Jump to content
Snow?
Local
Radar
Cold?
IGNORED

Model Output Discussion - cold spell to end Autumn


Paul
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/

Thank you!

Recommended Posts

Posted
  • Location: Castle Black, the Wall, the North
  • Weather Preferences: Spanish Plumes, Blizzards, Severe Frosts :-)
  • Location: Castle Black, the Wall, the North

Just a selection of charts from earlier in the incredible 6z with a strong arctic blast later this week and an even stronger  very cold spell towards the end being the main highlights but the other feature that's great to see is the lack of mild mush after this midweek..good riddance.!!:shok::santa-emoji::cold-emoji::D

06_81_mslp850.png

06_84_preciptype.png

06_96_preciptype.png

06_96_uk2mtmpmin.png

06_96_ukthickness850.png

06_102_ukthickness850.png

06_105_mslp850.png

06_105_preciptype.png

06_105_uk2mtmp.png

06_120_uk2mtmpmin.png

06_144_mslp850.png

06_153_uk2mtmp.png

06_153_ukthickness850.png

06_168_uk2mtmpmin.png

06_177_uk2mtmp.png

06_177_mslp500.png

06_201_uk2mtmp.png

06_288_mslp850.png

06_288_uk2mtmpmin.png

  • Like 4
  • Thanks 1
Link to comment
Share on other sites

Posted
  • Location: Leicestershire (hinckley)
  • Location: Leicestershire (hinckley)

You have to say at this stage this seems like a fair representation of where we will see snow cover from the upcoming cold spell and the reason why its been dissapointing the initial low moving across us didnt work out as suggested by the GFS last Friday. If any slider low fails to happen then i can see many places missing out on snow for the time being.

Screenshot_20171204-121515.thumb.jpg.39516f68dc4c1a5f8832c068462a941d.jpg

Link to comment
Share on other sites

Posted
  • Location: Crewe
  • Location: Crewe
7 minutes ago, MKN said:

You have to say at this stage this seems like a fair representation of where we will see snow cover from the upcoming cold spell and the reason why its been dissapointing the initial low moving across us didnt work out as suggested by the GFS last Friday. If any slider low fails to happen then i can see many places missing out on snow for the time being.

Screenshot_20171204-121515.thumb.jpg.39516f68dc4c1a5f8832c068462a941d.jpg

What is the scale roughly for these, as in depth?

Link to comment
Share on other sites

Posted
  • Location: Manchester Deansgate.
  • Weather Preferences: Heavy disruptive snowfall.
  • Location: Manchester Deansgate.
8 minutes ago, captaincroc said:

What is the scale roughly for these, as in depth?

Only place with deep snow is Northern Scotland, other places the Green show 2-5cm roughly, why they have to have mathematical representations for a few cm of snow is anyone's guess, you might as well start having the 500mb height charts in standard index form!!!    Anyway, these charts I find do under do the snow depth totals, while I think the ECM over do them.

  • Like 1
Link to comment
Share on other sites

Posted
  • Location: Wildwood, Stafford 104m asl
  • Weather Preferences: obviously snow!
  • Location: Wildwood, Stafford 104m asl

Much better 06Z, 1st slider misses to west, but keeps us cold, 2nd slider much better than on last few runs

h850t850eu.png

Link to comment
Share on other sites

Posted
  • Location: Wyke regis overlooking Chesil beach.
  • Weather Preferences: Snowfall
  • Location: Wyke regis overlooking Chesil beach.

Nobody should really be surprised by the stunning longer range charts showing on the GFS 06z. Its very simple really. If you stop or dilute the west to east motion of energy long enough. The beast from the east will show it's hand or as in this case a bloomin great fist.

  • Like 3
Link to comment
Share on other sites

Posted
  • Location: st albans
  • Location: st albans
1 hour ago, Man With Beard said:

 

 

After that, well, something I've never seen before. For the third successive run, only 1 cluster between D10 and D15. So either they've given up producing clusters beyond T240, or there's a lot of agreement on what is coming next. Here's the past three runs for 18th December:

 

 

They may have stopped providing them MWB. That’s three consecutive runs doing this. I can only assume that if it isn’t fixed on this evenings outptut that someone from Reading has ‘had a word’

 

Link to comment
Share on other sites

Posted
  • Location: Manchester Deansgate.
  • Weather Preferences: Heavy disruptive snowfall.
  • Location: Manchester Deansgate.
2 minutes ago, bluearmy said:

They may have stopped providing them MWB. That’s three consecutive runs doing this. I can only assume that if it isn’t fixed on this evenings outptut that someone from Reading has ‘had a word’

 

You would have thought that, that's why its best just to describe anything beyond 240 and not post charts, ive learned that and that's all ive been doing lately, however though, its not as inconceivable as I fisrt thought that there could be only one cluster on this run, look at the tight bunching on the London ens - very tight for 10-15d period.

  • Like 3
Link to comment
Share on other sites

Posted
  • Location: st albans
  • Location: st albans
Just now, feb1991blizzard said:

You would have thought that, that's why its best just to describe anything beyond 240 and not post charts, ive learned that and that's all ive been doing lately, however though, its not  inconceivable as I fisrt thought that there could be only one cluster on this run, look at the tight bunching on the London ens - very tight for 10-15d period.

it is

if only that its three runs on the bounce

Link to comment
Share on other sites

Posted
  • Location: st albans
  • Location: st albans

I can see where the idea of a scandi ridge introducing as easterly flow is coming from but the probability output from the ens is far from convincing. No appetite to raise pressure in the area nw of Russia and the momentum for higher slp heading west comes from further south across Russia. Assuming it does push west, at this stage,  it looks to be too far south to do anything other than hold the sceuro troughing in place. That's ok! 

  • Like 5
Link to comment
Share on other sites

Posted
  • Location: Canmore, AB 4296ft|North Kent 350ft|Killearn 330ft
  • Location: Canmore, AB 4296ft|North Kent 350ft|Killearn 330ft
11 minutes ago, Frosty. said:

Those who are expecting most of the uk will miss out on snow later this week and the weekend might get a surprise, with troughs swinging south in the arctic flow that would mean bands of snow showers spreading south so whilst on the face of it it's a wishbone effect with exposed western and especially northern and eastern areas catching most of the frequent snow showers there could be snow inland at times...in any case, it will feel arctic with high windchill and biting Northerly winds with drifting snow and widespread frosts early and late with maxima hardly above freezing and feeling well below zero!..Enjoy:santa-emoji: 

I think the problem is some want the holy grail of over 1 foot of snow ITBY every time. This outlook is so much better than we've been used to and with the chance of snow popping up anywhere. Maybe turning into prolonged snow is great and all this before Christmas. What's also exciting is the chance of sustained cold from the continent after this weekend and in the run up to Christmas

  • Like 4
Link to comment
Share on other sites

Posted
  • Location: Longton, Stoke-on-Trent.
  • Location: Longton, Stoke-on-Trent.
19 minutes ago, Frosty. said:

Those who are expecting most of the uk will miss out on snow later this week and the weekend might get a surprise, with troughs swinging south in the arctic flow that would mean bands of snow showers spreading south so whilst on the face of it it's a wishbone effect with exposed western and especially northern and eastern areas catching most of the frequent snow showers there could be snow inland at times...in any case, it will feel arctic with high windchill and biting Northerly winds with drifting snow and widespread frosts early and late with maxima hardly above freezing and feeling well below zero!..Enjoy:santa-emoji: 

Streamers too. Cheshire Gap streamer in particular. Could push snow showers quite far across the Midlands and perhaps towards the London area.

  • Like 3
Link to comment
Share on other sites

Posted
  • Location: Ely, Cambridgeshire
  • Location: Ely, Cambridgeshire
13 minutes ago, Frosty. said:

Those who are expecting most of the uk will miss out on snow later this week and the weekend might get a surprise, with troughs swinging south in the arctic flow that would mean bands of snow showers spreading south so whilst on the face of it it's a wishbone effect with exposed western and especially northern and eastern areas catching most of the frequent snow showers there could be snow inland at times...in any case, it will feel arctic with high windchill and biting Northerly winds with drifting snow and widespread frosts early and late with maxima hardly above freezing and feeling well below zero!..Enjoy:santa-emoji: 

According to today's charts- the high is gradually getting nudged eastwards, so it contradicts your scenario. Likely the NW'ly flow will maintain but the high will starve off precipitation. On this basis - this weekend at least looks predominantly dry, cold and sunny for all but windward western/northern coasts. Friday looks best for any showers - but the window for widespread showers is narrow and is getting smaller with every run at the moment. 

The jury is still open for next week however - especially if a low can mix with a northerly flow. Low to moderate chance of this at the moment. 

  • Like 3
Link to comment
Share on other sites

Posted
  • Location: Castle Black, the Wall, the North
  • Weather Preferences: Spanish Plumes, Blizzards, Severe Frosts :-)
  • Location: Castle Black, the Wall, the North
13 minutes ago, Matt Ralph said:

According to today's charts- the high is gradually getting nudged eastwards, so it contradicts your scenario. 

It's not really my scenario, it's based on the latest update from Exeter plus my own interpretation of the models so far today..all to play for in my opinion...becoming much, much colder anyway..so I'm happy!:)

  • Like 3
Link to comment
Share on other sites

PLEASE READ THIS POST WITH EXTREME CAUTION!

DISCLAIMER:  I bear absolutely no responsibility for the contents of this post! The analogue charts that I refer to (later on) are purely to look at certain similarities between the current pattern and a "certain" earlier winter. It would be wholly wrong to conclude (or expect) that earlier events might be repeated this winter. This particularly applies to some of the tabloids, to those expecting a severe and snowy winter and some of the less experienced readers on this thread.

As we know, the models have been struggling for a while in first agreeing upon another Arctic re-load and a northerly blast, how potent it will be, its longevity and what follows afterwards. There have been some large swings from one run to the next, even just 4 to 5 days out. Although the northerly (of various descriptions) has now been agreed upon, the detail is still up in the air and very little else has been resolved beyond next weekend and I expect there to be further swings in the model output for much of this week. I will not get into the technical side to this and will leave that up to the experts.

What we have seen during the last month or so is a number of brief northerly outbreaks, roughly a week apart. These have not produced any really significant cold so far although each one has been slightly colder than the previous one, "partly" due to the natural cooling off as we progress into winter. That pattern of MLB in the Atlantic with periods of amplification into the Arctic has produced short lived meridional patterns. The undulating jet stream has meant that the UK has more or less alternated from being on the warm and then the cold side of the jet. For several weeks now we have seen a fairly static pattern with the blocking HP mostly located in the mid Atlantic and LP extending southwards from the Arctic, through Scandinavia and into northern and now central Europe. Here are some of the charts from the last few weeks. They are all ECM 0z runs using the T+0 output to show the actual "current" pattern for the date selected:

            5th November 2017                         13th November 2017                          24th November 2017                      30th November 2017                 4th December 2017 - current

ECH1-0.GIF?00    ECH1-0.GIF?00    ECH1-0.GIF?00   ECH1-0.GIF?00  ECH1-0.GIF 

These all, more or less, show the last four brief northerlies. Now let's look ahead for several charts moving on from the current pattern on last night's ECM 0oz chart (above) and then the rest of the run from T+96 to T+240 and also GFS and GEM for T+240::

ECM:    T+96  December 8th                      T+120  December 9th                       T+144  December 10th                      T+168  December 11th                   T+192  December 12th 

ECH1-96.GIF   ECH1-120.GIF    ECH1-144.GIF    ECH1-168.GIF   ECH1-192.GIF

  ECM  T+216  December 13th          ECM 0z T+240  December 14th           GFS 0z T+240 December 14th         GFS 6z T+234 December 14th       GEM 0z T+240 December 14th

ECH1-216.GIF   ECH1-240.GIF    gfsnh-0-240.png    gfsnh-0-234.png?6?6   gemnh-0-240.png 

The last four charts are for D10, 0100 on December 14th. These all show colder patterns at that time. I fully appreciate that we are moving well into FI and this time period is "after" the likely broader pattern changes expected around T+120 to T+168. The main point here is that whatever route some of the main models take (and some go for a short milder interlude) they generally end up with a colder pattern with renewed amplification into the Arctic. Some runs are cold throughout. Note that UKMO only go up to T+144 and the JMA model only shows yesterday's 12z for this D10 period although it too ends up with another northerly at that time, so these two models are not shown. Several of the recent runs and some of the GEFS and ECM ensembles showing a succession of slider lows running south-east from Greenland  or south of Iceland usually via some part of the UK and then phasing with the Scandinavian/European LP block. These are based on the jet stream taking a north-west to south-east route. If there is sufficient cold air maintained in our vicinity and to our east (and north), then there is potential for snowfall as well as quite severe frosts, especially in any slacker period of pressure in between systems. There might be short-lived less cold interludes as the LPs engage with the mild air to the south. 

Now the interesting and highly speculative bit. I have been racking my brains to think of past winters with similar patterns. Most of our longer lasting cold spells come in from the east such as in December 2010 Sometimes there is an alternation between northerlies and easterlies. At this stage of the winter there are actually very few close analogues. Let's assume that we get lucky and start to see the pattern of successive "sliding" LPs moving across us and with some cold air embedded. At this time of the year, the UK is very capable of building and maintaining its own cold pool, given the right synoptics to initiate it and without the jet stream suddenly switching to a direct west to east or south-west to north-east trajectory and blasting everything away in its path. I have come up with 1962-63!!!!  Again, I should remind everyone that it's very dangerous to use analogues as only minor differences can produce very different outcomes. Back in the '60s the Arctic ice sheet frequently engulfed the north Iceland coast and was over 50% more extensive than it is today. I'll let the experts provide comparisons on the state of the ENSO and other teleconnections for that epic winter.

The 1962-63 winter produced some highly unusual synoptics. The winter started off with a number of brief northerlies during the second half of November and early December very similar to some of those we have seen so far this winter. Then there was a period with HP right over the UK with some cold and very foggy weather during the first week of December (this seems less likely for this December). After another brief northerly, the HP then built into Greenland just before Christmas and the severe spell commenced. There were a number of Arctic top ups and sometimes a proper cut off Greenland HP and there were also long periods of only MLB with little amplification. There were occasional easterlies with short lived Scandinavian HPs but actually hardly any long fetched easterlies. Much of the severe cold was confined to a deep cold pool which developed and stagnated over central and western Europe, including the UK. In fact much of Asia, Russia as well as North America had a pretty average winter! One of the most frequent and repeated patterns were sliding LPs moving east-south-east from the mid Atlantic. Examples of these occurred throughout the 10 week cold spell from Dec 26th onwards. I remember numerous occasions when the forecast was for a short spell of snow followed by much milder weather with a steady thaw. These never materialised and there were various accounts of that winter which suggested that the tracks of these LPs were "against the whole weight of meteorological probability". There were only very occasional and very short lived less cold interludes (mostly confined to the extreme south-west) and many parts of the UK saw long periods with "ice days". Let's have a look at some of the charts which all come from the excellent NCEP Reanalysis Archives on Meteoceil (link: http://www.meteociel.fr/modeles/archives/archives.php?mode=2&month=12&day=30&year=1962&map=4&type=ncep). You can examine the charts and 850s etc for the whole of that winter and move through the charts on a rolling 15 period. The records go all the way back to 1871:

            November 15th 1962                     December 10th 1962                          December 26th 1962                       December 30th 1962                       January 2nd 1963  

archivesnh-1962-11-15-0-0.png  archivesnh-1962-12-10-0-0.png  archivesnh-1963-1-6-12-0.png  archivesnh-1962-12-30-0-0.png  archivesnh-1963-1-2-0-0.png

 

               January 5th 1963                           January 6th 1963                             February 6th 1963                          February 8th 1963                           February 9th 1963  

archivesnh-1963-1-5-0-0.png   archivesnh-1963-1-6-12-0.png  archivesnh-1963-2-6-12-0.png  archivesnh-1963-2-8-0-0.png  archivesnh-1963-2-9-0-0.png

 

             February 15th 1963                         February 17th 1963                           February 24th 1963                    March 5th 1963 - the end!  

 archivesnh-1963-2-15-0-0.png    archivesnh-1963-2-17-0-0.png  archivesnh-1963-2-24-0-0.png  archivesnh-1963-3-5-0-0.png 

I really do feel that readers should consider all this as a "bit of fun" and that "Bring Back 1962-63" permanently lives on Fantasy Island! There is a more serious side though. Despite anywhere near a repeat of the epic '62/63 winter being extremely unlikely, it does show what can happen when the pattern gets stuck in a rut and just very occasionally that rut is with the UK under the coldest part of it all. I will be looking out for these sliding lows and whether the renewed PNA and mid-Atlantic ridges set up with some further bouts of amplification into the Arctic and the jet stream is sometimes set on a north-west to south-east path to sometimes allow LPs to break through and/or very cold air to stagnate over the UK and north-west Europe. If we get that pattern, then its a question of how long it might last.

Now, any advice on how I can "de-ramp" my reputation!

 

Link to comment
Share on other sites

Posted
  • Location: Lytchett Matravers - 301 ft ASL
  • Weather Preferences: Snowy Winters, Torrential Storm Summers
  • Location: Lytchett Matravers - 301 ft ASL

If member 37 were to come to fruition, the Home Counties folk won't be opening the front door of their house, never mind driving to work :cold-emoji:

 

  • Like 1
Link to comment
Share on other sites

Posted
  • Location: Drayton, Portsmouth
  • Location: Drayton, Portsmouth
1 minute ago, karlos1983 said:

If member 37 were to come to fruition, the Home Counties folk won't be opening the front door of their house, never mind driving to work :cold-emoji:

 

Always something for fun on these ensembles!! Hope is a wonderful thing, we need a lot of it on the south coast...

But like I said earlier, the snow envelope is currently very wide for T168 (including a "no snow" envelope, of course)

  • Like 3
Link to comment
Share on other sites

Guest
This topic is now closed to further replies.
  • UK Storm and Severe Convective Forecast

    UK Severe Convective & Storm Forecast - Issued 2024-03-29 07:13:16 Valid: 29/03/2024 0600 - 30/03/2024 0600 THUNDERSTORM WATCH - FRI 29 MARCH 2024 Click here for the full forecast

    Nick F
    Nick F
    Latest weather updates from Netweather

    Difficult travel conditions as the Easter break begins

    Low Nelson is throwing wind and rain at the UK before it impacts mainland Spain at Easter. Wild condtions in the English Channel, and more rain and lightning here on Thursday. Read the full update here

    Netweather forecasts
    Netweather forecasts
    Latest weather updates from Netweather

    UK Storm and Severe Convective Forecast

    UK Severe Convective & Storm Forecast - Issued 2024-03-28 09:16:06 Valid: 28/03/2024 0800 - 29/03/2024 0600 SEVERE THUNDERSTORM WATCH - THURS 28 MARCH 2024 Click here for the full forecast

    Nick F
    Nick F
    Latest weather updates from Netweather
×
×
  • Create New...