Model output discussion - 1st December onwards

[feb1991blizzard]

14 minutes ago, THE CHOSEN ONE said:

No scandi high - but posts the anomaly chart which shows a huge +VE anomaly close to scandi ...

the question isnt whether there will be a High pressure over scandi - its whether the undercut allows the cold to allign west towards the UK - not SW to france or south to Greece....

s

6z is about to have another go deep in FI.

[booferking]

And the trend continues. 

[northwestsnow]

GFS continues the trend of building heights to the NE, if nothing else, as noted by Bluearmy, it should help send the jet into Europe and erode that horrid euro high. 

[feb1991blizzard]

And delivers a right old tonking as well, I still feel its too premature but would obviously rather see a signal occurring (from the POV of getting cold into the UK) than none at all, I always think in these scenarios though with frigid uppers in a an Easterly, I like to see a lot of GEFS members flatlining at -10 rather than just the odd rogue one or a right up-down-up-down zig zag style + you want solid agreement on exactly how the cold is to be achieved.

Edited December 25, 2015 by feb1991blizzard

[Snowman.]

GFS may not get to an Easterly but it still ends on the same note as all its other runs have.

Seriously disrupted tropospheric vortex with the prospects of blocking.

[bluearmy]

whilst the runs fiddle around with different scenarios in the mid and longer term, the lesson to take is quite simply the damage being done to the trop p/v as can be seen by the back end of each run and the ens members. 

in respect of the remainder of winter, the question is whether the trop vortex disruption will be mirrored higher up. If it isn't, it's pretty difficult to believe that the trop vortex won't reform and drive a positive AO again through late January. 

These op runs are fun to watch but they really should only be viewed in broad terms re the different areas of high/low heights, cold/warm air masses and their potential interaction. (Rather than will it snow in my back garden)

[northwestsnow]

7 minutes ago, bluearmy said:

whilst the runs fiddle around with different scenarios in the mid and longer term, the lesson to take is quite simply the damage being done to the trop p/v as can be seen by the back end of each run and the ens members. 

in respect of the remainder of winter, the question is whether the trop vortex disruption will be mirrored higher up. If it isn't, it's pretty difficult to believe that the trop vortex won't reform and drive a positive AO again through late January. 

These op runs are fun to watch but they really should only be viewed in broad terms re the different areas of high/low heights, cold/warm air masses and their potential interaction. (Rather than will it snow in my back garden)

Absolutely Blue - i was really shocked to see members not seeing the change overnight (euro models), GFS began advertising this trend yesterday and actually the GEM the day before that.

Whilst it is impossible to know whether the trend will continue,as it stands,there are some meaningful straws for coldies to grasp.

But to ignore or deny the changes is incorrect imho.

FWIW as we see on 06gfs the 'initial' block does the job of splitting the jet - at that point we are in the game.

edit and by the end of the run the euro high is disolved and blocking is the headline, extensive blocking at that!!

Edited December 25, 2015 by northwestsnow

[mulzy]

We really need to keep our feet on the ground.  The London ECM temperature ensembles do show a cooling trend and probably the best set we've had in a while but caution is still required.

Merry Xmas all - have a fun day!

Edited December 25, 2015 by mulzy

[knocker]

The ext ecm anomaly is giving a trough from the Baltic down to Greece by the 9th with the HP nudging up from the south which is likely in increase according to the EC32 during  the next week.  The ridging over N. Russia is in decline and there is no obvious disruption of the trop vortex. If there are straws for the coldies to clutch they are invisible to me.

Edited December 25, 2015 by knocker

[northwestsnow]

2 minutes ago, knocker said:

The ext ecm anomaly is giving a trough from the Baltic down to Greece by the 9th with the HP nudging up from the south which is likely in increase according to the EC32 during  the next week.  The ridging over N. Russia is in decline and there is no obvious disruption of the trop vortex.

I wouldnt worry about that, ecm is clearly playing catch up to GFS as it stands..

[Cloud 10]

ECM ensemble mean at day 10 showing the tell-tale signs of the AO going negative with warm anomalies over the polar regions and colder air being displaced to lower lattitudes.

 

 

At least we now have tickets for the lottery.

[booferking]

One thing is for sure we are in for a change of sorts. Vortex just got distroyed

Edited December 25, 2015 by booferking

[East_England_Stormchaser91]

GEM has actually been very good at picking the correct trends this year. Started with this one, and also foresaw the scorching plume we got back in July before any others. Hats off! 

Hope everyone enjoys their Christmas turkey's

[knocker]

5 minutes ago, Cloud 10 said:

ECM ensemble mean at day 10 showing the tell-tale signs of the AO going negative with warm anomalies over the polar regions and colder air being displaced to lower lattitudes.

The ecm is forecasting a positive NAO and AO until the 25th jan.

Edited December 25, 2015 by knocker

[Gustywind]

Reading this thread, "you say potato" etc springs to mind sometimes.

[Methuselah]

Merry Christmas everyone...

Looks like we might be about to exchange our long-lived Euro High for an unfortunately aligned Scandiish type effort...?

[knocker]

Although approaching nearer normality the GEFS temp anomaly is still positive by the end of the run.

 

Edited December 25, 2015 by knocker

[steveinsussex]

22 minutes ago, Gustywind said:

Reading this thread, "you say potato" etc springs to mind sometimes.

SPRING?! 

[lorenzo]

Made these the other night after it looked like we had moved from KW noise to coherent MJO.

These are individual dates for the MJO for January in phase 6 where we have a Nino in place. Very small dataset however does point to evolution that models are hinting at in places. First is Phase 6 Nino for Jan, then rolled forward 10 and 20 days.

The movement east of the Scandi HP well advertised on the first plot, it's the next 10 day roll forward that may be of more interest..

[IDO]

As I will maintain the GFS 06z and 18z have a habit of producing outliers and the op and control today again show little support for cold: 

Best to ignore the changeable ops at the moment as their tendency to go into haywire mode is well known. The LR forecasts offer a temporary cooler period, closer to seasonal averages, from late December, as the wave slowly moves east. The UK will be prone to more of a PM flow. However neither the CFS or the JMA have this more than 5-7 days before we are back in the default late Autumn/Winter synoptic:

JMA: CFS: 

Much like Knocker alludes to viz a viz the ECM. These temporary amplifications will be few and far between in the first two months of the winter and we really need to get some luck to benefit, otherwise it could be a long search for cold. Anyway it appears that the temporary block will be over NW Russia, so lots need to go right to get a lucky break with that setup. The first undercut attempt around D5 is unlikely to be successful due to the lower heights being too strong and any disruption looks minimal:

T120 Control:    T120 OP:   T240 OP: 

D10 and the op has another go, but I can't help feeling that if that happens we will again have too much energy going over the top. Early days yet but confidence low in second attempt at an undercut. The GEM played with this a few runs ago but has ditched it now and is now over doing the Azores/Euro combo, so I suspect it is also currently wrong; somewhere in between is the likely outcome. Its D10 mean suggests that:

D10 GEM:   D10 GEM Mean: 

The GEFS NAO and AO look like staying in positive territory much like the ECM:

Looking at the MJO it is apparent that it is flying through the phases and maybe COD after D14? So it could be all back to the ENSO pattern after this wave has diminished. The question is can we get anything out of this brief interlude from the ongoing pattern?

 

Edited December 25, 2015 by IDO

[bluearmy]

knocker is right to point out the reality of the extended means. However, what has changed over the past 48 hours is that the week 2 colder and more blocked evolutions are no longer inconceivable based in the means/anomolys. Add to that the damage that will be done to the trop and potentially the strat p/v and we have January possibilities for cold. as far as the EC 32 is concerned, weeks 3 and 4 means/anoms are notoriously poor for taking on board a change in the pattern. 

If ian were around, I suspect he would confirm a cluster of colder options now appearing in the week 2 ECM ens. 

[Bristawl Si]

1 hour ago, *Sub*Zero* said:

6z putting Greece and Turkey into the freezer  Popular summer destinations for sunshine & heat, but may be a good bet for some frigid winter weather into the new year...  

 

Similar synoptics to the winters of the early/mid noughties

[Mucka]

8 hours ago, CreweCold said:

UKMO looks to be on board this morning.....

No Atlantic steam roller there...

GFS 180 hrs....

Very, very close

204 hrs we have trough disruption and cold pool backing West

 

 

Merry Xmas ecerybody,

Yeah I would say UKMO has pretty much gone from worse to first this morning, ridge getting into the higher latitudes and importantly we can see energy moving SE undercutting at 144.

JMA looks solid enough although it only goes out to 86h in the morning.

ECM has taken another small step toward GFS and GFS itself has maintained the theme of the block holding on and some trough disruption into FI which would bring in any Easterly.

So many positives but maintaining balance we still have to accept that ECM does not show cold and GFS is marginal. GFS ensembles are by no means fully on board and they are going to have to be dragged kicking and screaming into an easterly solution it seems. And then there is the MetO themselves who are very bullish about no cold signal as it is unusual for them to mention strong probabilities one way or the other in the 30 day outlook and they are still saying low probability of any prolonged cold. (or cold spell rather than transient cold from PM air)

But let's end on a positive. ECM ensembles while not showing cold are trending the right way and are much improved from yesterday.

I do find it odd the MetO are so bullish when we have such a setup on our doorstep as it undeniably increases the options for cold from where we are now. They obviously have data we don't see and of course the expertise and sure cold is still not the favoured option as things stand but I don't get how they can be bullish about no cold given the output and trend this morning. Perhaps we will see a slow a retreat in the next few updates, we can but hope.

Edited December 25, 2015 by Mucka

[forecaster]

11 hours ago, swilliam said:

Ensembles and their means are averages so as you say are not prone to swings. They are extremely useful if the weather turns out to be near average as of course it often does. However when the weather deviates far from average then ensembles are well pretty average at predicting this. This has been highlighted IMO by this month which has been exceptional by any standards. However I do not recall any extended products predicting this level of extreme temperature excursion. Extended range forecasting based on ensembles is good at saying it will be a bit colder/warmer wetter/drier etc but in terms of predicting significant deviations from this are currently fairly poor. So if you are looking for any kind of significant deviation from the norm the ensembles IMO are not that helpful - only in identifying trends. I tend to use them as many do on here as to what the possibilities are going forward are rather than what they are showing as a mean as that is nearly always not far from average (or the default zonal set up). The current situation is a good example of this. There is clearly potential; for a significantly colder/drier spell but based on ensembles you would not state this publicly in forecast  (if that is what you do professionally).  Hence the current forecast from Meto but to most people what is stated means there will not be any significantly colder weather in the next month. So if it transpires that there is then this will be a busted forecast as far as most people are concerned.

On a separate note as  a physical scientist in another field it seems strange to me that modelling is done by feeding in what is effectively adjusted (or duff) data and seeing what the result would be (i.e. the ensembles) and then take an average as prediction.

 

 

 

Essentially agree. Always will be hard for ensembles to pick the extent of the extremity, but the ECMWF do have their Extreme Forecast Index which is pretty good. The way they decide how to "duff the data" is quite interesting in itself (and way beyond me). I think they invest a lot of computing time into picking which things to perturb, and where they should be perturbed. If the atmosphere weren't chaotic, and if we could analyse it perfectly, would be no need to duff things up

[winterof79]

1 hour ago, northwestsnow said:

GFS continues the trend of building heights to the NE, if nothing else, as noted by Bluearmy, it should help send the jet into Europe and erode that horrid euro high. 

Horrid unless your in Portugal for Christmas.Then it can get nuked.