Model output discussion - 1st December onwards

[johnholmes]

5 minutes ago, Mucka said:

 

I'm not sure there were any posts suggesting GFS would bring snow to low land England John, just that it was an improvement over its previous output in hi res and move toward the Euros.

Where did I make that suggestion please Mucka? I have posted with a link for folk to look at a series of charts and made a comment from my point of view not posting that there has been, I quote you above?

[Froze were the Days]

Little improvement at 120z on ecm - little undercutting...just looks like rain to me with LP to the west.

[nick sussex]

Part of the reason for the differences is you guessed it the upstream pattern! The UKMO is most amplified over the ne USA, the ECM next then the GFS the flattest solution. This effects the movement of the PV and the energy release from the troughing to the nw.

You can correlate how far south the cold gets across the Canadian/USA border at T120hrs with the pattern over the UK in terms of favourable or less so. More cold heading south across that border the PV pulled further west.

 

Edited December 29, 2015 by nick sussex

[BLAST FROM THE PAST]

 

Upgrade alert??

 

BFTP

[Mucka]

6 minutes ago, johnholmes said:

Where did I make that suggestion please Mucka? I have posted with a link for folk to look at a series of charts and made a comment from my point of view not posting that there has been, I quote you above?

I didn't say you did either.

It is just your posts suggests you think there are some controversial posts re GFS output.

"I would be very grateful if one of you bright chappies/chappesses could give me a BRIEF outline of where we are. Reading some comments above it might well help some of our newcomers and visitors as well"

 

"

"how about IF it will allow me to show Extra 850 mb Temperatures and isobars (the white lines) folk make up their own minds?

I hope this can be allowed please Paul/team, just this once.

It might help visitors/new folk see what the latest GFS is suggesting?

My own view is that no sooner does it bring in lower 850 temperatures than the next surface system swings in with less cold air. Through most of its run it shows the isobars are from west to south west, rarely north west, so snow prospects away from hills and the far north look slight to me. Probably non existent for any lasting/lying variety, although the Scottish ski resorts should do quite well"

 

I had enough of the twilight zone the other day so please carry on.

Edited December 29, 2015 by Mucka

[Liam J]

A blast of PM air from the west at day 3 on the ECM which would likely give snow to high ground with -4/-5c 850's but the deep cold way to the NE of the UK, Shetland looks like the place to be! Very cold air spilling out into the Atlantic across the pond. 

 

[Froze were the Days]

ECM marginally better at 168z but we are talking miniscule differences from 0z with perhaps a bit better negative tilt to the LP with the core slightly further south but still the real cold air to the north/north east of Scotland.

[MR EXTREMES]

2 hours ago, knocker said:

Impressive number of lows on a strong jet.

Abandon hope all ye who enter here

Indeed heading towards real winter now buckled jet and separated low and heights showing first stages Greenland both gfs and ukmo have different ideas how to get heights into Greenland great models for a fair number of days now

[Froze were the Days]

Fairly similar as per this mornings ecm run...pear shaped at 192z

[Mucka]

JMA improves over previous output but not quite there.

That leaves UKMO at one extreme and GFS at the other with JMA and ECM somewhere in the middle.

Have to admit the ECM is disappointing tonight - we can hope it is very much on the mild side of its ensembles by day 8/9

Place your bets please.

Edited December 29, 2015 by Mucka

[Polar Maritime]

3 minutes ago, Greenland1080 said:

Isn't this exactly what Glacier Point mentioned for early Jan?......PM air source from West North West with potential as we head into Jan...seems right to me at moment...

 

As heights push West towards Greenland this in-turn would bring a N/W flow.

Edited December 29, 2015 by Polar Maritime

[Eskimo]

I'd like to point that out that, yes, the ECM is still showing an active Atlantic with Polar Maritime air being the form horse in the latter stages. However, there's plenty of scope for reloads down the line. 

[phil nw.]

Just for illustration purposes for anyone new to the charts below the ECM T168 pressure,850hPa temps.and windflow charts

the Atlantic trough /belt of low pressure strung across the UK.To the north of this winds from a colder easterly direction where the cold air is.However for much of the UK less cold,although feeling much colder than our weather of recent weeks so rain for most of us.The N.Isles and far north of Scotland,highlands etc could see quite a bit of snow if that verified though.

This is really just to show that currently the whole setup is modeled just too far north to see widespread cold from that cold pool to the north east.

 

 

[terrier]

So not a great ecm tonight which seems to move slightly towards the gfs outcome. I think we will see a half way house situation here. From mild rain to cold rain not a great outlook for us here in the north with more floods looking likely. 

[booferking]

Disappointed with ECM cold rain instead of mild rain don,t want at all to be honest need them lows further south like the ukmo at 144 then we might have a chance.

 

[Geordiesnow]

I have to admit, won't it be ironic if for all the blocking, the UK does not see any significant cold and that is a real possibility at the moment, I think you can have too much blocking and to be honest, the signal does seem to be moving height rises from Scandi into Western parts of Russia and for Atlantic lows not really undercutting all that well. 

That said, its a volatile output at this moment and any details in the medium term are definately subject to change. Lots of potential though. 

[Frosty.]

Well I see wintry potential on the horizon, at least for the NE, thus far this season there has been nothing at all for coldies to grasp on to, just relentless blowtorch mildness but now there is and a bit of tweaking on today's models would show a much colder shock to the system, indeed the ukmo and gem already show that!.. its not over, indeed it's just beginning.

[karlos1983]

Question- do we pay more attention to the GFS or Parallel ?

Edited December 29, 2015 by karlos1983

[Tamara]

I spoke during November of (disputable) connects between predominantly -ve AO July's and the state of the polar field the following January - giving reasoning in terms of seasonal and sub seasonal phenomena feedbacks as to how and why this can occur, and why it might (or might not) occur this winter - following the -ve AO signature of last July. An especially complex equation to fathom, bearing in mind the competing quite extreme drivers at work increasingly through the second half of 2015 and which are reaching a peak this winter.

Then , back in summer 2015, we saw sudden surging of atmospheric angular momentum tendency on the back of high amplitude tropical/extra tropical coupling imprinting the strengthening ENSO signal, and, 6 months later we are set to see a similar sequence of atmospheric engagement at high amplitude, that, as only one part of the jigsaw, is looking increasingly likely set to turn the modality of the pressure pattern over the polar field completely upside down.

Leading up to this, as we know, has been much less interesting and anticipatory. November into December 2015 saw a lagged Nino atmospheric response due to tropical convective noise over the Indian Ocean which dampened down the westerly wind anomaly responses across the Pacific. A wave train arcing across the US, during that time has extended warmth further north into Canada than a traditional Nino composite would suggest - alongside a w/QBO enhanced contracted and strong polar vortex. This skewed pattern destructively interfered with the natural processes of Nino Rossby wave breaking actions on the stratosphere that can lead on to weakening of the vortex thereafter. This seqeunce, therefore, augmented the VI (vortex intensification) period that chiono and Lorenzo have regularly been watching over so far this season in terms of actual strength of intensity attained, and when it might be deemed to come to an end. That time has duly appeared.

At the same time however, faith in Cohen's expected representations of polar sea ice concentration feedbacks has been well repaid. Enter the 'Kara High' as we close the year. Something of an ocean/atmosphere coupling enigma may have persisted through late autumn and into early winter, but so are we seeing something of an enigma unfold over the Siberian polar field as the w/QBO driven upper vortex comes up against a mightily strong opposite negative feedback - damaging it from the bottom upwards.

The timing of this pressure rise development is coinciding with tropical forcing becoming much more favourably aligned with the base ocean ENSO state. In simple terms, tropical forcing has been moving eastward, in line with early suggestions (and also obliging to hopes) and the implications of this in terms of re-surgent AAM and resultant ampification feedbacks into the stratosphere have become large based on the pot of Pacific water still bubbling away nicely at well over 80F.

Furthermore, with warm air advection also having been pressed hard into the Canadian Arctic, due to the skewed upstream pattern (Canadian Warming?) could we be about to reap rewards of sitting out the endurances of the last 6 weeks turbo charged tropical maritime pattern?

The suggestion of combined tropical/extra tropical forcing creating the same surging AAM tendency that was seen in the summer to tip upside down the polar profile in July has appeared on cue to mirror that possible parallel -ve AO correlation this following January. Destabilising warm air advection both sides of the pole firmly underpins the longer range model insight from the METO in terms of the further outlook and resultant cross polar ridging, irrespective of whether or not that leads us and NW Europe to a cold pattern.

The current modelling though is just the first part of that change of increasingly indicated modality changing process. A good reason, in my opinion at least, not to agonise too much over intra day modelling differences over the heights to the NE and undercut potential in the shorter/medium term.

Its time to trust in the new trend being the new found friend I think.

The effectiveness of this passage of sustained vortex attack is important in terms of how long it manages to sustain itself. Positive Frictional and Mountain torques will keep AAM bubbling, and will ensure wave activity attack is sustained well into January. With a clear pathway to the NE and Cohen feebacks established, I would be highly sceptical of any longer range numerical model indications of this vanishing into ether later in January. Polar feedbacks of this type, under the unstable and unprecented sea ice patterns we see these 21st Century years establish seasonal amplification patterns which have a powerful momentum of their own that do not stop intra seasonally without very good reason. Last winter we will remember that the feedbacks favoured the other side of the pole - with the Kara/Barents unfavorable for wave activity flux. This year though, superimpose favourable WAF with strongly tuned tropical/extra tropical forcing alignment to enhance higher latitude amplification potential, and the timing for switch of the Annular Mode could clearly be critical in terms of how the rest of the winter plays out. Its happening exactly when it needed to in terms of any crossroads between staying with a strongly w/QBO driven +ve AO vortex or a flip to spectacular destruction of the spinning top to a defintively -ve state.

The MJO cycle will, eventually, return to the Indian Ocean and this would represent another attempted El Nino 'wane' period, such as we saw in November. It would also mark a drop back, when it comes, in relative AAM tendency and hence also a drop back of poleward directed amplification wave damage potential on the vortex. Furthermore, as stated in previous posts, it would come increasingly at a time towards later winter when the global atmospheric circulation becomes more and more resistant to poleward propagating of the Nino westerly wind anomalies that can create polar heights amplification under a -ve AO (as opposed to the downsteam zonal Euro High responses as we have seen thus far under a Nino influenced strongly +ve AO regime).

Therefore the coming few weeks are maximum damage exploitation time, but current indications are that both atmosphere/ocean forcing and troposphere/stratosphere forcing are coming good together at just the time that previous posts have suggested would be required. The effects on the AO and the stratospheric vortex could be noteworthy indeed, and who knows where we end up in the UK and Europe with a pincer destabilisation movement from both sides of the pole.

Best case scenario for cold weather watchers: Heights heading to our NW, following the upcoming phase of trough disruption against the Kara High could be the next stage, as discussed in detail already over the last day or so - this in turn creating ridge link up to the NE height anomaly, and cut off low pressure to a southern stream as the NAO flips -ve and the vortex is smashed from both sides of the pole.

Less favourable scenario for cold weather watchers: . Instead of higher latitude ridge link-up, a transfer of jet energy northwards as relative AAM tendency drops through renewed Indian Ocean convection and interferes with the amplification feedback process during a period of vortex weakness - thereby allowing the vortex to re-group, sinking any attempted higher latitude block back towards the UK and Europe. In terms of seasonal wavelengths and any such vortex regrouping not being on the scale of late autumn and early winter, this scenario would still likely be much drier than the first half of the winter, which is a god-send in itself, but not the cold wintry flavour anticipated and hoped for on much of this forum.

Lots more to watch out for before even contemplating such eventual scenarios though

[nick sussex]

After the ECM which seems to have harpooned the festive spirit I think there are several issues that still need resolving before people reach for the Prozac.

As I alluded to earlier there are some key differences as early as T120hrs, the amplitude of the pattern over the ne USA. What on the face of it seems small change on a global scale makes a big difference to how the pattern develops. So here are  the T120hrs firstly the UKMO:

Note the dig of colder air into the ne of the USA.

Now the GFS T120hrs:

You can see the difference over the ne USA aswell as the PV more organised to the nw of Greenland:

Now onto the ECM

As you can see not quite as amplified as the UKMO but more so than the GFS, you can correlate the dig south of the cold air in the ne USA with the orientation and dig se of the low near the UK. You'll also note that gap on the UKMO between the UK low and shortwave upstream.

After this the UKMO runs that shortwave in western Alaska into a chunk of the PV in nw Greenland, this phasing pulls the PV into a more favourable location at T144hrs.

Theres a lot going on upstream and the complexities of the evolution mean that there are likely to be more changes, when you're dealing with relatively narrow differences on a global scale but for the UK mean the difference between rain and snow I'd be cautious in viewing tonights outputs as giving the correct solution.

I'll see what the NCEP State forecasters have to say re the upstream pattern in terms of model preferences especially for that key ne USA area, hopefully that will direct us into the more likelier evolution over there.

 

[Captain Shortwave]

ECM day 8-10

GFS for the same time

 

Maybe Fergie has a point about the GFS being "less progressive", some people had to bring it up. 

On a more serious note, I must admit that surely the ECM has to be over doing things in terms of the loss of high pressure over our side of the pole, it does seem out of kilter with the other runs and anomalies, even if other runs don't deliver much in the way of cold and snow.

In terms of anomalies the GEFs are interesting

There is certainly an suggestion of increased interest around mid month with some kind of block of higher heights developing in the northern Atlantic with a trough to our east. Watch this space, before then the will it/won't story of the complex Euro/Atlantic pattern will continue with the risk of a lot of rain (or snow if you are lucky).

Edited December 29, 2015 by Captain Shortwave

[Troubleatmill]

Although ECM doesn't get there, looking at the NH I don't think ive ever seen a split vortex such as this before, totally ripped in two!,  January is going to be full of fun

[nick sussex]

Just in the NCEP MJO update, both good and less good news:

MJO and other subseasonal tropical variability: • The MJO remained coherent and robust, with the enhanced phase now propagating over the west-central Pacific after rapidly crossing the Maritime Continent. 

• Dynamical model MJO index forecasts all support continued eastward propagation of the signal across the Pacific during Week-1. During Week-2, the GFS slows the eastward propagation and amplifies, while the ECMWF depicts the MJO propagating to the Western Hemisphere.  

Extratropics: • The MJO is likely to support a downstream pattern change in the extratropics during the next several weeks, with a transition to positive height anomalies across the Arctic (negative AO). El Niño influence is anticipated to remain prominent as well; however, which may help to counter the MJO response over parts of North America.
 

The good news of course the negative AO, the less good news is some possible countering of the MJO response, you often find quite a battle between the El Nino and the MJO especially when the former is strong. We'll just have to see how this evolves but certainly the negative AO is good news.

[January Snowstorm]

The main story this evening is the relentless storms and rain passing over us (my location on alert tonight)

The first week of Jan looks like more of the same. It would be nice to get some cold and snow but let's not kid ourselves it's not yet on the horizon all the way out to 240hrs

[Man With Beard]

Just come in tonight, clearly the main focus is now on more storms crossing the UK, but snow not favoured by most models - just. 

But looking through the GEFS ensembles destroys any semblance of confidence one might have in the final evolution. By T192, you've got everything going on - flooding, hurricane gusting storms, snow, blizzards, average temperatures, freezing temperatures, westerlies, easterlies, northerlies - it's all there, pick your favourite!!

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=192