Model output discussion - 5th December 2016 - Into Winter we go

[fergieweather]

34 minutes ago, Mucka said:

Between a rock and a hard place but if there is necessary ambiguity in the forecast can people be blamed for misinterpreting it? 

For me the first half of the 30 day outlook is fairly clear, no chance of cold really with SW/W flow and high pressure SE, but the second half is very suggestive of the Atlantic trough being further South and high pressure being oriented further NW than the first period (not to our NW) with the battleground between colder and warmer air being over the UK and although we do get the caveat that orientation of the battleground will dictate conditions it is also suggested unsettled weather will be more likely to the W (not NW) and colder weather to the E (not just drier SE)

It is actually very well written  but I wouldn't blame anyone for interpreting it as being better for snow prospects than may actually be the intention.

Until long range forecasting becomes more accurate and reliable or the MetO decide  to shed their professional skins and go all Daily Express on us, I'm afraid the situation won't change.

What I do credit the MetO with is their lack of pretense and the integrity they display with regard to current long range forecasting capabilities and having people within the organization actually post to this forum is very much appreciated - even if we do shoot the messenger on occasion.

 

Personally, I would say blocking chances as the y relate to cold and snow possibilities are slowly being pushed away, there is very little talk now of Atlantic ridges or high pressure to our NW. Christmas is just beyond two weeks away so still enough uncertainty for hope of a turnaround but we need to see a cold signal proper appear within the ensembles soon to see any snow over the Christmas period. 

 

A good summary of the present situation, Mucka. They're conscious of the potential for (even fairly nuanced) changes to broadscale set-up to have quite marked impact in terms of UK weather type and temperatures. As you note, rock & hard place sums-up the difficulty well and none of it aided by erratic performance lately in EC Monthly output and another fickle/ambiguous run from it yesterday. History tells us that these scenarios manifest when the model is toying with two opposing outcomes at longer leads: given differences with GloSea5 (and for that matter, ditto lately between GFS & EC operational suites), it's perhaps unsurprising. 

The very bad luck for M-R forecast desks is this mess all focuses into Christmas period. Had this all been for late Nov prognoses, nobody would be paying much attention...!

[snow freak]

5 hours ago, tight isobar said:

Lol.

You just have to laugh really. 

A large swath' of Europe has the freezer door open on it. While we sit in the triangle of' nothingness! 

Its looking atm' like a stagnant situ with at best some minor inflow of continental air at times....

However still some resolve' perhaps of better synoptics' going forwards. 

are you really surprised, we, in the UK have been stuck in a perpetual Autumn now for the past few years (both in summer and winter alike).

[Methuselah]

I wonder what jolly japes this afternoon's 12Z will play on us all? A stonking (there on the 12Z, gone on the 18) Christmas Day blizzard wouldn't surprise me at all!

There's no gain without pain!

[nick sussex]

Oh dear could be some drama on the GFS with a Scandi high if the shortwave behaves itself!

[gottolovethisweather]

On 05/12/2016 at 19:04, gottolovethisweather said:

Bear in mind, my watch period was and still covers the period between the 10th and 13th December, which should see a relatively small yet still significant pattern change after three or four days of unseasonal warmth by day and night.

Why am I so confident in this being a crucial timeframe, well because it has been showing hints of it across all model suites (particularly the 0z and 12z suites) for a number of days now. Additionally, take a gander at the GEFS ensembles spreads which further back up my suspicions of a pattern change of sorts.  

 

 

 

 

 

 

 

 

 

 

 

 

 

Well, the above quotes my post from Monday and in Meteorology five days is a long time. When you think of all surface developments and Upper airstream changes which can take place during 120 hours and the difference it makes to the tiny island of the UK's weather, and you'll get my point. During this past week, however, it had felt more like five entire GFS operational runs had already taken place before we got to the present date, yes we are simply five days on. We are, but only nine days into Meteorological winter and whilst there has been a lack of deep cold and snow (relatively rare UK phenomena), I have had more Air Frosts and foggy interludes than the whole of December and January 2015/16 combined. This latter fact pleases me no end, despite us being currently bathed in relative warmth. Where am I going with this? Well, please revisit the quoted text above and perhaps the whole post as most things have subsequently developed as expected, and post the 13th December I remain convinced a change is afoot. Something with a colder orientation and who knows, the word "wintry showers" might start popping up in mid-term forecasts before long.  It's no certainty I'm correct of course or even whether the experts are, with regards the mid-term, with tomorrow becoming a potential wet day down in Southern England, ask yourself how many Model Outputs had that surface feature development on their radars (at D3-D5 this Monday gone)? The weather and more appropriately Mother Nature can and does a mug of us all, time and time again.

Another word to the wise is that I am more taken in by the guys who know their "stratospheric processes" and our well-known experts at the heart of forecasting than by people attempting to make their assumptions based on one run alone. I say this as someone whose been around netweather towers for nigh on ten years now so I certainly don't lack posting experience. Please do take time before posting your thoughts, follow those few who've earned your respect. As in life itself, please live a little, listen and learn from what others have to say. I will hopefully return later tonight with my latest thoughts after having taken on board all of this afternoon's and evening's model outputs. 

Edited December 9, 2016 by gottolovethisweather

[Singularity]

MJO means are out. GEFS steadfast in a quick (by a week's time!) change to Pacific dominance, UKMET similar, JMA rocketing along and ECM... drifting about aimlessly.

What gives, ECM? Tempted to entirely throw the det. and ens. out of the window until it falls in line with the others tropical-wise, as now three major models and numerous experts in the field would have to have the wrong idea in order for ECM to be anywhere near close to the mark.

I can only imagine ECM is seeing something going on on the IO/Maritime Continent side, could there possibly be even further interference? That'll be upsetting the momentum transports and everything, leaving us at the mercy of a zonal flow.

 

So if we chuck ECM aside (so rarely done that I can't believe I'm saying it), we have a general picture of amplification in the Atlantic sector increasing in the 10-16 day period. Recent GFS runs have resolved this into a massive Atlantic trough with the UK on the eastern periphery - similar to Nov 2009 but perhaps with a bit more HP influence this time around - but any overestimation of the jet stream intensity around that feature will open the door to a drier and colder outcome.

Before all that, the pulse of activity in the eastern IO seems to have been dropped for the most part. That corresponded with a mid-lat block in our vicinity so we've lost some support for getting that in place next week, though typical model oversights could still allow the ridge to take more control if trough disruption occurs sufficiently.

It does feel like every opportunity to get something more seasonal has to fight for dear life to actually transpire this month. Unfortunately when you have a disrupted vortex state, you get super-mild regimes as well as cold ones. What we're seeing at the moment is pretty exceptional in terms of how high the temperatures are reaching, especially where that's coupled with a lot of dry conditions in The Southeast.

[Matthew.]

50 minutes ago, abbie123 said:

Christmas Day anyone.

That's a proper Victorian Siberian flow Looks like Feb 1890.

[Carl46Wrexham]

51 minutes ago, abbie123 said:

Christmas Day anyone.

BANK...stick yer pattern reset with its resultant weeks of raging zonal crud where the sun don't shine.

 

[Singularity]

 

Well, for those still into the run-by-run approach, we have a significantly sharper trough digging down west of the Sceuro High and a slight but still useful reduction in the pace of the low swinging into the broad trough to our NW.

[Singularity]

06z:  12z:    

Let's face it, it's truly terribly timing for a deep low to turn up in the Atlantic. We do, though, have the blocking closer to our east and no tiny shortwave running over it on this run.

One day it's got to work out well... right?

After all just look at this jet profile; if the block held its ground much longer, the lack of another trough immediately west of the one south of Greenland means the block likely gets reinforced and extends west a bit. We've seen evidence of that in some recent runs, but then another trough does book it out of the U.S., tilting the jet back to the NE and making a mess of things.

I'm not sure if we can possibly see the midweek trough adjusted west and/or toned down enough to allow the block to fend that subsequent Atlantic 'surge' off. It's a real shame in that respect not to have some tropical forcing at work in the 6-8 day range, as that would likely delay that next trough and allow the blocking high to get right across the UK.

As it is, I'm glad GFS has at least made some effort to get a chilly continental flow back in as we pass the mid-month point.

Edited December 9, 2016 by Singularity

[Ravelin]

Lower heights over the Med on this run at least...

[Ali1977]

On 09/12/2016 at 16:29, Ravelin said:

Lower heights over the Med on this run at least...

True, but look at that PV again, going to need a miracle to migrate the high North and disrupt it

[Ravelin]

8 minutes ago, Singularity said:

Let's face it, it's truly terribly timing for a deep low to turn up in the Atlantic.

It is the GFS though, which has historically had a tendency to pump up lows, then tone them down later hasn't it?

[carinthian]

Stop there at 168t . GFS similar to earlier extended UKMO Atlantic charts . Atlantic really struggling against the block. Surface wind flow should start to back across much of England and Wales. We need to still see heights falling over Biscay and recent runs still continue to show that. C

Edited December 9, 2016 by carinthian

[cheshire snow]

At least on this run temperatures return to normal later next week with overnight

Frosts,will settle for a nice frosty Christmas .

C.S

[Singularity]

Just now, Ravelin said:

It is the GFS though, which has historically had a tendency to pump up lows, then tone them down later hasn't it?

Any model bias toward over-responding to the tight thermal gradient in terms of LP development could turn out to be critical if we get some runs showing us right in the balance.

 

This run still has that cold undercut from the east edging westward... the train might stop pretty short of the UK this time.

What particularly interests me is the 'wrap around' of the jet through Scandinavia, which is more pronounced on this run and something GP mentioned with respect to us potentially toying with an easterly flow ahead of the major pattern shake-up once the 6-7 or 7-8 MJO activity takes effect.

 

[gottolovethisweather]

6 minutes ago, Ali1977 said:

True, but look at that PV again, going to need a miracle to migrate the high North and disrupt it

A Scandi High isn't such a long shot though, today's UKMO is toying with that prior to the mid-range yet FI chart posted by Ravelin. Eight days away, in fact.

Edited December 9, 2016 by gottolovethisweather

[Singularity]

1 minute ago, carinthian said:

Stop there at 168t . GFS similar to earlier extended UKMO Atlantic charts . Atlantic really struggling against the block. Surface wind flow should start to back across much of England and Wales. We need to still see heights falling over Biscay and recent runs still continue to show that. C

One has to wonder whether that long, smooth arc of extreme jet stream winds is just too simplistic/presumptuous.

I'm getting way too far into this run now... can't resist the will it/won't it moments 

[Ali1977]

On 09/12/2016 at 16:37, gottolovethisweather said:

A Scandi High isn't such a long shot though, today's UKMO is toying with that prior to the mid-range yet FI chart posted above.

If the high towards Scandy can hold and create a proper Scady high that would be a minor miracle, is that really where we should be looking "if" we can get something colder? Let's see how many ENS can do it, if any

[Ravelin]

Anyone ever seen a low come up from the Med before?

[Singularity]

  

If we had a better block in place and better amplification being forced upstream, even the mightiest of lows could be torn apart and some of it sent crawling under our block.

GFS 12z really powering up the tropospheric vortex now - but with a lack of lower-mid stratospheric support it shouldn't be able to sustain that for long. The big east-U.S. ridge is of some interest.

[gottolovethisweather]

4 minutes ago, carinthian said:

Stop there at 168t . GFS similar to earlier extended UKMO Atlantic charts . Atlantic really struggling against the block. Surface wind flow should start to back across much of England and Wales. We need to still see heights falling over Biscay and recent runs still continue to show that. C

 

The voice of reason, Thanks, Carinthian. The question is, is this the new favourite in our model output race of many runners? Sometimes, it's best to get your money on a second or third favourite in such races circumstances. There are no certainties in any of our computer generated pieces of meteorological guesswork, it is only as good as the data fed into in the beginning. And whilst I wouldn't mind betting tomorrow's little low feature might yet curtail some of our forecaster's projections, next week is ultimately more forecastable with heights rising to the North and East of the UK and a very slow trend downwards in terms of Temperatures from their currently exceptional highs.

[carinthian]

4 minutes ago, Singularity said:

One has to wonder whether that long, smooth arc of extreme jet stream winds is just too simplistic/presumptuous.

I'm getting way too far into this run now... can't resist the will it/won't it moments 

At Singularity, best look no further than 168t and that's for me the most extended range for me anyway. 

 C

[bluearmy]

Does anyone fancy digging out the gfs op strat zonal flow forecast to see if it has a disconnect with the strengthening upper strat- could be a reason why the ops are so strong on the trop vortex development 

woukd also be worth seeing if the gefs are similar as they seem to manage a lot more amplification hemispherially 

[phil nw.]

An interesting little battle commencing with the Atlantic jet having to ride up against the building heights to the ne by day 4.

We are starting to see falling heights across the continent too which would reduce any sinking of the high and help to bring in a south easterly off a cold Europe whilst it's there.

This would fit in with the falling temperatures that gefs have consistently shown towards Christmas week.

We just need the ECM to get the Christmas feel and fall in line.