d.GIF

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    Posted
  • Location: Waddingham, Lincolnshire. (9m asl)
  • Weather Preferences: Anything newsworthy, so long as it's not in the Daily Express
  • Location: Waddingham, Lincolnshire. (9m asl)
    59 minutes ago, Day 10 said:

    gfseu-2-288.thumb.png.ad9a492d633067cf5d5d859ea91a2a25.png

    Waits patiently for someone to mention the word breakdown....

    They'll certainly be plenty of those if today's charts don't verify...and probably a few on the roads if they do.

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    Posted
  • Location: New Forest (Western)
  • Weather Preferences: Fascinated by extreme weather. Despise drizzle.
  • Location: New Forest (Western)
    21 minutes ago, carinthian said:

    Evening all, truly remarkable charts this evening. We have out coldest Day as Tuesday with a max of -14c in the village and a minimum of -20c on Wednesday morning. Thursday will see the deepest of cold air over the British Isles with some parts of England and Wales remaining below freezing all day. I highlight the chart below at 162t and you will notice the circulation  forming over Poland/ Southern Baltic ( : as mentioned in the above post from yesterday ) It is from this our experts think will produce some heavier snowfall in Eastern Britain towards the end of next week. Still early days ,but this system is now being progged as shown by the attached chart from GFS . Interestingly, they also mention a further even more intense cold pool for early March to move down from the Russian Arctic. Wow. March record cold on the cards.

    C

    GFSOPME12_162_2.png

    Goes without saying really but huge thanks for the insight Carinthian :good:

    As you say, Thursday the latest consensus for the coldest day in the UK. GFS maximums impressive given this is having overlooked the probable lying snow across inland parts of Southern England (chart included purely for reference).

    Netweather GFS Image uksnowdepth.png

     

    The part of your post I've put in bold may leave some in the west feeling less cheerful on the face of it, but reading in between the lines, it suggests LP getting further E than the 12z GFS and 00z ECM op runs have shown us before any attempt to pus north, which improves the chances of staying within the deeply cold air as it slowly but surely destabilises; I can see the longer-term result from that being more widespread snow than in the scenario of a direct attack of LP from the south.

     

    As for the even more intense cold pool for early March, well that is fascinating as it sounds like even weak Scandinavian ridges may be sufficient to keep the imports coming from well to the east? Either than or one heck of a Greenland block is expected and not west-based for that matter?

    If you can't give away such details I will understand, but I feel  it's worth a try :D.

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    Posted
  • Location: Liphook
  • Location: Liphook

    Both the GFS and the UKMO are really exceptional runs, you could perhaps say the GFS introduces a touch too much milder air deep into FI with that low but its so far out I suspect the GFS will eventually modify it further south anyway.

    The UKMO though, my word that maybe the perfect easterly flow I've ever seen, and there have been some corkers this week that is for sure!

    26-27th look broadly locked and loaded now, so we will have a 48hr period with easterly winds and snow showers, probably lots in favoured locations and then there looks likely to be some feature that will travel in from the NE to give inland areas a taste of the action.

    Edited by kold weather
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    Posted
  • Location: Catchgate, Durham,705ft asl
  • Location: Catchgate, Durham,705ft asl

    ECM 72hrs.

     

    Bluearmy approaching from East,closely followed by Purplearmy.:D

     

    ECM0-72.thumb.GIF.4b5603e13337a3b949a6d4657bc587ff.GIF

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    Posted
  • Location: Saffron Walden, Essex
  • Weather Preferences: Warm summers, Snowy winters.
  • Location: Saffron Walden, Essex
    1 minute ago, Paul said:

    I think we may need to add some new colours to the scale on these maps!

    newscale.png

    Is that `below average` Paul? I presume it`s not T2 temps...

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    Posted
  • Location: HILL OF TARA IRELAND
  • Weather Preferences: SNOW ICE
  • Location: HILL OF TARA IRELAND
    1 minute ago, Paul said:

    That's correct.

    Grey  then white I think that is the coldest colours.

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    Posted
  • Location: New Forest (Western)
  • Weather Preferences: Fascinated by extreme weather. Despise drizzle.
  • Location: New Forest (Western)

    UW72-7.GIF?22-18 ECM0-72.GIF?22-0

    ECM has slightly lower uppers out east. Let's see what it can do with those...

     

    Edit: +96 is spot the difference;

    UW96-21.GIF?22-18 ECM1-96.GIF?22-0

    That shortwave by Iceland is better defined but has moved mostly to the west since +72.

    Trough across Italy is in place and at about the same minimum pressure so that's good.

    Azores low also very similar and with that handy disruption on the E side; merger of this with the Italian trough on the UKMO 12z at +120 tightens the flow and pulls deeper cold west compared to what would occur otherwise.

    Edited by Singularity
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    Posted
  • Location: West Sussex
  • Weather Preferences: Extreme cold & snow
  • Location: West Sussex

    UKMO at 144hrs is **#!$xing well RIDICULOUS !

    image.thumb.png.6b27e42e809e98a6c1e3eda16ddb6d9a.pngimage.thumb.png.889ec760ff667bb6b7c328e24234c703.pngimage.thumb.png.2cf969dd4282e1d7ba5190579f40a3a7.png

    :cold::cold::bomb::blink2::clap:!!!

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    ENTRENCHED COLD AND CONVECTIVE EASTERLIES

    Just a briefer (for me) interim post before my Eurasia temperature, sea surface temperature and snow cover report due later tomorrow. During the last few days I noticed some concern from a few posters about less cold air moving in from the south. I've also seen a few misconceptions about convective easterlies. Part of this is very understandable as we've seen so few "proper" long fetch easterlies in the last 30 years. I was fortunate enough to witness many of them back in the '60s to '80s and I'll pull out some charts from the archives and compare them to a couple shown in the current model output. I hope to allay some of those concerns. 

    Let's look at last night's ECM 0z run. It ends with the charts below. One might conclude that the LP will push in some much milder air from the south or south-west. If this had followed a brief and transient easterly with an active Atlantic jet stream then normal service would be quickly resumed. The current set up couldn't be more different. As many have alluded to and I covered in my long post last night (on page 64), the flow reversal from the sudden stratospheric warming is producing persistent HLB, a blocked Atlantic and a weaker jet stream with the main energy diverted well to our south. Exceptionally cold uppers and surface cold are surging south-westwards from Siberia. A deep pool of cold air is developing over Europe. It's a good thing that "some" of this deep cold is moving to our south as well as heading right across us. On this ECM run, just a couple of days earlier, almost all the UK is under sub -12c 850s with values rather lower than that in the east and south-east. Surface temperatures are sub zero. Without a powerful jet stream, this cold block becomes extremely difficult to shift. If it does come under attack from the south or south-west, the incoming LPs often stall and fill up in situ or they can be deflected away north-westwards or south-eastwards. Sometimes the milder air is lifted above the cold block and a classic undercut occurs which can lead to some of our severest blizzards in southern England and the west country. I'm not saying that this would occur this time and a repeat of the famous February 1978 blizzard, although quite possible, is not that likely. Rather more likely is that there will be some enhanced snow shower activity and perhaps some more general snowfalls. It will not matter that the coldest uppers are temporarily mixed out and pushed back slightly north-eastwards. The deep surface cold should remain in place. Very rarely, this set up can produce a period of freezing rain or even an ice storm (eg: January 1940). It's possible that temporarily less cold air can make it into the far south and south-west with a short-lived thaw there. The deep cold then quickly re-establishes itself. This scenario played itself out time and time again in both of the epic winters of 1947 and 1962/63. The cold block maintained itself against almost all onslaughts. There are so many great examples but I'll just pick one from each winter with just before and just after comparisons.

                 ECM  0z T+240 Pressure                          ECM  0z T+240 850s    

    ECE1-240.GIF    ECE0-240.GIF     

                      Feb 3rd 1947                                                Feb 3rd 1947                                                Feb 6th 1947                                             Feb 6th 1947  

    archives-1947-2-3-0-0.png    archives-1947-2-3-0-1.png     archives-1947-2-6-0-0.png    archives-1947-2-6-0-1.png 

                        Jan 6th 1963                                               Jan 6th 1963                                              Jan 12th 1963                                           Jan 12th 1963

    archives-1963-1-6-0-0.png    archives-1963-1-6-0-1.png     archives-1963-1-12-0-0.png    archives-1963-1-12-0-1.png

    If you wish to run through these archived charts, here's the link:  http://www.meteociel.fr/modeles/archives/archives.php?mode=2&month=2&day=3&year=1947&map=0&type=ncep

    Although there were minor early and mid-winter stratospheric warmings in the 1962/63 winter, there was no SSW and no flow reversals.  With the upcoming cold spell we have a powerful reversal which is very likely to make the HLB and the cold block even more persistent. Another matter to consider is that at times the blocking may shift a little. Several of the recent model runs have suggested periods where the Greenland HP becomes more dominant. This might cut of the easterly source for periods and allow for one or two Arctic incursions. In many past severe winters, there are many examples of easterly flows backing to the north and then veering into the east again. Now, I know that there will be some more concerns that this will shorten or dilute the cold spell but let me provide some more reassurance here. Firstly, this is not a case of a northerly with the HP toppling and allowing the Atlantic in through the back door and around the top of  it - again due to no strong jet stream being available to shift the cold pattern. Any toppling will simply be for the HP to re-link with the Scandinavian and Russian HPs. This happened on many occasions during both of those epic winters and in many others too. The Arctic has record low sea ice build up (for example less than 60% of the extent in February 1963) but there is still sufficient cold available. After my Eurasia temperature report, I'll do one of my Arctic profile reports over this weekend. Overall a northerly would be less severe than an easterly but I believe only a temporary interruption to the easterly (or north-easterly) re-asserting itself.  Once our cold pool is established, northerlies can deliver some quite potent and snowy weather too. 

    Now a few words about convective easterlies. As many have pointed out, the two main ingredients are sub -8c 850s (ideally sub -10s) and a correctly aligned air flow not too close to the HP. As the whole country seems likely to be under sub -12s for a while, this should not be an issue. With this easterly likely to persist for many days, there will be minor variations mostly between east-south-easterly and east-north-easterly. So different spots would be favoured at different times. An east-south-easterly could push snow showers into eastern England and Scotland from around Norfolk northwards. A rare "Channel" streamer could deliver frequent snow showers to the south coast from around the Isle of Wight down to Cornwall (including me!). A direct easterly would still favour these spots but also include the south-east coastal areas, the Thames estuary (a possible Thames streamer would push showers right through London) as well as Essex and Suffolk.. A little more to north of east would favour all of the east coast with several streamers possibly setting up.

    If we get a clean and strong easterly, then the Baltic Sea and North Sea really come into play. I'll cover those sea surface temperatures in my Eurasia temperature report tomorrow. This can be the equivalent of "lake effect" snow. Very cold  and dry (with low dew points) upper and surface air moves out over the warmer waters and the surface layers rapidly become unstable and the air stream is moderated. Low level convection occurs and cloud and snow showers form quickly. These patterns can produce almost continuous shower activity for many hours or even days, with extraordinarily large snow accumulations. This is not the thread for mentioning details of these events. I can remember many examples from the '60s. In many of those winters, the Baltic actually froze over. Once this happened, it enhanced the deep cold pool but reduced the shower activity with the warmer water supply being cut off. The same used to occur more frequently with the Great Lakes in North America, which rarely freeze fully these days. I haven't even mentioned minor disturbances, troughs and short-waves which can crop up at any time and produce bands of much more continuous snowfall. All of the above + undercuts and blizzards are possibilities in this severe cold spell but we'll need to watch the very short range forecasts for the details.

    Finally, something that is very widely misunderstood about convective easterlies. This is "low level" convection often with cloud tops below 10,000 feet. Normally as we move from Winter into Spring, with the sun getting much higher in the sky and heating up the land surfaces far more than in mid-winter, a cold showery air stream would become very unstable as it crosses the warming land. This can build up huge cumulo-nimbus clouds towering up to 25,000 feet or more, not far off their summer levels. This is associated with north-westerlies, northerlies or north-easterlies with a long or very long sea fetch and then hitting the warming land surfaces. Easterlies simply do not produce the same type of convection except perhaps in the far west and north-west after a longer land crossing. The low level convection is unstable enough to produce significant snowfall but do not think that just because it's nearly March that we'll see, for example "thunder snow" (except if the wind backs towards the north or a trough produces sufficient temperature contrasts). In the 2013 cold spell, even into April there was surprisingly little shower activity. the winds were more from just north of east during that spell. There was a brilliant paper on low level convection published about 30 to 40 years ago but I could not find it in my quick search. Perhaps as convective easterlies have become so rare, there hasn't been so much interest in them. When I find it, I'll provide a link in a future post. 

     

    Edited by Guest
    Correct typos and check charts
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    Message added by Paul

    Please only post model discussion in this thread 

    For more general chat and banter, or moans and ramps loosely around the models, please head to the banter thread:
    https://www.netweather.tv/forum/topic/86721-model-moans-ramps-and-banter/

    For general weather chat including about the snow/cold chances around the country, please go to the regional threads:
    https://www.netweather.tv/forum/forum/142-regional-discussions/

    We also have a special post SSW cold spell discussion open here:
    https://www.netweather.tv/forum/topic/89358-ssw-related-cold-spell-will-it-wont-it/

    Thank you!

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