Model Output Discussion 29th December - Into mid-Winter.

[knocker]

A quick overview of the GFS this morning for the 10 day period merely confirms a bit of a mixed bag. Some amplification of the Azores and then an abrupt change to zonality This would appear to be caused by a lobe of the vortex falling SE between Greenland and Iceland. Needs to be supported elsewhere before taken too seriously. Anyway some detail in the closer time frame.

The benign weather over the weekend soon gives way the fronts tracking down the country on Monday whilst becoming much windier from the NW which is the order of the day until Thursday. Then the well sign posted amplification gets underway.with the Azores ridging north in the western Atlantic and the uper trough tracking SE across the UK ((the jet is not as strong as it has been as a much slacker thermal gradient). On the surface this triggers a small perturbation in the flow which tracks SE over the north and could well bring snow to the high ground.

From here it gets a bit messy and I'm not sure I would attach too much credence to it but the Azores ridges sharply north over the UK and small depressions are thus forced south to the east

After that the aforementioned lobe comes into play and we are in the zonality region with a strong WNW jet. Best left there, Essentially this evolution does introduce colder Pm air towards to back end end of the period snowfalls would appear to limited to the high ground and the north and mainly falling as showers. But as mentioned I would hesitate to take this at face value from around T168. The ridge only has to be a fraction west to alter the picture somewhat.

Edited January 7, 2017 by knocker

[That ECM]

12 minutes ago, Ali1977 said:

And GFS backtracks, what a surprise. Fri and Sat still look cold in a Northerly though . Lets see what the ECM does, I'll hazard a guess that it too will backtrack from a prolonged cold spell with an Easterly ending 

I wouldn't be so sure about ecm. Ukmo is looking good at t144. Fairly consistent, the gfs is all over the place at the mo imo.

[knocker]

A quick look at the GEFS anomalies this morning finds it has shifted the main lobe of the Canadian vortex,has  positive anomalies in NE North America, a weak trough NW of the UK and a zonal Atlantic.

[Penrith Snow]

The GFS from +200 has a January 1984 look about it with cold zonality and the -5c 850 line south of the U.K., I imagine it would be cold enough for snow showers up north on many days.

Cant be taken seriously at this range but I think the ECM easterly last night was a ghost anyway.

So many options on the table but cross model agreement that next Friday's north westerly will be quite potent, should be able to squeeze a wintry shower out of that mother.

Nothing like Greece however where my Greek friends are complaining of near record cold!

Andy

[NO LONGER POSTING]

Morning gang a snippet taken yesterday from a post of mine in the regional thread before the 18z started rolling out 

"I put £10 on the table that the GFS 18Z smashes the 12z out the water and it's a massive upgrade on cold. Then come 00z it will be watered down again and reapet until the event comes closer and we end up with a half way house."

This is what the GFS is all about it either sinks the ship last minute or it jumps on board just before the ship sails. 

It's nothing unusual the GFS acting like this is, it struggles immensely with the smallest of details such as a short wave or position of a high. 

Its a fantastic model though for trying to pick trends out watching the gfs for the last week, the trend is there for cold and the other models see it too. 

So like I said yesterday let's wait till Wednesday before making rash decisions 

Edited January 7, 2017 by Surrey

[knocker]

The ecm has a little depression that forms in the circulation of the main trough tracking down the North Sea to be just NE of Yarmouth 12z Friday  which may bring some snow showers to the SE otherwise they would appear to be confined to the NW.

[Seasonality]

Pretty consistent from the ECM in its latter stages.

[Polar Maritime]

The GFS continues to show a cold shot from the N/W by the end of next week. With snow chances into the South Midlands and very cold -8/9/10 uppers over the UK it will feel bitter especially in the Northerly wind, Again some 'prone' locations could get a good dump and detail will be worth following..

Into the rest of the run, And the GFS shows repeated cold attacks from the N/W. 

 

 

Edited January 7, 2017 by Polar Maritime

[Seasonality]

Just now, Polar Maritime said:

The GFS continues to show a cold shot from the N/W by the end of next week. With snow chances into the South Midlands and very cold -8/9/10 uppers over the UK it will feel bitter especially in the Northerly wind, Again some 'prone' locations could get a good dump.

Definitely looking good in the reliable. Such wild swings in FI there is even less point than usual worrying about it.

[knocker]

The ecm ends the run by relocating the Canadian vortex west with ridging in NE N. America plus amplification in the Atlantic with a lobe over Greenland and trough with the Azores ridging in the east. Is this paying homage to last night's 10-15 EPS I ask myself

[Mucka]

GFS toying with keeping us in a prolonged PM flow, with occasional warm sectors, with the trough remaining organized as it moves East and the Southerly jet keeping The Azores high displaced and discouraged from ridging back in.

The control run takes this further and maintains cold over the UK for well over a week which would be a phenomenal cold/chilly spell without any blocking and great for snow chances.

As with the 18z the Op and control were among the colder solutions with lot's of spread.

 

I would tear up yesterday's cautious forecast if that were consistently modeled and backed within the ensembles.

ECM continues with last nights theme of building a ridge toward Scandi after a brief Arctic plunge.

 

UKMO is more aligned with ECM than GFS at 144 upstream with a less organized shift East of the trough

Edited January 7, 2017 by Mucka

[IDO]

As expected the ECM op in the reliable takes a big step towards the GFS take on the next week, and GEM catching up as well.

The GFS was what I was expecting during yesterday's 12z run when the PV energy undercut the Greenland "heights" early in the run, the colder upper/NW flow maintained longer. On this run it does that, but there may be fine margins in that scenario? That has always been my take on this, with the window closed now for any prolonged amplification, a flow from the NWW bringing colder zonality to the UK:

Where that cold pool/trough ends up within the Euro region is guesswork at this range.

The ECM D10 chart less amplified than last nights, but probably still over doing it, and although a 33% cluster support on the GEFS (though not as strong) for this play, the GEFS suite has moved on from that on this run, with the Control and op now sending energy SEE:

ECM D10  GFS 

We will see later if this is a trend or not, though the GFS seems to be a step ahead of the rest re changes in the Atlantic sector of late.

With the variance with the pre-D10 pattern within the GEFS, the FI charts are even less useful than normal so probably best not to go there.

That initial cold flow, 13th remains clean, so snow potential to the usual favoured places from a PM shot. The following three days there remains a cold upper air  pattern over areas of the UK so if they are not watered down in the intervening run up, there is always a chance of some snow cropping up in a disturbance.

Before then a milder 5 days as a whole, 2-3c above average highs most days IMBY.

[winterof79]

And without getting at all complicated the majority of the models predict wintry weather at 144Z in winter.UKMO,GFS AND ECM .The conditions in a COLD N/Westerly should not be underestimated.A slack flow sets up at 150z and streamers off the Irish Sea cannot be discounted.

And no there is no easterly

[bluearmy]

Pretty much as expected this morning. The route post the norwester not pinned down and the ridge on yesterday's ops about as good as it gets for us with the more likely outcome what the ECM and gem show this morning with it suppressed further south. 

knocks showed the GEFS 5 day mean earlier and it isn't too dissimilar to the geps. the Atlantic gaining strength as the low anomolies drop further west and south to fill the area the Atlantic high anomolies were situated recently. But the European ones remain on the low side so that envelope could be more nw/se than w/e. Through week 2  I'm still seeing lots of trough disruption against blocking building to our ne. But with the Canadian vortex strong, too much mobility. But it is January and surprises most likely to pop up at this time of year re surface conditions outcomes. IF the upstream forcing ever relaxes then we could see a similar solution to yesterday's 18z (or even better for coldies) but upstream hasn't done us many favours thus far. 

[snowice]

No Easterly that's misleading later stages of ECM is same as yesterday 12z whether it comes off or not is a different matter. 

[winterof79]

5 minutes ago, snowice said:

No Easterly that's misleading later stages of ECM is same as yesterday 12z whether it comes off or not is a different matter. 

That is FI and not at 144-150Z as I was showing.Not convinced about an Easterly at any stage on ECM

Edited January 7, 2017 by winterof79

[IDO]

5 minutes ago, snowice said:

No Easterly that's misleading later stages of ECM is same as yesterday 12z whether it comes off or not is a different matter. 

I assume you are referring to the ECM 12z D10 chart compared to the 0z today? There is a huge difference UK wise:

Yesterday This morning

And of course it remains beyond D10 for any easterly on today's run, so with respect to ECM, pretty much no use based on recent performances at that range as it is still likely to over amp'ing the heights. If all the D10 ECM charts had verified we would be moving into our second month of a mini ice age!

[Frosty.]

A good start to the day from the 00z runs from a cold potential perspective, better than 24 hours ago..I particularly like how the Gfs 00z keeps reloading the cold zonal flow!

[Severe Siberian icy blast]

The only thing to note, more of an observation over the last 4/5 days really is the fact that the 0z consistently seems to be the flattest run of the day and the fact that the sceuro high is still there on the 0z could potentially give us at least something to keep an eye on this evening.

[knocker]

The 8-13 EPS anomaly indicates a Canadian/Greenland vortex with lobes to the west  A trough in the NW Atlantic and another in eastern Europe down to the Med and weak positive anomalies and some ridging over the UK. Ergo upper winds in the westerly quadrant with temps a little below average. The surface high would likely be to the SW.

Edited January 7, 2017 by knocker

[IDO]

14 minutes ago, Severe Siberian icy blast said:

The only thing to note, more of an observation over the last 4/5 days really is the fact that the 0z consistently seems to be the flattest run of the day and the fact that the sceuro high is still there on the 0z could potentially give us at least something to keep an eye on this evening.

The problem with that theory is that the mean doesn't support it:

d10 meand10 op

 

 

[radiohead]

You can see what the problem is. Too much "spoiler" energy squeezes out over the top of the high near the southern tip of Greenland. A familiar breaker of hearts to anybody who has been following the models for years. This is what happened on the 12Z but then didn't happen on the 18Z and now has happened again on the 0Z runs.

 

Edited January 7, 2017 by radiohead

[bluearmy]

16 minutes ago, knocker said:

The 8-13 EPS anomaly indicates a Canadian/Greenland vortex with lobes to the west  A trough in the NW Atlantic and another in eastern Europe down to the Med and weak positive anomalies and some ridging over the UK. Ergo upper winds in the westerly quadrant with temps a little below average. The surface high would likely be to the SW.

the propensity to increase the amplification of the upper ridge headed ne (just to our west) as we entered eps high res over the past 36/48 hours is notable. Whilst it currently looks odds on to collapse across us as per the end of the current suite, there comes a point at which the ridge gains enough latitude to force the pattern to change and the Euro trough backs west underneath to support it. as per the 12z op yesterday. The spreads seem to be firmly with the strengthening Atlantic running across to our north by day 10 but the next two runs will dictate if this trend of amplification continues to gain traction far enough nw to allow an easterly. 

in general, the extended eps are far more anticyclonic across nw Europe than the GEFS/geps 

 

Edited January 7, 2017 by bluearmy

[Summer Sun]

 

Edited January 7, 2017 by Summer Sun

[mountain shadow]

28 minutes ago, IDO said:

I assume you are referring to the ECM 12z D10 chart compared to the 0z today? There is a huge difference UK wise:

Yesterday This morning

And of course it remains beyond D10 for any easterly on today's run, so with respect to ECM, pretty much no use based on recent performances at that range as it is still likely to over amp'ing the heights. If all the D10 ECM charts had verified we would be moving into our second month of a mini ice age!

Just to be clear , it would be more correct to refer to ECM ops runs, not the whole suite.

If some people want to take day 10 charts as gospel then thats their downfall.

The teleconnections have never supported an Easterly.