Model output discussion - 16th Nov onwards

[nick sussex]

Well the ECM hasn't fully backed the UKMO but it has edged the pattern further west and has that ridge extending from the Siberian high nosing in towards Scandi at T144hrs.

 

The jury were about to deliver their verdict but can't agree so we'll see in the morning! The ECM postage stamps out later will be interesting, even though they only go upto to T120hrs they should give us an idea of where the main cluster is in terms of how far west/east the trough disruption will occur.

[blizzard81]

At T192 the vortex getting organised an swinging like Mike Tyson...saying to us how dare you the audacity to try GH an snow in Nov......However Winter is Buster Douglas and the pv knockout punch will come this Dec I can sense it with that SH playing its role...T216 applying pressure to the East

Yes, the pv throwing everything it has got but the siberian high holding it's ground. Fascinating to watch if nothing else.

[phil nw.]

I bet we are all now feeling this much colder and raw northerly as it plunges south for the weekend.

Quite a notable cold snap with temperatures up to 5-6C below normal.

 

A quick look at the anomalies for the next 3 days and then days 4-6 show the current cold which eases later next week as winds turn to the west.

 

The se last to warm up.

 

Looking overall at the charts it seems that the Siberian hights will continue to show for the foreseeable,waxing and waning but just too far east to halt the stronger looking jet building upstream.

UKMO does indeed throw a little tempter at t144hrs but it does look like the forcing from the deepening Greenland vortex will eventualy prevail.

 

[blizzard81]

Interesting...one for experts..could the SH become a hindrance to uk cold holding the vortex in a place to just deliver +NAO stormy Dec weather?

Yes, a very plausible outcome that could lock in for quite sometime. However, the extensive Asian snowcover which is energising the siberian high is really throwing a spanner into the works. I feel the models will struggle with this upcoming battle royale between the PV and SH.

[Liam J]

Some very disturbed charts again this evening showing the UK coming under heavy attack from the Atlantic as the vortex sets up shop to our north, looking very unsettled and stormy going forward. We could be getting through the storm alphabet at a fair old rate, with the possibility of some notable weather if the models are onto the right pattern for the last week of autumn. 

 

I might be wrong but you may find that Siberian high could actually turn out to be a hindrance in the long run... Not sure though, might be barking up the wrong tree it's just I seem to remember from a previous year where people wanted it to disappear? Maybe someone could put me right...

[Frosty.]

Well at last the much talked about Arctic blast is now sweeping south along with wintry showers and snow in places and the Ecm 12z shows a cold weekend across the UK, exacerbated tonight and tomorrow by the strong Northerly winds but most of the UK becomes sunny tomorrow once the showers clear, by Sunday the winds start to ease and back NWly as an atlantic ridge begins to topple SE which gradually kills most of the residual showers around windward coasts but the cold air lingers across the southeast into early next week before joining the rest of the UK in an unsettled, windier spell with temps closer to average. Next week does not look mild, only fleetingly milder at times but generally feeling rather chilly due to the strength of the winds which have north atlantic / polar origins and with quieter interludes with overnight frosts...but the main thing is we have our first cold snap in the bag and looking ahead I think we will have regular shots of polar air in the weeks ahead, especially further north.

Edited November 20, 2015 by Frosty.

[knocker]

The GEFS anomalies are of interest this evening although on there own not greatly significant. The 6-10 has a weird orientation of the Alaska HP with a cut off low to the SW of the US which does influence the source of the airmass hitting part of the UK. The key players are the Greenland low with associated trough down to the ME and ridging Russia. The net result of all this is still unsettled over the UK but less so in the south.

 

But quite a change on the 11-15 with HP over N. America  removal of the Greenland trough and heights building from the south over the UK. This still leaves the latter in a westerly regime but with HP being more influential less unsettled and temps nearer average or possibly even above in the south.

I have a feeling the ecm might not go along with this.

http://www.tropicaltidbits.com/

Edited November 20, 2015 by knocker

[Newberryone]

Latest Ecm 12z output even more amplified than the 00z with those heights to the south flexing more and more muscle by keeping the worst at bay of anything that the strengthening PV throws our way, even as far out as Day 10.

The Ecm may not disagree with the GEFs 11-15 day range after all.

Edited November 20, 2015 by Newberryone

[Duane S.]

Interesting...one for experts..could the SH become a hindrance to uk cold holding the vortex in a place to just deliver +NAO stormy Dec weather?

I think a very +NAO is fairly likely now going through at least the first week of December, probably 2. Something inbetween a more easterly progression of the vortex scenario with very wet windy conditions for us and the SH edging west (but just out of reach), keeping us in a no mans land scenario.

Thereafter up for grabs I would say. I could see the next phase being energy diving SE with very disturbed weather for us and some welcome snow over the Alps in time for Xmas (topping up on the great dumping they are about to receive). Then I think comes our window of opportunity. I think by then we will be watching a significant wave1 event and waiting to see what it will mean for us heading towards the end of the month. As somebody posted earlier, I think we are going to have to endure the pain to get the gain.

Edited November 20, 2015 by s4lancia

[Paul]

You may have spotted the model thread has a new home in the winter thread. More info here (please don't comment in here about this - please use the thread linked below if you want to ask questions or have any feedback)

 

https://forum.netweather.tv/topic/84480-whoa-where-did-the-model-thread-go/

[bobbydog]

Some very disturbed charts again this evening showing the UK coming under heavy attack from the Atlantic as the vortex sets up shop to our north, looking very unsettled and stormy going forward. We could be getting through the storm alphabet at a fair old rate, with the possibility of some notable weather if the models are onto the right pattern for the last week of autumn. 

 

I might be wrong but you may find that Siberian high could actually turn out to be a hindrance in the long run... Not sure though, might be barking up the wrong tree it's just I seem to remember from a previous year where people wanted it to disappear? Maybe someone could put me right...

nope- a strong siberian high promotes colder winters over many areas of the northern hemisphere, including europe. of course it depends on a few other factors but its good news for the winter as a whole.

strong el nino + strong siberian high = ripe SSW conditions i believe...

[Summer Sun]

This evening's ECM ens shows the last of the cold air moving away from the SE during Monday

 

 

By Tuesday we're all back in the less cold air

 

 

Wednesday, Thursday and Friday could be the mildest days of next week

 

 

After this temps are likely to hover around or slightly below average

 

 

Fairly unsettled throughout with some strong winds at times more so for the north and north west its here where we'll see the wettest conditions, though everywhere is likely to see some rain at times, though in the south and south east some longer drier spells are likely if we get any clear skies overnight frosts are likely

[knocker]

The NOAA 8-14 is pretty close to the ecm at T336

 

[Singularity]

This move has upset my bookmark   

 

The ECM det. is very much against raising heights in the Svalbard area beyond +144 but otherwise plays reasonably nice with the Siberian High in that it's allowed to send a ridge up toward the pole to mess with the polar vortex at the trop. level, while interactions with Pacific storm systems look alright for the strat. wave breaking.

 

I do think any direct impacts from the Siberian High will be a real bonus this side of New Years Day but if the high turns out as expansive to the west of Siberia as the GFS 12z det. has it, then the potential will certainly be there.

 

In the meantime, it's becoming apparent that the worst of the wind associated with the storms next week will probably give the UK a miss for the first four days of next week as the lows pass to the north of the UK - though it's a close call for NW Scotland on Tuesday. After that, the storms start to track further south again but the worst effects do look to remain across northern parts at least in terms of the winds. The rain aspect could end up being more of an issue further south, as frontal systems come up against increasingly high pressure across NW and Central Europe, becoming both both tilted (angled more SW to NE than S to N) and slow moving.

 

That said, the extent of those European height rises could easily be adjusted either up or down over the next few days, so stormy conditions could well push further south or wind up missing most of us to the north.

 

There was a mighty storm across the U.S. a couple of days ago and I do wonder if the unusually high subtropical SSTs coupled with nearer or below average SSTs west of the UK might give rise to similar systems in our vicinity before too long. ECM has produced an intense system at some point on 3 of the last 4 det. runs, the 12z of today featuring an absolute monster grazing the north coast of Scandinavia at +240 hours. Trying to estimate the peak winds from the isobars is impeded by how closely packed they are - I just end up with sustained speeds of over 100 mph 

 

The low grazes Scotland as it races over so I imagine there's a short period around midnight Monday with some ferocious winds affecting the far north. Like Abigail but even more vigorous.

 

Edited November 20, 2015 by Singularity

[bobbydog]

But when...Surely a +NAO in Dec waiting for a six weeks into Jan to me suggests a poor first to middle Winter...sorry but surely Winters Past haven't all relied on SSW .....that would be crackers.

many winters have. some of the best have. anyway, an SSW often takes as little as 2 weeks to have a major impact. the clue is in the title- 'SUDDEN stratospheric warming'...

[phil nw.]

nope- a strong siberian high promotes colder winters over many areas of the northern hemisphere, including europe. of course it depends on a few other factors but its good news for the winter as a whole.

strong el nino + strong siberian high = ripe SSW conditions i believe...

The Siberian High can be a frustrating beast though.

 

I can recall too many Winters when he looks as if he is heading west but the strong vortex usually around Greenland holds him back. The boundary of the cold air remaining on the other side of the North sea.

It seems easterlies from a strong westward extended SH are rare occurrences these days but they often give really low temperatures.

However this pattern is always under attack from the jet as it fighting against the PV to it's west usually around E.Canada/W.Greenland.

 

If the SH remains out of reach then we continue to see trough disruption across the UK or just to our east leaving us under the Atlantic influences and milder temperatures.This pattern can hold for weeks and has often brought the cry for it to be removed and for a change of pattern.

 

This is often why Greenland heights are a better solution for cold  as by inference the vortex to our north has been split or displaced to the other side of the pole.

The Atlantic jet is blocked and forced way south allowing the Arctic cold to flood innto NW Europe and the UK ala  Nov-Dec.2010.

 

I agree re.Cohen's theory wrt the SH but wave action doesn't always break the vortex down and this early in the season the PV is coming to it's strongest.This is something that is more likely to materialise later on.

Edited November 20, 2015 by phil nw.

[chionomaniac]

But when...Surely a +NAO in Dec waiting for a six weeks into Jan to me suggests a poor first to middle Winter...sorry but surely Winters Past haven't all relied on SSW .....that would be crackers.

Conversely, can you show me a period of when a -ve NAO that has occurred when there has been a corresponding period of stratospheric vortex intensification (VI) without that period of VI being broken down first? SSW is the extreme of strat warming, but then an extremely cold and strong stratospheric vortex gives a very reliable and increased probability of a strong tropospheric polar vortex and that relationship can't be ignored. Since I have followed the strat in 2008 there have been NO instances of VI that have led to -ve NAO spells without that VI being broken down first. 

 

So, the hunt this winter for snow lovers is for tropospheric precursors to strat disruption to assist the hunt for cold - otherwise the best we shall get is the odd toppler.

[bobbydog]

The Siberian High can be a frustrating beast though.

 

I can recall too many Winters when he looks as if he is heading west but the strong vortex usually around Greenland holds him back. The boundary of the cold air remaining on the other side of the North sea.

It seems easterlies from a strong westward extended SH are rare occurrences these days but they often give really low temperatures.

However this pattern is always under attack from the jet as it fighting against the PV to it's west usually around E.Canada/W.Greenland.

 

If the SH remains out of reach then we continue to see trough disruption across the UK or just to our east leaving us under the Atlantic influences and milder temperatures.This pattern can hold for weeks and has often brought the cry for it to be removed and for a change of pattern.

 

This is often why Greenland heights are a better solution for cold  as by inference the vortex to our north has been split or displaced to the other side of the pole.

The Atlantic jet is blocked and forced way south allowing the Arctic cold to flood innto NW Europe and the UK ala  Nov-Dec.2010.

 

I agree re.Cohen's theory wrt the SH but wave action doesn't always break the vortex down and this early in the season the PV is coming to it's strongest.This is something that is more likely to materialise later on.

don't be having a little wee on my fireworks there phil i'm trying to be optimistic! anyway, my point was, which actually agrees with your last point, it could well be a 'back end' winter. in fact, cohens study finds that in the siberian high scenario this is more likely. also some of the 'best' winters have been in the second half or even february (1947 or 1991 as a couple of examples). anyway, this winter seems unique (as they all are really) so we will have to wait and see. i've got a good feeling about this one though

[chionomaniac]

1946' 63' 78' 87' 91,.....were they all SSW chino...?...not every cold spell is after an SSW ....yes SSW increases the chances but hey what if this Siberian high due to snow extent causes a Scandinavia high with no SSW an we see an easterly...who knows eh

I am aware of that and I am not talking about SSW. I am talking about trop HL blocking following a period of stratospheric polar vortex intensification - can you see the difference and distinction here?

 

PS the years you choose demonstrate this point that I make - check here for the later ones  (no VI present) 

 

http://acdb-ext.gsfc.nasa.gov/Data_services/met/metdata/annual/merra/u60n_10_1978_merra.pdf

Edited November 20, 2015 by chionomaniac

[Nick F]

 

I do think any direct impacts from the Siberian High will be a real bonus this side of New Years Day but if the high turns out as expansive to the west of Siberia as the GFS 12z det. has it, then the potential will certainly be there.

FWIW the 32day ECM EPS weekly control run was showing a pronounced punch toward the pole from the Siberian high out in FI depths of mid-December along with a positive height anomaly over Scandinavia too. This is reflected by the AO and NAO dropping into -ve territory from mid-Dec on the control. Of course, much water to flow under the bridge before then, with a +ve AO and NAO the overriding signal into early Dec, but the persistent Siberian high anomaly showing into the extended range could just tip the balance enough to bring a pattern change even before the New Year.

[Ali1977]

FWIW the 32day ECM EPS weekly control run was showing a pronounced punch toward the pole from the Siberian high out in FI depths of mid-December along with a positive height anomaly over Scandinavia too. This is reflected by the AO and NAO dropping into -ve territory from mid-Dec on the control. Of course, much water to flow under the bridge before then, with a +ve AO and NAO the overriding signal into early Dec, but the persistent Siberian high anomaly showing into the extended range could just tip the balance enough to bring a pattern change even before the New Year.

This is good news (potentially) let's hope after the last 2 years we have another classic winter.

[Mucka]

Mucka if you took UKMO at face value im not 100% sure it would be overrun-

 

Looks like a bit of disruption there- possibly enough to force an undercut-

 

S

 

Hi Steve,

I'm sure there would be dsiruption and some undercut but looking across the output the forcing looks quite strong from deep trough development  S Greenland with jet powering up so UKMO looks to be underdoing that.

Taking the 144h  chart on face value though I still think the patttern would be a little too far East to get a continental flow and even then forming high pressure would be under further strong Atlantic attack.

Hard to see how could it build West under those circunsnaces without the models being very wrong upstream.

Granted once you get undercut the pendulum can start swinging back the other way.

All hypothetical I guess without seing UKMO 168/192 

 

At least it gives us something to cling on to but I think we need to see further improvements on UKMO even to hope for a continental flow from anything other than a transient flow circulting around a diving low and ECM, GFS, JMA all need to be onboard yet - so a long shot in the dark for now?

Edited November 20, 2015 by Mucka

[Cloud 10]

Some good old fashioned cold zoniality from the 12z JMA this evening.

 

[chionomaniac]

Thank you an yes..coupling Trop vortex with a strong strat vortex will mean a struggle to see any hlb...hope I'm learning....but think I'm understanding?....and with west zonal winds strong strat vortex an lag will be hard to dislodge the organised vortex..that's a lay mans attempt chino ...however the Siberian high is a joker in the pack?

Hence why we want to keep an eye on tropospheric precursers to strat disruption.

 

The Siberian high is a great starting point to this in an EN winter but so is the EN DEC pattern suggested in the 2-3week timeframe

[Yarmy]

The coldest December in the CET record (1890) had a +NAO. Not that I think anything like that is remotely on the cards: the output is shouting zonal, unsettled and average for some time. Those long rangers that had a slightly below average UK and above average western Europe for December don't look too far from the truth.