Model Output Discussion 01/09/17

[tight isobar]

Gfs 18z...

All roads point to cold..

Likely v-notable too.

Some quite amazing stuff today..

And everything appears to be dropping at just the correct times/locations....

[chionomaniac]

I remember 09/10 when we saw any mild progression in the longer term output keep getting pushed back as we are used to with cold in FI. I suspect that we will see a repeat of this as the trop disrupts the strat and then this rebounds back to the trop. I think that a traditional La nIna pattern will eventually win out, but I am not expecting that any time soon. Hopefully the synoptic upcoming pattern will be cold enough to drag cold enough 850's to produce snow - even as far south as my location. A tall order I know!

[Dennis]

[Allseasons-Si]

1 minute ago, northwestsnow said:

Yes- that cold pool over scandy did lead to heights building- some very cold uppers now situated inPoland/Germany/into France- its actually a cracking run in that the block moves to settle over Scandy and thats good news for coldies 

Yes,just across the channel and developing a cold pool and slowly heading this way

[northwestsnow]

First week of December on GFS 18z looks cold , cold and more cold, so happy to see this block stay to our north- snapshot of next week- scotland looks absolutely bitter..

[northwestsnow]

Are we going to see a northerly ?

[Ice Day]

Just now, northwestsnow said:

Are we going to see a northerly ?

Why not, we've seen everything else!  A truly excellent run, the 0c Isotherm doesn't leave the UK for pretty much the entirety of the run out to 312.  

[karlos1983]

 

1 minute ago, northwestsnow said:

Are we going to see a northerly ?

Looks that way! Nws 

This cold spell is gaining momentum now, surprises will definitely pop up, I’m convinced the uppers will be colder than currently forecast. What a way to start Winter proper. 

[Allseasons-Si]

6 minutes ago, northwestsnow said:

Are we going to see a northerly ?

There has been some hints of retrogression by some models to park the hp cell back in the atlantic,thanks to the Siberian block.

the gfs looks to be heading that way

Edited November 24, 2017 by Allseasons-si

[nick sussex]

The GFS 18hrs run was very close to being very good but some shortwave energy popped up to the nw to force the high a bit too far south.

If people thought the issues over the shortwave to the nw which heads se this weekend were nervewracking wait for this next drama to start because you'll need the loop back in the jet towards the Low Countries to  deliver the easterly with tonights GFS if this is to be the new trend!

Code Red initiated!

 

 

[Optimus Prime]

5 minutes ago, northwestsnow said:

First week of December on GFS 18z looks cold , cold and more cold, so happy to see this block stay to our north- snapshot of next week- scotland looks absolutely bitter..

Not trying to be too fastidious, is that really all that notable for a cold spell in early December? The synopsis does appear unusual for the time of year but I'm not sure the temperatures are, given the direction of the wind? Looks slightly underwhelming to me at the moment.

Clearly a very intriguing pattern emerging though. Very similar to Nov/Dec 2010; obviously the cold comparatively being night and day.

[karlos1983]

2 minutes ago, nick sussex said:

The GFS 18hrs run was very close to being very good but some shortwave energy popped up to the nw to force the high a bit too far south.

If people thought the issues over the shortwave to the nw which heads se this weekend were nervewracking wait for this next drama to start because you'll need the loop back in the jet towards the Low Countries to  deliver the easterly with tonights GFS if this is to be the new trend!

Code Red initiated!

 

 

Easterlies nick!! Never straight forward, not sure I’ve got the nerves for that these days.  Never ending dramas. Probably easier to cross the Atlantic in a canoe

Edited November 24, 2017 by karlos1983

[northwestsnow]

1 minute ago, Optimus Prime said:

Not trying to be too fastidious, is that really all that notable for a cold spell in early December? The synopsis does appear unusual for the time of year but I'm not sure the temperatures are, given the direction of the wind? Looks slightly underwhelming to me at the moment.

Clearly a very intriguing pattern emerging though. Very similar to Nov/Dec 2010; obviously the cold comparatively being night and day.

No its certainly not notable but after the horrors of the last few early Decembers i think its great- i would imagine its a couple of degrees below the norm.

[Derecho]

GFS produces a stonking pub run and as others have mentioned the surface cold will be building with the slack winds. Then the ridging to Scandi keeps warmer air at bay before a northerly later on!

There are many positives from this run:

- The major plume of warm air heading to Greenland could have knock on effects later, ie reinforcing any northern blocking later on
- The fact that 850s prior to next weeks forecast northerly keep nudging downwards to our north
- Potential for a rise in SLP over Scandanavia
- Drop in temperature over the nearby continent.

Still feeling a bit cautious due to the UKMO so I don't want to get my hopes up...but if the 18z transpired I would be more then happy. The most important thing is to get everything out to T120 nailed down and send that warm air upto Greenland and build that high. Once that is achieved things could get really interesting but lets wait and see, fingers crossed
 

Edited November 24, 2017 by Quicksilver1989

[cheeky_monkey]

polar vortex gets completely wiped out across northern and eastern Canada towards the end of the run..which is where it normally resides over winter.

[nick sussex]

1 minute ago, karlos1983 said:

Easterlies nick!! Never straight forward, not sure I’ve got the nerves for that these days. 

I've filled up the drinks bar in readiness!

The ridge topple would be less stressful if the high was sufficiently north, the loop back in the jet way holds many bitter memories!

[Summerstorm]

Be careful not to drool over your keyboards guys  

[Frosty.]

4 minutes ago, nick sussex said:

Code Red initiated!

 

 

I'm waiting for code white

Really great 18z with colder uppers (T850's)...Fingers crossed the momentum continues for a NATIONWIDE real taste of winter next week onwards.

[Optimus Prime]

8 minutes ago, northwestsnow said:

No its certainly not notable but after the horrors of the last few early Decembers i think its great- i would imagine its a couple of degrees below the norm.

Ah right, ok:

Well the first 7 days of December 2015 averaged 10.7c (for England). That will not be repeated this year.

 

Edited November 24, 2017 by Optimus Prime
For England

[Geordiesnow]

A northerly of some sorts will definately happen now next week, the questions will be just how far eastwards will the centre of the low that travels over the UK on Monday will head and how long will the cold Northerly flow will occur. Ideally you don't want the low to stall too close to the east coast as any over hanging cloud and rain from any weather fronts will kill convection and it also means the cold air will struggle to head southwards down eastern areas.

2nd thing will the high topple in quickly or slowly, history may suggest the former but if we do get a decent link up like the GFS and the ECM is showing then the Northerly flow will last longer and in general the high will remain out to the west, possibly start to get closer to the UK at times but the UK most certainly remain on the cold side with a chilly northerly flow continuing.

I would not rule out the UKMO occuring because if the link up gets broken, then the high will start to sink towards us but even if that occurs, theres a possibility we may still stay on the cold side and if its ridges in quite quickly then fog and frost will occur which is not bad for this time of year Don't really want a half way set up like this morning's ECM FI charts where some milder air starts to topple in around the flow as that mean more general cloudier conditions but at this stage details are very hard to predict and its just going to be interesting model viewing on how this will play out.

[Gael_Force]

9 hours ago, Man With Beard said:

I think the brunnur.vedur.is site is probably safe to post from because I would imagine it is owned by the Icelandic Met Office so they must have paid ECMWF for specific rights to reproduce charts relating to Iceland (which fortunately just about covers the UK in some instances)

The following is the translation of the header on the site ... seems to be saying it is there for the public and others to use. 

Quote

About this site you can access various data provided by the Icelandic Meteorological Office. The purpose of this site is to provide access to this data to the public, companies and organizations, - this site is not conceived as a traditional website, with a lot of work being done in user friendly presentation and indexing of data. If you are interested in such sites, please visit the web site of the Icelandic Meteorological Office, or the web site of the parties using this data.

 

[nick sussex]

Heres an example of the infamous jet loop which delivered a short but sharp very cold easterly flow: Dec 26 2005:

12 hours later:

Whats interesting about these charts is how even though you've got a mean looking PV to the north west you can still beat those odds and get cold. Although in recent winters that's been much harder.

These jet loop easterlies  normally happen when you have ridge over or near the UK at the outset and then you get lucky with the evolution.

This was the chart a day earlier:

Edited November 24, 2017 by nick sussex

[Man With Beard]

EC 12Z clusters: 2 out of 3 clusters want to build/maintain/rebuild a Greenland High between D11-D15

Incidentally, at D8-D10, the ECM op run was halfway between flatter and more amplified options.

[bobbydog]

based on current model output, background signals and other factors put forward by some of our respected members, i would put a little bet on some imminent wintry weather, then a seemingly 'disappointing' interlude mid-month, then a once in a lifetime winter to rival '62-'63, beginning around the 6th-7th january....

i may be wrong - but i'm putting snow tyres on my christmas list....

Edited November 24, 2017 by bobbydog

[bluearmy]

12 minutes ago, Man With Beard said:

EC 12Z clusters: 2 out of 3 clusters want to build/maintain/rebuild a Greenland High between D11-D15

Incidentally, at D8-D10, the ECM op run was halfway between flatter and more amplified options.

As does the GEFS 18z - starting to think this third push of cold will be the one that might bring the snowfall .............