Model Output Discussion - 30th November onwards

[TEITS]

 

In Summary the weather is set to turn colder briefly at the end of this week and next weekend with some snow possible for a time in the North and East and sharp overnight frosts in the cold North wind. In the meantime the weather will stay cloudy and benign with dry weather until a couple of weak fronts deliver the cold snap soon after midweek. Then through Week 2 it's all about where the High killing off the cold North feed ends up. The Americans seem to want to sink it SE over Europe quite quickly next week setting up a changeable and relatively mild and breezy SW feed with rain at times, mostly in the North and West while ECM shows High pressure holding across the South with a return to benign and increasingly cloudy and less cold conditions following a frosty start to the week. Which is right? It's a case of more runs needed I'm afraid.

 

 

 

If you don't mind me saying Gibby I would change the summary to saying North and West for the snowfall. The reason I say is the models suggest a W,ly element to the N,ly so places such as NW Wales are more prone to snowfall. The only exception is possibly parts of N/E Norfolk as geographically this location is exposed to a NW,ly also.

 

The further outlook remains unchanged in my opinion with HP in charge providing settled, dry conditions with frost, fog a risk at night. A very slim chance of an E,ly developing later. Shall post more on this later on.

[bluearmy]

If there can be north sea storm surges there can be polar lows, depends how the strengthening arctic flow is aligned and how long it lasts, we know that showery troughs will swing south from the arctic because the fax chart on a previous page shows them..wait and see... :-)

Karl, true polar lows can only form under specific circumstances re upper air temps at 500 hpa (I could be wrong on that). I suspect that iceberg has done his homwework before making such a statement but uppers are certainly looking very low to our north. I wonder if the flow will be long fetch for long enough to allow one to form and hit the uk?

[radiohead]

I could live to regret this, but there is No chance of  Polar Low under this set up. You don't have the fetch with the correct 500 temps and the 500 winds are not the correct angles.I just want peeps to be realistic.

I agree, the eastward shift on the last two ECM runs has removed the risk of a polar low. It was probably showing up on a few ENS members that were showing a straighter flow, not shunted as far east. That looks very unlikely now.

[Iceberg]

I think Ian mentioned a few ECM ens members bring one down from just off the Norwegian coast. Of course, if it happens we get into the definition of the differences between a true polar low and a small depression coming down from arctic.

 

Yes BA, I saw Ian post yesterday and tbh i think he got his terminology wrong as we now Polar lows just dont show up in global models 5+ out. Also none of the models show an NE air stream that could possibly carry anything from Norway to our shores. Its either north or west of north.

I also disagree with Gibby's comment that the east will get showers, their just isn't really anything to suggest that will happen in the models.

Not making my self very popular here and happy for anybody to post up charts etc disagreeing with this. Sorry, feel like a real party pooper. !  

[bluearmy]

If you don't mind me saying Gibby I would change the summary to saying North and West for the snowfall. The reason I say is the models suggest a W,ly element to the N,ly so places such as NW Wales are more prone to snowfall. The only exception is possibly parts of N/E Norfolk as geographically this location is exposed to a NW,ly also. The further outlook remains unchanged in my opinion with HP in charge providing settled, dry conditions with frost, fog a risk at night. A very slim chance of an E,ly developing later. Shall post more on this later on.

Good to have you back dave. appreciate it's been tough. This thread needs posters with some insight.

[Cloud 10]

Anyone looking at the UKMO this morning who remembers the debate about yesterdays 12Z will be intrigued to see that the UKMO has dropped the idea of the 75% of energy over the top. We now have a more uprighted  Atlantic trough and deeper cold down the UK as a result. 

 

UN120-21.GIF

 

UN144-21.GIF

 

The change in the UKMO is even more marked when comparing yesterday's 00z run with today's.

 

yesterday..  today..

 

 

The ECM is very similar to yesterday when doing the same comparison but with a stronger link between the Atlantic and Greenland high's.

 

yesterday..  today..

 

 

The GFS basically hasn't turned up yet!

[bluearmy]

Yes BA, I saw Ian post yesterday and tbh i think he got his terminology wrong as we now Polar lows just dont show up in global models 5+ out. Also none of the models show an NE air stream that could possibly carry anything from Norway to our shores. Its either north or west of north.I also disagree with Gibby's comment that the east will get showers, their just isn't really anything to suggest that will happen in the models.Not making my self very popular here and happy for anybody to post up charts etc disagreeing with this. Sorry, feel like a real party pooper. !  

I wonder if ECM op now working at 137 levels/16km is a high enough resolution to model polar low formation several days out ice?

[Man With Beard]

Yes BA, I saw Ian post yesterday and tbh i think he got his terminology wrong as we now Polar lows just dont show up in global models 5+ out. Also none of the models show an NE air stream that could possibly carry anything from Norway to our shores. Its either north or west of north.I also disagree with Gibby's comment that the east will get showers, their just isn't really anything to suggest that will happen in the models.Not making my self very popular here and happy for anybody to post up charts etc disagreeing with this. Sorry, feel like a real party pooper. !  

In these situations I think it's pot luck as to whether most inland areas get snow, features can spring up with northerlies with 48 hours notice but doesn't always happen

[Iceberg]

BA. I just can't see it tbh, they might be able to pick up on short wave features or surface lows, maybe just about possible, but it would be so uncertain as to be ignorable.

For anybody interested in Polar lows, theres a book about them here.

Unstable air flow, straight fetch (normally 24 hrs) and -45C mi trop. Although they have occured at -40 as it think this varies with the sea temp.

A favoured place seems to be the arctic air coming long and straight over the gulf stream waters to the north of scotland, pretty good combination as many scots will know.

 

http://books.google.co.uk/books?id=-tBa1DWYoDIC&pg=PA227&dq=cold+core+low+book&redir_esc=y#v=onepage&q=cold%20core%20low%20book&f=false

[tinybill]

In these situations I think it's pot luck as to whether most inland areas get snow, features can spring up with northerlies with 48 hours notice but doesn't always happen

http://www.meteociel.fr/modeles/gfse_cartes.php?mode=2&ech=6

 

not  to me  to say any thing but it showing poss  snow  for the east coast from  120hr to  150 hr  at the moment  so gibby could  be  right!

[lawrenk]

If you don't mind me saying Gibby I would change the summary to saying North and West for the snowfall. The reason I say is the models suggest a W,ly element to the N,ly so places such as NW Wales are more prone to snowfall. The only exception is possibly parts of N/E Norfolk as geographically this location is exposed to a NW,ly also. The further outlook remains unchanged in my opinion with HP in charge providing settled, dry conditions with frost, fog a risk at night. A very slim chance of an E,ly developing later. Shall post more on this later on.

Not mod related but nice to see you back TEITS.

[IDO]

GFS spreads still show the ens have not resolved the low exiting from the east conus, at T144:

The two areas of higher spread are that Low and the UK, as to where the trough falls; as others have said a causal relationship.

At T240 the spread moves to:

As the individual ens members show, some go with the high moving east and others try and build it NE/N.

A 2-3 cold spell showing on all models as the likely scenario now. No confidence where the collapsed HP then moves. FWIW only 4 ens members showing zonal in FI (T384).

[Frosty.]

Expect aberdeenshire to be blitzed by heavy snow showers by thursday and then to counties bordering the north sea further south soon after, I wonder if the north sea flooding storm surge risk is still valid?

[SMU]

Morning all-

UKMO the model of choice this morning - just slightly ahead of the ECM with a better split in the flow upstream to start thinking about those scandi heights,

The ECM at 240 is nearly there and the 268 would get that vortex wedge back close to the uk.

Its quiet in here this morning considering the UKMO has jumped off the ship to ECM and well the GFS is still flapping about .....

Can anyone point me in the direction of the raging zonality smiley i think it may have been deleted ....

[nick sussex]

Now that the models are moving towards agreement on a northerly I think of more interest is what happens after that.

Still uncertainty re how far south the high will topple and then is it helped ne again by troughing in the mid Atlantic.

Those easterly hints just won't go away especially with the trend of the ECM past 168hrs.

I should add regarding northerly topplers, even though this is a short northerly its not really a toppler because normally that sinks with a sw flow moving in and the PV moving back into its favourite location ,I'd call this a semi-toppler with easterly potential or STEP for short!

Edited December 1, 2013 by nick sussex

[Barking_Mad]

What ground temps are we looking at across the UK?

[IDO]

Those easterly hints just won't go away especially with the trend of the ECM past 168hrs.

The Control for the ECM 0z in Midden, Netherlands, supports that continental flow:Wind direction: Temps:

[SMU]

Good post nick -

Looking at the reading ensembles 00z the control run stays colder at day 9 than the op ( reading around 3c)

So looking forward to the ECM ens extended - as it could show a brief increase before dropping away if the vortex segment comes back west.

I dont expect the ecm mean at day 10 to be perfect but im sure a few question marks will show in its 240 chart with a question mark around the atlantic returning....

S

Ps great timing im dreaming

Edited December 1, 2013 by Steve Murr

[yorkieblade]

If you don't mind me saying Gibby I would change the summary to saying North and West for the snowfall. The reason I say is the models suggest a W,ly element to the N,ly so places such as NW Wales are more prone to snowfall. The only exception is possibly parts of N/E Norfolk as geographically this location is exposed to a NW,ly also. The further outlook remains unchanged in my opinion with HP in charge providing settled, dry conditions with frost, fog a risk at night. A very slim chance of an E,ly developing later. Shall post more on this later on.

I'm sure I echo everyone's thoughts, great to see you back, we have all missed your very knowledgable posts

[SMU]

Im dreaming what are the angles of degrees on that chart related to wind -

Cheers

S

[Jason M]

Just to add to the previous posts, GEFS this morning are still dropping a few easterly hints of there own deep into FI.

A lengthy period of dry south / south easterlies looks the most likely outcome but we could still snatch victory from the jaws of defeat.

[Ian Brown]

Well there is at least better agreement on the end of the week as you would expect as it moves to 4/5 day timeframe, a short northerly blast with snow showers for Scotland and the NE.

 

Beyond that it isn't a typical toppler but talk of a Scandi High, or at least a Scandi High that can influence the UK is very fanciful with so much energy in the Northern arm. 

[Cecil Hogmanay Melchett]

Interesting developments post Northerly but im not sure the models have the correct setup with the Northerly yet.

The stronger the flow(tighter isobars the better).

From an IMBY point of view its gone a bit pairshaped over the last 24 hours with more of N/NNWy which maywell leave the spine of the UK mainly dry.

All depends on troughts etc in the flow i guess...

[nick sussex]

Im dreaming what are the angles of degrees on that chart related to wind -CheersS

45 northeasterly 90 easterly and so on. Was it a rough night?lolThe penny just dropped Steve, I get the inference now,I think i'm in need of a large coffee! Edited December 1, 2013 by nick sussex

[snowmadchrisuk]

On the first day of winter , ECM gave to me .,...... Just viewed it was like wow , it didn't back down and the UKMO has come towards it .... as for the GFS it's all over the place again , although I don't know why but I have never been a fan of the GFS at the weekend it always seems to be different by Monday morning .... 

 

Them NE Height;s will keep interest after the Northerly for sure.... Snow showers down to lower levels further South than Northern England have to be in the MetOffice's mind this morning now surely.