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Model output discussion - The run up to Christmas


Met4Cast

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Posted
  • Location: Gillingham, Kent
  • Weather Preferences: Snow, Thunderstorms,
  • Location: Gillingham, Kent
On 20/12/2020 at 20:51, Scott Ingham said:

@Met4Cast These have already changed.

So thats background signals EC Det and Eps the last 9 GFS operationals and GEFS and UKMO vs ?????????

No it isn't. 

A true Greenland high isn't supported by the EPS, GEFS or the background signals, MJO isn't supportive of a Greenland high. The UKMO doesn't even have a Greenland high, in actual fact it's likely the low over Canada would move eastwards cutting the very weak link on the next frame as that's where energy is heading at 144.

THIS.thumb.png.1a80a12609878baa877bef9c12a167e3.png < This isn't supported.

 What IS supported within the EPS & GEFS & UKMO is an Atlantic ridge that temporarily extends up into S Greenland before "toppling" to a N Atlantic ridge. There's no doubting it's going to turn colder, and I agree with you that these things usually shift eastwards as the time-frame nears, indeed we're already seeing the ensemble means further east with the low than the det runs.

The GEM is pretty much bang on with how I think the pattern will evolve.

GEM.thumb.png.d4539a1ca19b4f9891db572de58681e7.png < Brief riding up to S Greenland, a more direct northerly, GEM bang in-line with the GEFS/EPS means.

 

GEM2.thumb.png.de4bc9269096c67a2baeba69261017e7.png < Block unsustained, too much residual vorticity over Canada for the block to build into Greenland. 

What we're left with is a northerly blast, colder than current modelling suggests though likely nothing "exceptional' with a snow risk primarily across N hills, but depending on small bumps in the flow/shortwaves perhaps a more widespread threat, but not worth looking at those sorts of details at this range. 

A period of below average temps xmas > new year with a risk of snow, probably a few surprises given we do see a slightly cooler airflow than currently modelled. I wouldn't be surprised to see the signal for the high to topple over the UK to grow given the signal from GLOSEA favouring HP over the UK into January, GLOSEA did exceptionally well with the call for milder weather during the middle part of this month, was one of the first model to switch to that idea I believe.

On-going strat disruption and hopefully low heights into Europe mean the chances of mild weather are low into Jan, and with a potential SSW early-mid January the rest of winter is all to play for. 

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Posted
  • Location: Dorset
  • Weather Preferences: warehamwx.co.uk
  • Location: Dorset

The Christmas period is approaching fast and something colder could be on the way?! At least, relative to what we have had lately.

Keep it friendly! Use the report button rather than replying to off-topic posts, or posts that could be considered a wind up. The team will try it's best to sort it out.

Merry Christmas!  :santa-emoji:

Slight technical hitch - apologies.
 

If your post is less about model discussion, and more of a ramp/moan or just a general post about the current outlook, please use this thread:

https://www.netweather.tv/forum/topic/94744-winter-202021-moans-ramps-chat/

Learn more about meteorology: 

https://www.netweather.tv/forum/learning/

Model Output And Charts On Netweather:

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GFS
GFS Ensembles
ECMWF
ECMWF EPS
NetWx-SR (3km)
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Model Comparison
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Posted
  • Location: NR Worthing SE Coast
  • Location: NR Worthing SE Coast

Ecm was close to mild outlier regarding the upper air temps,from a week onwards so plenty of upgrades possible in the days ahead.

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Posted
  • Location: Bedfordshire
  • Weather Preferences: Thunderstorms, plumes, snow, severe weather
  • Location: Bedfordshire

Perturbation 7 of the 12z GFS is absolutely bonkers..

- 850 temps around -13/-14c for the whole country (it shows -15c for my location)

- Loads of snow

- Quite tight isobars to the NE of the country, means that blizzards are a possibility if it comes off (like it ever comes off anyway)

- The low gets trapped to our east for at least 5 days

gens-7-1-300.thumb.png.702a0fd068ff89facacb2ceb968775b6.png   gens-7-0-300.thumb.png.82bb9166b0a6cccd6f80e2b78d420049.png   gens-7-1-312.thumb.png.8d16513803a981a7c3100151e4e17d40.png   gens-7-0-312.thumb.png.ea4a62c3e870b60d4c26c58e6fec44e5.png

Edited by Zak M
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Posted
  • Location: Hoyland,barnsley,south yorkshire(134m asl)
  • Weather Preferences: severe storms,snow wind and ice
  • Location: Hoyland,barnsley,south yorkshire(134m asl)

The latest from ICON has more of a NE flow for the SE on Christmas eve evening

18z 96 v's 12z 102

icon-0-96.thumb.png.ef802af740763e3f318a115443972447.pngicon-0-102.thumb.png.b67a663e221e960d3c10d6b4c2857af4.pngicon-2-96.thumb.png.90d785735ca82c07626d0ce29fe2fd0a.png

this could enhance the shower activity in said location.

 

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Posted
  • Location: Manchester Deansgate.
  • Weather Preferences: Heavy disruptive snowfall.
  • Location: Manchester Deansgate.
Just now, Scott Ingham said:

Great to see the EPS on board with a prolongment of the cold weather.

Just taken a look at the strat. WOW!!!

A split down to -25ms

WOW - not on the EPS mean surely???

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Posted
  • Location: Cambridge
  • Weather Preferences: Cold, snow, heat, sunshine and thunderstorms. Anything severe.
  • Location: Cambridge
3 minutes ago, Zak M said:

Perturbation 7 of the 12z GFS is absolutely bonkers..

- 850 temps around -13/-14c for the whole country (it shows -15c for my location)

- Loads of snow

- Quite tight isobars to the NE of the country, means that blizzards are a possibility if it comes off (like it ever comes off anyway)

- The low gets trapped to our east for at least 5 days

gens-7-1-300.thumb.png.702a0fd068ff89facacb2ceb968775b6.png   gens-7-0-300.thumb.png.82bb9166b0a6cccd6f80e2b78d420049.png   gens-7-1-312.thumb.png.8d16513803a981a7c3100151e4e17d40.png   gens-7-0-312.thumb.png.ea4a62c3e870b60d4c26c58e6fec44e5.png

Poor effort, the -24C uppers don’t even make it.

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Posted
  • Location: sheffield
  • Weather Preferences: cold ,snow
  • Location: sheffield
1 minute ago, Scott Ingham said:

Great to see the EPS on board with a prolongment of the cold weather.

Just taken a look at the strat. WOW!!!

A split down to -25ms

Yes just taken a look, sounds very positive on the strat thread. Hopefully transfers into a favourable outcome in the new year on our nhp

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Posted
  • Location: Rotherham, East Dene
  • Location: Rotherham, East Dene
3 minutes ago, feb1991blizzard said:

WOW - not on the EPS mean surely???

Sorry mate i didnt make that clear enough. No this was on the GFS 12z. Very impressive all the same. There is nothing left of the vortex when it was done 

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Posted
  • Location: Gillingham, Kent
  • Weather Preferences: Snow, Thunderstorms,
  • Location: Gillingham, Kent

A true Greenland high isn't supported by the EPS, GEFS or the background signals, MJO isn't supportive of a Greenland high. The UKMO doesn't even have a Greenland high, in actual fact it's likely the low over Canada would move eastwards cutting the very weak link on the next frame as that's where energy is heading at 144.

 THIS.thumb.png.24697fa14bd840a3933824a63910a1de.png< This isn't supported.

 What IS supported within the EPS & GEFS & UKMO is an Atlantic ridge that temporarily extends up into S Greenland before "toppling" to a N Atlantic ridge. There's no doubting it's going to turn colder, and I agree with you that these things usually shift eastwards as the time-frame nears, indeed we're already seeing the ensemble means further east with the low than the det runs.

The GEM is pretty much bang on with how I think the pattern will evolve.

GEM.thumb.png.c04409164d86fc31eca2970ca1e0941f.png < Brief riding up to S Greenland, a more direct northerly, GEM bang in-line with the GEFS/EPS means.

 GEM2.thumb.png.476c9619e186c83fa43ba4beecc57fff.png< Block unsustained, too much residual vorticity over Canada for the block to build into Greenland. 

What we're left with is a northerly blast, colder than current modelling suggests though likely nothing "exceptional' with a snow risk primarily across N hills, but depending on small bumps in the flow/shortwaves perhaps a more widespread threat, but not worth looking at those sorts of details at this range. 

A period of below average temps xmas > new year with a risk of snow, probably a few surprises given we do see a slightly cooler airflow than currently modelled. I wouldn't be surprised to see the signal for the high to topple over the UK to grow given the signal from GLOSEA favouring HP over the UK into January, GLOSEA did exceptionally well with the call for milder weather during the middle part of this month, was one of the first model to switch to that idea I believe.

On-going strat disruption and hopefully low heights into Europe mean the chances of mild weather are low into Jan, and with a potential SSW early-mid January the rest of winter is all to play for. 

(Not sure what going on with the forum, but for some reason my post is at the top of the page in red? I assume that'll be removed because I'm not a king, so I'll repost it)

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Posted
  • Location: Hoyland,barnsley,south yorkshire(134m asl)
  • Weather Preferences: severe storms,snow wind and ice
  • Location: Hoyland,barnsley,south yorkshire(134m asl)
8 minutes ago, sheikhy said:

Icon more amplified at 114 hours around eastern usa!!

Yes,more positives going forward ☺️

the 18z at 120 v's 12z 126.

iconnh-0-120.thumb.png.f49e97925960677f035140efb0b516cb.pngiconnh-0-126.thumb.png.9d41480074a00f3f95d5f932ce558fbc.png

Edit:,just to add,there is more lower height's around the Azores propping that ridge up more.

Edited by Allseasons-si
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Posted
  • Location: Rotherham, East Dene
  • Location: Rotherham, East Dene
7 minutes ago, swfc said:

Yes just taken a look, sounds very positive on the strat thread. Hopefully transfers into a favourable outcome in the new year on our nhp

Fingers crossed mate. This so far has been an outstanding start to winter 

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Posted
  • Location: Manchester Deansgate.
  • Weather Preferences: Heavy disruptive snowfall.
  • Location: Manchester Deansgate.
3 minutes ago, Scott Ingham said:

Sorry mate i didnt make that clear enough. No this was on the GFS 12z. Very impressive all the same. There is nothing left of the vortex when it was done 

Nearly had an or------ when i saw that, yes, i was starting to worry as GFS ops had been less pronounced splits lately until that, if i was hyper critical though, right up top its a massive wide split with a stonking big ridge over the pole, but one of the daughter vortices ends up guess where??  -  yes, the Atlantic!

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Posted
  • Location: Gillingham, Kent
  • Weather Preferences: Snow, Thunderstorms,
  • Location: Gillingham, Kent
8 minutes ago, Scott Ingham said:

No mean is going to show a true Greenland height and I suggest you view the latest eps its almost as good as it gets. 

If your going to call a ridge with yellow heights only go a third up Greenland and not call it a Greenland high you do that but its very clever wording and its pointless.

Enjoy the current modelling and end the I am right you are wrong thing you have going on 

All the modelling today has strengthened the signal and your calling not a lot of cold or snow before we even get within 72 hours

That isn't a Greenland high, it's a ridge up into Greenland. That is VERY different. The GFS shows a Greenland high. The ensembles however do not support that. I've also not said anyone is right or wrong, simply giving my view. Heck, I even said I agree with you lmfao.

I also made it pretty clear in my post that it looks likely to be cold, and in fact, said it was likely to be colder than current modelling suggests, so your last sentence doesn't make any sense whatoever. 

Edited by Met4Cast
Unnecessary comment removed
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Posted
  • Location: Leicester
  • Location: Leicester
5 minutes ago, Met4Cast said:

That isn't a Greenland high, it's a ridge up into Greenland. That is VERY different. The GFS shows a Greenland high. The ensembles however do not support that. I've also not said anyone is right or wrong, simply giving my view.

18z could back up what your saying!!lets see?

Edited by Blessed Weather
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Posted
  • Location: Wantage, Oxon
  • Weather Preferences: Hot, cold!
  • Location: Wantage, Oxon

So, new thread, where are we right now?  

If there was a 3 phase process we have to go through to get decent snowy cold spell nowadays it is something like this:

  1. Get a decent high latitude blocking scenario.  This box is now ticked. Cross model agreement on a ridge towards or into Greenland, or even a Greenland high.  
  2. Get the cold air in place.  Warm SSTs to our north and east and lack of really cold air in our bit of the NH overall so far this December are a temporary issue here, but in the heart of winter, this should change quickly.
  3. Precipitation.  When it comes, will it be snow, need to leave this to within 2 days, or nowcasting, frankly!  

We now move to phase 2.  

But looking a bit further ahead, what of our prospects of a really special cold spell?  

As I alluded to earlier when discussing the ECM, where is any spoiler weather going to come from upstream?  ECM and GFS at T240:

1C730A41-E03B-479B-BD71-FB09F42DB0B3.thumb.jpeg.745eb8d477f39c34aea0f5183a01ca18.jpegEFF514F7-FB8D-4057-BD41-9D9B64E3D6DA.thumb.jpeg.1418472443b4065ef48100dcb2f94755.jpeg

Anything threatening west/left/upstream of the black squiggle?  No.  A pattern favourable for cold could have some longevity.  But...

A SSW could throw everything in the air, so if we are to have one (and we can’t complain - it is all part of the pattern) it needs to land right, it would be double or quits in my view!  GFS 12z at T384 completely mashes the strat vortex:

39F568B2-8A37-4D7E-BDA8-869612D3A1C9.thumb.png.834be018c9eab410f964aa486d0085e1.png

What effect will this have on the weather in the trop that affects us a few weeks down the line?  That is phase 4, and we have no idea of the answer as yet!

All the best, Mike

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Posted
  • Location: Bury St Edmunds, Suffolk
  • Weather Preferences: Cold, frost and snow
  • Location: Bury St Edmunds, Suffolk

Great overall pattern across all models tonight, although I'd have to say the GEM is my favourite.

The GEM gets that trough just far enough east of us to bring the coldest air down over us.

The other models are currently just a bit too far west, meaning the coldest of air ends up going into the Atlantic.

Plenty of time for corrections east as yet, but more importantly let's get these ridges into Greenland nailed first. 

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Posted
  • Location: Scouthead Oldham 295mASL
  • Location: Scouthead Oldham 295mASL

Anyway....

Let's get the colder air in then worry about uppers etc...

Small changes at short lead times can have a big bearing on surface conditions.. 

The trend through today has been good, there is no doubt if we don't see a cut off Gteeny high then things will sink ,the hope is troughing is well established to the south by months ends...

 

 

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Posted
  • Location: st albans
  • Location: st albans

Further to the chat about where the trough might end up, note that the latest eps run retrogresses the Russian ridge back towards a nw Russian  locale .........that may mean the sceuro trough can’t push further east 

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