Model output discussion 25th Jan - The final third of winter beckons..

[Rob Walker]

2 hours ago, Argyle1980 said:

The UK jet stream! Certainly looking like the Atlantic it losing the fight here. Amazing charts .

Yeah seeing that too....

[Guest]

MAINTAINING THE COLD POOL TO OUR EAST

The models are now starting to factor in the impacts of the multiple warmings in the stratosphere with a propagation through the troposphere to the surface. There are timing issues and still questions regarding the details in terms of the extent of the disruption to the PV and where it moves to and sets up camp. This will unfold over the next few days. Most of the recent model output is favouring an evolution towards HLB with HP across Scandinavia ridging westwards or north-westwards to Svalbard around D10 to D15. This would bring renewed deep cold air southwards across western Russia and eastern Scandinavia. With the synoptic pattern favouring LP to the south of the UK and into the Mediterranean, the cold pool could be advected westwards through Europe and into the UK. All the coldies on this forum have their fingers crossed that this is the type of scenario that verifies.

There has been some concern over just how cold it might get, especially in terms of snow potential. As some have said, you do not need particularly low 850s when the surface cold (and the layer just above it) is below freezing. Of course low 850s would be best. Some of the models start to show HP building into Scandinavia as early as D6 but do not (that early on) show particularly cold conditions. This takes me back to my recent obsession with the European cold block!  I still believe that the persistence and strength of this is being completely underestimated by the models and the block might hugely assist in bringing the cold into the UK. The models indicated that the cold pool and the HP would be pushed much further east. While it was shifted eastwards out of western Europe, it is still holding on and the cold pool has hardly lost any of its intensity. I now demonstrate this.

The two "live" charts below are usually updated at regular intervals (at every 10 minutes). When comparing temperatures, you should take account of the time of the day and the natural min/max variations.

European Surface Temperature Charts:

                             Current "live"                                                                 Jan 31st 0650                                                                Jan 30th 0650                                                              Jan 29th 0650

                                                                                    

Note how the cold was pushed out of the UK and western Europe by January 30th but it has come to a standstill since then. See how much the cold has intensified over Scandinavia.   

European Surface Pressure Charts:

                           Current "live"                                                                 Jan 31st 0650                                                                Jan 30th 0650                                                               Jan 29th 0650

                                                                                     

Note that the HP has only weakened very slightly but has maintained its position just north of the Black Sea. Also note a ridge developing towards Scandinavia.

Comment:

It is my belief that the cold pool will be maintained much closer to us than has been predicted. Even if we see several much deeper Atlantic LPs move into the UK around this weekend or early next week, it looks that they will grind to a halt over the North Sea and then be deflected northwards by the block (or better still, perhaps even an earlier undercut than predicted!). Whether or not the persistence of the cold block "accelerates" the evolution towards an "easterly" is not the most important point. The main thing is that the extensive cold pool will not be too far away. Then, when (or if) the deep cold moves down into western Russia and eastern Europe, it will top up the cold pool as it pushes westwards. Even if we do not get the full impacts of the SSW, a Scandinavian HP will still bring in some pretty potent cold conditions.

EDIT:  Judah Cohen's latest Arctic Oscillation Report was published late last night. I no longer provide my full coverage on this but here's the link:

http://www.aer.com/science-research/climate-weather/arctic-oscillation

 

Edited January 31, 2017 by Guest
Add link to Judah Cohen's latest AER

[Stu_London]

Another GFS run where the Operational is very much on the cold side of the ensembles.

Not unheard of the operational to lead the way in these scenarios. I seem to recall in the run up to December 2010 we had a series of outputs where the operational was cold and the ensembles caught up later.

Perhaps it's resolution or quality of data.

 

[Turnedoutniceagain]

[Summer Sun]

[stodge]

Morning all

As the song goes, "what a difference a day makes".

After some uninspiring charts yesterday morning, this morning has brought a notable increase in interest from fans of cold with more than one hinting at some kind of pattern change next week.

I genuinely thought we would need this week AND next week before we saw a significant move but we see this as early as next Monday from the "gold standard" UKMO:

It's hard not to think something might be happening as early as then.

Other models are more cautious on the timing - ECM is the fly in the ointment. The first attempt to build the HP west from Russia fails and sinks south and it's the second attempt that is on the T+240 chart:

The lack of lower heights over Europe is the big worry here and unless the LP dives SE it's hard to see how this develops favourably.

GEM will no doubt have its admirers this morning:

Basically, the Eurasian HP pushes the Atlantic back west and causes disruption to the south thus further supporting the HP. It's a dream chart for cold and snow fans.

GFS 00Z OP at the same time:

GFS is up to its usual trick of taking a lot of energy north compared to the GEM - if that northern energy wasn't there it would be very close to the GEM.

As for the GEFS this morning, the vast majority keep higher heights to the East - the differences are over the strength of the Atlantic and whether the core HP block sinks south (like ECM) or stays over Scandinavia (as per the Op).

Very early days yet - a definite three steps forward for those looking for cold and a step and a half for those looking for snow but very far from a done deal as we all know.

A fascinating 3-5 days of model watching ahead - it does seem the displacement and weakening of the PV is having an effect and the further displacement of that weakened vortex over Canada opens the door for the Siberian/Arctic HP to come westward with the potential advection of some very cold air but to stress once again, nothing is certain, nothing is definite and if experience tells us anything, if there's a way for Britain to miss out on snow, we'll find it. As for cold, I'd be more optimistic of a glancing blow for the SE at the very least from the westward moving cold pool.

As ever, more runs are needed, plenty of time for nerves to fray. There will be significant upgrades and downgrades to come.

[Nick F]

5 minutes ago, Summer Sun said:

Be nice if people could comment as well on the tweets they post!

Anyway, will have to see if there is growing support from the ENS for cold, as the cold members still more in the minority camp for now which suggests uncertainty over whether we can get the block to retrograde to get the UK in on the cold air developing to the east. For now, all we have is a stalemate playing out over the UK between Atlantic trough and block to the east, with UK more under trough influence, but perhaps easing with time.

Edited January 31, 2017 by Nick F

[Stravaiger]

29 minutes ago, Turnedoutniceagain said:

The reason I like this GEM chart so much is that the low to the W of Iberia shuts the door to any meddling heights from the Azores high ridging into Europe and keeping the freezer door shut for the far west of Europe. I am concerned though, that given the Azores high's propensity to ridge into Iberia/France all winter that the ECM's solution might be closer to the money and the Scandi high will eventually sink a bit further south than we want if it is snow we are after.

Really hope I am wrong.

[northwestsnow]

2 minutes ago, Summer Sun said:

Aye, despite the positive developments in the strat its still looking like the mother of all battles to get any meaningful cold to blighty...

gem is the pick of the models this morning and ukmo is better at 144 than ecm but even on ukmo we can see that pain in the rear azores high preparing to ridge in.

Hate sounding like a killjoy, im still hoping but the 00z runs have done nothing to increase that hope personally..

[johnholmes]

Be nice if people could comment as well on the tweets they post!

 

here here Nick, what is the point of a tweet anyway?

Currently the anomaly charts keep the +ve heights and ridging across the top of their charts but still unclear to me if this is going to bring deep cold into the UK.

Edited January 31, 2017 by johnholmes

[Day 10]

Well we sit in a much better place than a few days ago.

Nice to see that scandi block forming to the north east. Also even better to see the UKMO on board and actually showing the better option at present out of the big 3.

For me the UKMO has performed really well this winter with possible "proper cold spells" shown by the ECM & GFS, with the UKMO having none of it and being right each time. So this time around very good to see all 3 showing similar to the north east at 144.

Plenty to be positive about. "All good things come to those who wait"  that phrase is about to be tested.

[TEITS]

Lack of posts from me is simply due to past disappointments from similiar synoptics.

Seems to me the models are struggling with the low pressure systems for this weekend, combined with the blocking to our NE makes the outlook very difficult to predict. At this stage all we can do is look and see if all models are bringing the cold pool closer to the UK. The answer is yes compared with yesterdays 0Z, GEM especially.

Just add im not even bothering with the ensembles at this stage.

[northwestsnow]

19 minutes ago, TEITS said:

Lack of posts from me is simply due to past disappointments from similiar synoptics.

Seems to me the models are struggling with the low pressure systems for this weekend, combined with the blocking to our NE makes the outlook very difficult to predict. At this stage all we can do is look and see if all models are bringing the cold pool closer to the UK. The answer is yes compared with yesterdays 0Z, GEM especially.

Just add im not even bothering with the ensembles at this stage.

Think there is an element of truth in the 1st part Dave, it seems whatever can go wrong will go wrong for us .I mentioned the azores high yesterday and its still there this morning doing its level best to block the westwards movement of the deep cold to the east.ukmo is better at 144 but for my money there is too much energy in the northern arm ( when isnt there) to allow for what we need, i totally agree with the part about the ens as well, the distribution of energy at that critical 120 - 144 timeframe will or should be better modelled by the ops.

Again hope springs eternal and there will be changes one would be a fool to write off a cold spell but as in my previous post its hope as it stands not expectation.

[chris55]

GEM lands that mega cold pool perfectly on the 00z

ECM very different keeping it way way to the east

Even though ECM takes the initial cold pool away to the east a slower evolution could well develop another attempt into mid Feb.

really interesting output for sure  

 

[Ali1977]

Slightly better heights in Scandy at 144, with the flow from the East knocking on the door. Also of note is the lower pressure in and around Southern Europe.  We aren't opening the flood gates from the East but another small step in the right direction maybe.

[Man With Beard]

1 hour ago, Summer Sun said:

Keep the tweets coming please, they contain the stuff Ian would have been posting in here if it hadn't been for that Facebook copy and paste job...

ECM mean T240 - lots to be watching for here:

An east-based split in the vortex very much in evidence now even on the mean chart. There's still a way to go from this to cold but you can see a clear route from the NE.

But developments to the west need watching too. The Azores ridge looks more likely to break through on the Greenland side of the Atlantic low rather than the Iberian side. If that happens, great news for a wintry mid-February - in fact, that's probably the best bit of all. It may well mean the ridge from the Azores will meet heights to our north, cutting the Atlantic low from its mother-ship vortex in Canada. With heights having preferred the northern route rather than the Iberian route, the Atlantic low would then sink towards the continent. Resulting in - possibly - one of the mega-runs we've seen recently. GEFS number 3 shows the possible progression:

becoming this just 48 hours later:

  

 

 

[chris55]

GFS 144

good shape to the Artic high incoming, question is how will the Azores ridge and Atlantic low interact 

[Ali1977]

8 minutes ago, chris55 said:

GFS 144

good shape to the Artic high incoming, question is how will the Azores ridge and Atlantic low interact 

The azores ridge could link with the Scandy high on this run an re-enforce it, but this may keep the cold to the East AGAIN.  Whilst 850s aren't much better this run, surface cold is creeping our way.  Can't post pics sorry.

At 174 the Scandy high also seems to be growing, and hopefully it'll bulge NW towards Greenland. Oh and the azores ridge is being pushed away, could be game on.

Edited January 31, 2017 by Ali1977

[chris55]

Centre of the holding steady (not sinking)

And now the Azores ridge has been squashed ahead we may get a decent undercut.

[festivalking]

What a glorious chart! 10 days away though 

[chris55]

Cold pool makes it at day 10, chilly!

[Ali1977]

Out to day 10 the GFS is a great run, the Scandy high is very strong and persistant in location.  Hopefully backed up by a better set of ENS and 12Z runs.  A very cold cold pool with us by day 9, looks like it will last a fair while too if correct.

Over the last few weeks its felt like winter is over on here, and expectancy decreases. If we can get a very cold mid/late Feb it will feel better and more of a surprise, and no doubt be buzzing on here more than in a normal freeze I reckon - so fingers crossed.

Edit - SLIDER ALERT next weekend - miles away I know!!

Edited January 31, 2017 by Ali1977

[northwestsnow]

2 minutes ago, chris55 said:

Cold pool makes it at day 10, chilly!

Yes gfs6z is better chris with the cold air into Blighty by day 10, snow showers spreading in from the east..:-)

Azores high out of the way hurrrrrah !

:-D

Edited January 31, 2017 by northwestsnow

[Man With Beard]

Only one way this run is going

 

[TEITS]

Classic example of why I don't use the ensembles.

The 0Z for Berlin was a massive outlier and yet 06Z continues with the trend.