Hunt For Cold: Model Discussion - Heading Into Christmas

[Guest Delete Me]

You Londoners can't handle gravy, never-mind snow!

My bets are, unfortunately, on a SSW failing to have a proper impact on the UK leaving us at the mercy of the Atlantic

[feb1991blizzard]

29 minutes ago, Nick L said:

No. You said that an SSW means nothing which is completely and utterly untrue. 

In fact you could almost reverse that and say we have only had 2 times in the last Decade where we have had potent cold spells without an SSW, and because the Dec 09 / 10 spells were so early, you could almost say they were freaks anyway, 2018 and 2013 we have had big reversals followed by either potent or long lasting cold, they are the only 2 SSW's before this one since Feb 2010, can't think of any other either very potent or very long lasting cold episodes during that time, possibly Feb 2012 excepted and that was a very near SSW.

[kold weather]

This is looking more like the late 90s version of a SSW which unfortunately didn't really effect the troposphere all that much i a way desirable for us. Any response may take some time, but barely a hint of any northern blocking anywhere at all, pretty flat flow.

Indeed 06z shows the PV pulling itself into almost one coherent structure again towards the end.

Cold zonality is an option, but at least in short-med term for I'd bank on more of a SW slant to the winds unfortunately.

 

Edited December 27, 2018 by kold weather

[Daniel*]

I don’t see any need to feel abject morning models were definitely a big swing in right direction! At least it looks sufficient cold pooling is going to be east. Ridge should be more durable...

[Methuselah]

11 minutes ago, kold weather said:

This is looking more like the late 90s version of a SSW which unfortunately didn't really effect the troposphere all that much i a way desirable for us. Any response may take some time, but barely a hint of any northern blocking anywhere at all, pretty flat flow.

Indeed 06z shows the PV pulling itself into almost one coherent structure again towards the end.

Cold zonality is an option, but at least in short-med term for I'd bank on more of a SW slant to the winds unfortunately.

Indeed Kold...The Lobe of Death awaits?

[Man With Beard]

1 hour ago, bluearmy said:

 

 

 

Glad half empty syndrome MWB...... the clusters reveal what I thought they might. No need to be downbeat - the gfs type cluster in the ext now below 50% and the other two split between an increasingly wintry looking developing mid Atlantic/ n Atlantic ridging scenario and the balance of the mobile cluster sheared away to a sliding type scenario against a scandi blocking signal. 

The trend is good imo ......

Have to say, the clusters make the ensembles look a bit better than you would think from flicking through the individual members! 

Yes that cluster 2 (Atlantic ridge) was there when I looked at them individually, but cluster 3 makes the ridge to the NE look a bit nearer than I'd thought... but glass half full, let's hope that ridge drifts westward

From a personal point of view, I'm still well prepared to ditch the ensembles if the effects of the SSW haven't been fully factored in yet 

[kold weather]

Just now, Ed Stone said:

Indeed Kold...The Lobe of Death awaits?

The ECM is definitely much better and there is some potential, but it was on the colder side of the ensembles. the 06z  GFS pretty much a write off for the first 15-20 days of next month with a flow like that at least. That run could have come straight out of 97-98 or 88-89, etc

[snowrye]

Reading all these posts is utterly confusing,1 posts 1 thing,1 posts something completely opposite,and on top of that,the hunt for cold thread,has turned into the ssw thread,seems all hope is being pinned on this,although it doesn't guarantee cold,I admit,I know very little about it,but even though its only december,it seems this will be make or break the winter,seems to be getting harder and harder every winter,yes,we had a mini beast from east in march,but from a snow perspective,It wasn't that great in my location,compared to places only a couple of miles up the rd.

[northwestsnow]

1 hour ago, bluearmy said:

 

 

 

Glad half empty syndrome MWB...... the clusters reveal what I thought they might. No need to be downbeat - the gfs type cluster in the ext now below 50% and the other two split between an increasingly wintry looking developing mid Atlantic/ n Atlantic ridging scenario and the balance of the mobile cluster sheared away to a sliding type scenario against a scandi blocking signal. 

The trend is good imo ......

I will go with that Blue-

Only my amateur opinion but i'm feeling much more upbeat this morning..

I mentioned the scandy high much earlier this morning- thats the direction we are moving too in my very humble opinion..

[Weathizard]

@snowrye People having different opinions on an Internet forum is hardly surprising is it, I haven’t seen any confusing posts this morning/afternoon, been good discussion IMO^

The problem is we don’t have much to discuss at the moment, it’s a pretty dull time to be model watching so of course attentions are going to turn to the strat warming as if we didn’t have that right now we’d all be even further in the dumps! Time will tell if it delivers for us, still 2 months of winter left things can change rapidly.

Edited December 27, 2018 by Weathizard

[Wilxy]

Not sure why people are negative output this morning has potential and that is enough to keep me interested!

All 3 have a decent cold pool to are east! not a bad place to be in at the beginning of January

If that fails then mark the 4th of Feb on the calendar!

  

Edited December 27, 2018 by tomjwlx

[Guest]

Cold Zonality, well if thats the best we can get currently it will have to do, now to deal with the stress of the uppers being marginal unless you live at altitude or in Scotland, well you lot enjoy that debate and i shall sit here and count me snaw flakes. still plenty of life let in this winter yet and dont forget early spring always has the chance to deliver.

[Guest]

The Models Are Just Starting to Sniff Out the Major Pattern Changes - Better Late Than Never!

As expected the models were almost certain to struggle dealing with the exceptional changes in the background signals - they almost always do.  There are even inconsistencies within the same models' different type of output on the same run which is almost unbelievable. I will start with GFS who have struggled more than most. I'll refer to today's 6z run.  We know that they have been indicating an SSW for several weeks now. Their strat charts have played around with the timing, the extent and the type of SSW but their pressure charts still bear little resemblance to their strat charts. The same goes for their mjo output which is the polar opposite to what the pressure charts are showing.  Always useful to remember that it is the background signals to controls the model output (when the models take note!) not the other way around.  

  

The SSW is taking place now and some of the GFS strat output is already showing an imminent wind reversal (see the strat thread for details) and the earliest signs are already been seen in North Asia (more on that below). This 10hPa chart is for day 10 and shows a thoroughly disrupted SPV (stratospheric polar vortex) with both a displaced and split SPV.  

  

At no stage in this run does GFS show wind reversals at the surface in the Arctic on their pressure charts (this was the same in the run up to the "beast" following the February SSW until about a week before the full surface impacts). The day 10 chart on the op run actually shows a reasonably well organised PV with a default westerly flow and no reversal.  Some HP has built across from both the Alaskan and Siberian sides of the Arctic but this chart is so far from correlating to their strat and mjo other output that it only serves to magnify the serious deficiencies in the main model and it seems clear that their nwp either does not have a sufficient data feed of both the strat and the tropical atmosphere or it is far too biased with the default always towards climatology. 

This is the GEFS panel for the same time. None of the ensemble members show a full reversal at the surface but about 6 or 7 do have HP building northwards or north eastwards which is a move in the right direction but even these do not represent their other data.

GEFS has been going for steadily higher amplitude as the MJO progresses through phase 5.  In fact it goes off the scale through phase 6 during next week and is predicted to enter phase 7 at near record high amp much as it did back in February during the last SSW.  The chart is actually the "bias corrected" version!  

The ECM chart has the MJO at much lower amp and is more progressive through the phases but it has been slowly increasing amp during the last couple of days.  The tropical forcing has been suggestive of a generally higher amp but GEFS is still the only model to go for the "extreme" outcome.  It may well be that we'll see a model convergence with reasonable amp (more like the JMA position below) but week 2 MJO forecasts are notoriously unreliable and subject to change. Overall, the current consensus would be to progress towards phases 6 and 7 (and later on to 8 and 1) as we move though the first week of January and increasingly favouring HLB with a few days time lag to likely impacts - perhaps around days 10 to 15 or January 6th-11th which has been the more widely favoured period for some time.

 

The other models also show a mix of outcomes although most show the HP to our south building northwards (not always decisively) and the trend is now suggesting that they are just beginning to pick up on some of the changes in the background signals.  Most of the other charts have already been posted on here and it's encouraging to see ECM trying to produce a more amplified scenario, so I will move on to several other "key" charts.

The "StormSurf " charts are based on NASA output but I'm only looking at current and short term changes. In my recent posts, I've been referring to the vast expanse of HP over much of central and northern Asia, Russia and Siberia - well that is now even more intense exceeding 1060mb in northern Asia. It's that area which is seeing the initial impacts from the SSW.  Strong northern Asian blocking is one of the precursors to the lower tropospheric layers being receptive to propagation from the stratosphere and full coupling.

 

Now the highly important influence of GLAAM (global atmospheric angular momentum) and the torques.  Total GLAAM is still +ve but has fallen recently.  The relative GLAAM tendency anomaly was +ve, then fell back very briefly to quite strongly -ve and is now rising strongly again precisely as anticipated. FT (frictional torque) is also rising. I have not shown the latest AAM and FT charts this time but I'll move on to MT (mountain torque). In my last couple of updates, I said that +ve EAMT (east Asian mountain torque) was extremely important in both this part of the process as well as playing an assisting role in triggering major SSWs. The previous spike in GLMT (global mountain torque - the black line) was around Dec 7th.  It then nose-dived to be temporarily strongly-ve around Dec 19th and was predicted to bounce back very quickly to go strongly +ve again around now.  The charts are always 2 days behind and are usually updated at around 1430 GMT - so this one is yesterday's chart for Dec 24th. It looks like GLMT is already +ve and probably still climbing right now.  EAMT (the red line) has been following GLMT as a main component of it.  If you refer to the top part of the chart which shows the regional torque latitudinal distribution we can see that the last +ve EAMT event is depicted by the deep red blob around Dec 5th to 10th and centred around lat 32N to 45N - which is just north of the Himalayas and across the Tibetan Plateau up to the Mongolian Mountains. The uplift from that event fed planetary waves right up into at least the upper stratosphere and this (with the time lagged response of a few days) helped to further weaken the SPV. Then we had that short period of -ve EAMT depicted by those blue blobs in the same region. Now we are seeing the next +ve spike which may well be as strong as or even stronger than the last one. This is perfect timing as within a day or two it is likely to send up further vertically propagating planetary waves which should help to finish off the SPV during next week if it still needs a final attack. The other benefit is that the strong +ve EAMT right now and for several more days is part of the surface pressure process propping up the huge HP block to the north.  It's all more complex than this and I'm still learning about these processes.  Just accept that what is going on now is part of a much larger process and it's all helping to "prime" the surface layers for SSW impacts.

Although no atmospheric changes in our meteorological world can be predicted with absolute certainty, the changes in the background signals and the broader pattern reset gives us a real insight into what we are "likely" to see several weeks ahead.  The models almost always struggle to take full account of these changes often up until a week or so in advance. This is a very significant SSW event but there "were" problems with timing issues, strength, type (displacement and/or split), the extent of downward propagation and the position and longevity of surface impacts. While that is still not 100% resolved, things are a lot clearer now.  The tropical forcing and the teleconnective link between AAM, the torques, the MJO and the strat are all coming together more or less as predicted several weeks ago. I expect the models to increasingly factor in the significance of these changes during the next few runs. By the time we reach the New Year we "should" be very close to the fuller impacts showing up on the day 7 charts.  So expect a mix of eye candy and less progressive runs and the usual roller coaster on here for a couple more days as they adjust.  I remain very confident of a pretty prolonged cold spell in Europe, the UK and the eastern CONUS starting to take hold as we move into early January.  Monitoring all the changes will be incredibly fascinating.  I'll leave you to it for a few days and hope to come back to a much more optimistic thread.  David  

Edited December 27, 2018 by Guest
check charts and correct typos

[Methuselah]

10 minutes ago, More Snow said:

Cold Zonality, well if thats the best we can get currently it will have to do, now to deal with the stress of the uppers being marginal unless you live at altitude or in Scotland, well you lot enjoy that debate and i shall sit here and count me snaw flakes. still plenty of life let in this winter yet and dont forget early spring always has the chance to deliver.

Indeed MS - totally LoB-dominated winters are very rare, IMO, and I can only think of 1974-75, 1988-1989 and 1997-98 as winters that would really qualify...So no reason to write off winter, at this juncture...

[BARRY]

37 minutes ago, Ed Stone said:

Indeed MS - totally LoB-dominated winters are very rare, IMO, and I can only think of 1974-75, 1988-1989 and 1997-98 as winters that would really qualify...So no reason to write off winter, at this juncture...

Time will tell been on here a long time. have learnt to be patient 

[snowray]

1 hour ago, tomjwlx said:

Not sure why people are negative output this morning has potential and that is enough to keep me interested!

All 3 have a decent cold pool to are east! not a bad place to be in at the beginning of January

If that fails then mark the 4th of Feb on the calendar!

  

Well the ICON will start to roll out shortly, it certainly will be interesting to see if it sticks to its guns, if it does then we may see further improvements from GFS. Although I'm still inclined to think that FV3 is closer to the mark in FI with a cold north westerly followed by a slow but sure disintegration of the vortex starting around mid January.

[tinybill]

http://www.meteociel.fr/modeles/cmc_cartes.php?code=15&ech=192&carte=1

some thing to keep people interested  at  the moment

[markw2680]

The post from David (bring back62-63) is absolutely brilliant and that is the exact reason why not to be taken in by every model run atm as impacts from ssw aren’t even been seen there yet. The lovely word patience springs to mind again

its very hard not to take each run as gospel especially when we get the commentary of every frame lol, I do struggle with that tbh but each to there own I suppose. Anyway let’s hopefully all enjoy the changes (upgrades of next few days) together

[Reversal]

Is there any actual evidence that models are slow to take the effects of a SSW into account until it's under way. Similarly, it has been suggested here that the models are yet to factor in the impacts of the MJO.

It doesn't seem logical to say the GFS is not taking the amplitude of the MJO phase into account. And then make an independent forecast based of a GFS MJO plot... Similarly with strat impacts.

It's seems likely that the GFS/ECM/UKMO take many more drivers, signals and data into account than any human ever could when coming up with a forecast. Perhaps it's us enthusiast's are the ones failing to take drivers into account. And within there lies the mismatch between our expectations and NWP output, not the other way around.

Edited December 27, 2018 by Reversal

[karyo]

The 12z ICON is a bit underwhelming compared to the earlier output. At 126 hours the high is over the UK on the current output as opposed to the 0z when it was over Iceland.

[karlos1983]

1 minute ago, karyo said:

The 12z ICON is a bit underwhelming compared to the earlier output. At 126 hours the high is over the UK on the current output as opposed to the 0z when it was over Iceland.

Yes nowhere near as good, we lose the ridge into Greenland.  

[swfc]

4 minutes ago, karyo said:

The 12z ICON is a bit underwhelming compared to the earlier output. At 126 hours the high is over the UK on the current output as opposed to the 0z when it was over Iceland.

Yes its another one which is ebbing away from Greenland.mayby off to the east tho!!!

Edited December 27, 2018 by swfc

[Methuselah]

1 hour ago, Ed Stone said:

Indeed MS - totally LoB-dominated winters are very rare, IMO, and I can only think of 1974-75, 1988-1989 and 1997-98 as winters that would really qualify...So no reason to write off winter, at this juncture...

PS: I did of course intend to type 'LoD' for Lobe of Death!

[Swave Snow]

6 minutes ago, karyo said:

The 12z ICON is a bit underwhelming compared to the earlier output. At 126 hours the high is over the UK on the current output as opposed to the 0z when it was over Iceland.

Great then GFS and ECM will be ok then lol

[mountain shadow]

9 minutes ago, karyo said:

The 12z ICON is a bit underwhelming compared to the earlier output. At 126 hours the high is over the UK on the current output as opposed to the 0z when it was over Iceland.

That can't be right? Six hours ago the ICON was the bestest model ever.