Focussed Model Discussion

[bluearmy]

18 minutes ago, knocker said:

The ecm NH analysis at T240 is not a million miles away from the end of the det run, It then develops along similar lines to recently. Ergo, very amplified upstream with the Alaskan ridge/ vortex trough complex with a strong upper flow exiting the eastern seaboard around the renewed Bermuda high pressure towards the trough over the UK. But this is complicated by the ridge into eastern Greenland and the flow diverging around it thus a much weaker flow in the eastern Atlantic and colder air advecting into the now intensifying trough I'll leave surface analysis to the det runs but temps way below average

One ridge sticks to the west and the consequences are significant for nw Europe as we lose the warm sectors. Even a decent amplification would encourage the next dive to be far enough west to keep the uk on the cold side throughout a cycle. 

[Paul]

Overnight GEFS anomalies still staying on course for a switch to colder weather. 

Pressure anomaly for the end of the month is definitely conducive to cold weather. 

Temperature anomalies back that up. We start the upcoming week colder than average, that lifts out toward the end of the week, but then into the freezer for Northern and Western Europe by the end of the month.

Early next week:  

End of the week: 

End of the month: 

 

[lorenzo]

Interesting morning and really encouraging IMO in terms of the set of model suites we were looking at on Thursday and Friday being chipped away at then collapsing into something else late Friday into Saturday morning. Given the up close review of each run, and I get that, it is a time where the deck remains stacked in our favour. However, given the long lead on the SSW, the count down to it happening, the displacement and then elongation in time of the SSW via the vortex split. I think this has generated fatigue, it's certainly been a long watch!

The AO profile overall, whilst an output vs. a driver shows the trend and this looks solid as Jan ends, this is supported by both the Strat Temp Anoms and NAM 'paint drip'. There have been hints of the AO dropping to -3 and 04 SD, without 'fully' getting there. I think it is an eventuality vs a jam tomorrow. Indeed that phrase is getting used a lot, to contextualise - the after effects of an SSW 'will be' jam tomorrow given the lead times for imprints on the atmosphere..

 

AAM and GWO dynamics illustrated below, relative AAM courtesy of torque activity, gives a steer on expecting to see blocking regimes manifest, as does the SSW, so a double ingredient here.

From this morning's GFS we can see from around Day 9 both the AO starting to drop again and also blocking coming online over Greenland, c 26th is where the trend commences to elevate heights here, and there is a lot of energy firing towards Nuuk to start causing the Arctic profile to shuffle.

ECM goes back to something akin to the earlier ENS and just needs some sharper inflection to do similar damage and mirror it's weeklies.

I would say the US Storm, impacts on the jet, careering into the NE Canadian portion of the vortex as we all have seen collapsing the nirvana charts on offer at the end of last week has played through the system now, models catching onto again the true sense of direction. That wave guide remains, the signals for HLB remains, the down welling remains, the AO tendency remains, the AAM increase is there. Whilst the hyperbole of no definitive easterly programming from 210 down to 0 hrs created despondency, there is a lot that remains bloody good for - the end of January with a ton of winter left.

[knocker]

8 minutes ago, bluearmy said:

One ridge sticks to the west and the consequences are significant for nw Europe as we lose the warm sectors. Even a decent amplification would encourage the next dive to be far enough west to keep the uk on the cold side throughout a cycle. 

Without getting too hung up on detail at this stage another scenario could easily be a very slack area of low pressure that could well imitate some very cold temperatures and quite severe frosts.

[bluearmy]

4 minutes ago, knocker said:

Without getting too hung up on detail at this stage another scenario could easily be a very slack area of low pressure that could well imitate some very cold temperatures and quite severe frosts.

It is but I can’t see the Canadian lobe relenting enough for the pattern to stagnate without the ridge as an initial catalyst .....otherwise I think we stay in a repeating cycle which would eventually either blow itself out or back west to bring your scenario into place 

[knocker]

2 minutes ago, bluearmy said:

It is but I can’t see the Canadian lobe relenting enough for the pattern to stagnate without the ridge as an initial catalyst .....otherwise I think we stay in a repeating cycle which would eventually either blow itself out or back west to bring your scenario into place 

I also don't think the vortex will relent that much so, as ever, it will depend on the distribution of energy downstream

[Duane S.]

Ha ha, good old Navgem. Carrys on shrugging its shoulders and saying “why all the fuss folks? Chill, I’ve got this”

Relatively speaking though, a very good set of 00Zs for long term cold. 

[johnholmes]

No sign of any change in the anomaly charts=cold will remain, how cold is for the synoptic models at much shorter time scales.

The EC and GFS remain more bullish than NOAA but it also shows no sign of any milder interludes in the overall upper air pattern through the next two weeks.

All 3 shows fairly cold contour heights.

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

http://www.cpc.ncep.noaa.gov/products/predictions/610day/500mb.php

[mb018538]

We just have to sit tight i'm afraid folks. Looks like we've missed out this time - but it just highlights the need to take things as a whole rather than individual. We were spoiled with a few OP runs that were either outside the ensemble mean for cold, or right at the bottom end.....all the while there were still a fair number not showing anything really cold materialising. Until you get that cross model and tight ensemble support, then you always need to beware.



As others have pointed out, the deck is still stacked in our favour, and nothing at all is really pointing towards a zonal return any time soon. This is our one step back, the two steps forward will hopfully come as we start February.

[Purga]

Plenty to interest us still. GEFS trend is down and apart from the minor glitch at the end of the week is solidly cold and trending more so.

Understandably, there is some despondency over the 'failed' easterly saga but it's more like a 'watered down' version  of what has been shown all along in a very complex and unusual scenario.

I submit that any cold lover should be pretty pleased with the trends!

18z (yesterday)                                           00z (today)

The generally cold outlook remains with a less cold interlude possible for a day or two towards the end of the coming week. The next few days stay chilly throughout with a snow risk in places. Not deep prolonged cold, nor deep nationwide low level snow, just colder than average.

What is totally absent in the model output is any sign of mildness. If we are to look beyond day 6/7 the cold trend is very clear and this time next week things once again look cold and wintry for the foreseeable.

.

 

[lorenzo]

00z Iceland look... massive signal there...

[kold weather]

Interestingly Lorenzo those -ve NAO seems to be coming forward in time, fairly sure that was a feature that didn't get going till about 300hrs yesterday. Be interesting to see whether we end up getting a more 'true' Greenland high set-up on those clusters later in the run. I also note the 06z GFS is nearly identical in terms of 500hpa placement of the ridges at 240hrs to those clusters so good agreement there.

Lorenzo or anyone else, do you have a link to the clusters?

[lorenzo]

http://brunnur.vedur.is/kort/ec-ens/2019/

[phil nw.]

Yes it is still essentially a cold outlook over the next 10/15 days going by all the means and ens.

The ecm mean at day 7 pretty much sums up the repeating pattern this coming week or so ie. the re-enforcement of the Euro trough from the north west and the Atlantic high to the west so mainly cold polar maritime air across the UK with snowfalls quite likely for higher ground and at times in lower down especially in the north.

.

As we go into week 2 a look at the eps ht anomalies show building cross polar +ve hts starting to link our Atlantic ridge which would indicate the downwelling of the warmings hitting the 500 hPa pattern with reversals in the flow across the Arctic.

A look at the gefs mean anomalies for days 6-10 alongside days 12-16 show how the polar field has developed those +ve heights.Underneath those we see the 5 day mean 2m temp.anomalies for the same periods.

so a trend to an even colder flow setting up in week 2 with air coming from the Arctic ie north/north east as we develop blocking at higher latitudes.Along with that  trend we continue to see the Euro upper trough modeled to our south. 

Edited January 20, 2019 by phil nw.

[Sperrin]

Have to say this is already shaping up to be an excellent thread. None of the bipolar hyperbole of the hunt for cold thread only sensible, balanced and succinct analysis. Great idea that negates the need through dozens of pages of mixed messages. 

[bluearmy]

note that every single gefs member has a diving trough post day 8 .......... it’s the clearest possible indicator that we are in a repeating pattern scenario. what precedes and follows the diving trough will dictate if it’s just a flash (like this week) or part of something more significant re getting widespread lowland snow cover.

agree Phil re the arctic ridge across the pole ....picking up momentum now ...

winter has arrived around the 20th as was trailed .....it’s just not dec 2010 .........yet ....... 

very little chance of pinning down the detail and timings for week 2 ..........asaide from at least one trough diving nw/se somewhere in the east Atlantic sector .......

[phil nw.]

9 minutes ago, bluearmy said:

note that every single gefs member has a diving trough post day 8 .......... it’s the clearest possible indicator that we are in a repeating pattern scenario. what precedes and follows the diving trough will dictate if it’s just a flash (like this week) or part of something more significant re getting widespread lowland snow cover.

agree Phil re the arctic ridge across the pole ....picking up momentum now ...

winter has arrived around the 20th as was trailed .....it’s just not dec 2010 .........yet ....... 

very little chance of pinning down the detail and timings for week 2 ..........asaide from at least one trough diving nw/se somewhere in the east Atlantic sector .......

Yes Nick cross polar ridging looks to be the signature later and the eps clusters, which i guess you have viewed at day 15,show a similar trend.

Looks promising let's hope this evolution is smoother that the one we had hoped for this week.Hopefully a better chance with a wider split of the trop. pv modeled in week 2.

[bluearmy]

17 minutes ago, phil nw. said:

Yes Nick cross polar ridging looks to be the signature later and the eps clusters, which i guess you have viewed at day 15,show a similar trend.

Looks promising let's hope this evolution is smoother that the one we had hoped for this week.Hopefully a better chance with a wider split of the trop. pv modeled in week 2.

Only issue is that it’s not possible that there is only one cluster which means we can’t see how the transitions between pulses of low heights stack up. We could simply rotate through another cycle as we have this next seven days without enough surface cold ....though Im pretty sure that the next dive will be further west of this weeks 

looking through the extended in graphical form for my location reveals that the idea of one cluster is at best fanciful!  

Edited January 20, 2019 by bluearmy

[Day 10]

15 minutes ago, Sperrin said:

Have to say this is already shaping up to be an excellent thread. None of the bipolar hyperbole of the hunt for cold thread only sensible, balanced and succinct analysis. Great idea that negates the need through dozens of pages of mixed messages. 

Totally agree mate, it chops out all the mess and does exactly what it says on the tin 'focused'

6z continuing the trend from it's oz run.

So a chilly/cold week trending colder from the North/North East.

[Purga]

 

06z GEFS shows further firming up on the longer term cold signal

The ECM 00z ensemble suite shows the identical message to the GEFS, i.e. long-term signal for cold weather beyond a very brief blip next Saturday. Most of the variants bring in the warm sector at some point that day but a reasonable cluster delays it until the evening. Note that there's a virtual absence of mild outcomes and very few offering even normal temperatures.

Ensemble suites can also flip but as it is at the moment the outlook remains a cold to very cold one.

 

[Paul]

1 hour ago, Nick F said:

 

Yep, still plenty to be optimistic about today IMO with regards to the general patterns evolving from the medium range modelling, including another attempt from the models at a very cold E or NE flow to end the month into February.

It’s looks like the models may start to firm up on a second attempt at ridging poleward over the Atlantic towards Greenland and Iceland in the last few days of this month, this helped by perhaps more favourable forcing of the MJO cycle for the Atlantic amplification but also the more sustained downwelling of easterly winds from the lower stratopshere down through the troposphere at the end of the month and into early February. This combo of forcing from above and below will hopefully prove more sustained and stronger for high latitude blocking to develop.

Before this potential, there could be some back edge snow on the active cold front sweeping southeast Monday night, followed by wintry showers in the NW following. Wouldn't rule out a few wintry showers for SE England and East Anglia via NE wind on the back of the low dropping into near continent later in the week too, as per 00z EC:

A milder blip perhaps next weekend, as the remnants of the weekend winter storm over NE USA redevelops as a deepening low near Iceland and heads east turning winds westerly. Then we could descend into a stormy spell with lows diving SE into northern Europe, bringing Pm flows that could feature snow for northern areas, before that Atlantic ridge amplifies north and polar height rises from easterly winds developing in the trop from SSW downwelling combine to increase chances of HLB. The EPS for London certainly show the weekend 26/27th milder blip then downward temp trend to end the month:

 

 

[Catacol]

Just for fun - let's use JMA today for a bit of analysis given the good record back in Feb 18. 

Tuesday first of all. While 850s are low enough for snow, just looking at the flow will tell you here that thicknesses are going to be on the wrong side of the line for significant snow. For anywhere away from high ground this will be a cold rain, maybe sleet, event. In essence the trough has not dropped steeply enough to be termed a slider and there is little to no flow off the continent to pull cold, dry air into the mix. A bit disappointing, but it was always one of the options given the angle of attack.

But I think @chionomaniac hit the nail on the head when he talked about a repeating pattern. I assume everyone is now coming around to the likely evolution of 2-3 days of dry and benign weather at the end of the week once the trough drops into place. This always seemed a decent probability given the proximity of the block to the west and the uncertainty surrounding speed of transition to the next pattern phase. Sometimes its good to go back through posts and retrace your own steps a bit on the rollercoaster journey...and from a personal standpoint (like many) I got carried away with the stellar charts that appeared pre Saturday. However back on Wednesday I posted this - "So - the trough drops giving some snow somewhere... then maybe a more stagnant day or 3 at the back end of the week (but still cold) as the pattern settles"....and that was probably a decent gut feeling at a week's range that I should have stuck to. Still - easy to get carried away when the hunt gets hot!

But as the pattern waxes and wanes all roads are still leading in the same direction regardless of grumpiness about the disappointing trend of Weds/Thurs of this week. By Friday the amplification process gets its skates on, and the transition of the ridge becomes apparent with heights pouring from atlantic to scandy

The overnight highest performing ECM backs up this view, though notice the further eastwards progression of a system running over the top...reducing the ability of pressure transfer within that 24 hour window.

However the end product by Sunday is pretty much the same - JMA for Sunday (admittedly yesterday's 12z) sees the trough drop back through the UK once again with block to the west and strong ridging over Russia

Less strong block to the east from ECM but same basic setup

And GEM (note - as good as ECM at 192 in Dec 2108 on verification stats) on the same page also though the trough is much less pronounced

Finally GFS - same again though heights over Russa are quite weak in comparson

So - if we are looking for the next "certainty" in terms of pattern beyond the frustration of the failed easterly this week then we can perhaps look for another cold trough on Sunday 27th (Note - not even February yet!!) to drop in....and maybe this time more mature SSW impacts and move of MJO closer to favoured phases will help it stick with heights to the north. Ensembles certainly say YES. EPS and GEFS below for 3 days later (Weds 30th) all in line for heights increasing after this second slider/drop of trough north to south

What's not to like???????

Edited January 20, 2019 by Catacol

[Day 10]

14 minutes ago, Purga said:

 

06z GEFS shows further firming up on the longer term cold signal

The ECM 00z ensemble suite shows the identical message to the GEFS, i.e. long-term signal for cold weather beyond a very brief blip next Saturday. Most of the variants bring in the warm sector at some point that day but a reasonable cluster delays it until the evening. Note that there's a virtual absence of mild outcomes and very few offering even normal temperatures.

Ensemble suites can also flip but as it is at the moment the outlook remains a cold to very cold one.

 

Lets' hope that milder bump is the last hurrah from the utterly forgettable two thirds of Winter. Maybe that bump indicates the top of the roller coaster as we finally slide in Winter proper, will February make up for all this chasing???

The longer term trend doesn't look too bad atall.

ECM

GFS

[BornFromTheVoid]

2 minutes ago, Quicksilver1989 said:

Well this mornings output suggests that unless there is some utterly spectacular turnaround, an easterly is off the table for now. In fact the 06z swingometers suggest the 25th of January may be quite mild. One exception is P18 but that is the only exception.

 

Longer term though the cold signal is building still and unlike the whole easterly saga this hasn't been out of the blue, suggesting some persistent background signal may be driving it (rather than a volatile and unpredictable signal). Most seem to be getting their cold pool in from a Euro trough rather then some strong northern blocking. P1 has a cold arctic airmass waiting in its wings.

 

Lets hope the Atlantic doesn't fire up from the NE Canada cold pool, its remarkable how far back that cold pool has been pushed back east.

[phil nw.]

2 hours ago, bluearmy said:

Only issue is that it’s not possible that there is only one cluster which means we can’t see how the transitions between pulses of low heights stack up. We could simply rotate through another cycle as we have this next seven days without enough surface cold ....though Im pretty sure that the next dive will be further west of this weeks 

looking through the extended in graphical form for my location reveals that the idea of one cluster is at best fanciful!  

Just been going through those again Nick and it seems frome day 11 they reduce to only one cluster.Indicates that around this time the last ejection of low hts from the Canadian pv is cut off and the ridge heads north.Pattern adjustment to more of a north/north easterly?

Looks like a strong signal for day 11-15 to reduce a scenario to one cluster,unusual at that range for sure.

Edited January 20, 2019 by phil nw.