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

[Seasonality]

Just out of interest. GFS and Met Office have definitely undercooked temps for the European cold spell. Something that @jvenge has noted too. ECM has been much better but even it was a little conservative for today. Something to watch for upcoming potential UK spell.

[Spah1]

24 minutes ago, Steve Murr said:

@Trom

here are the ECM spreads

144 - shows a small cluster in the atlantic relating to what UKMO shows - ( the low lifting out from under the high & moving E towards the UK )

NB : GFS op @ 168 is the fastest east of the 3 models showing a band of PPN crossing the UK- expect that to trend west in the following runs

ECM spreads 168

clearly some divergence around the amplitude of any wave coming off the states

ECM 192

The uncertainty spreads NE & magnifies with time relating to the possible high pressure... 

S

 

Just for us newbies why is that Low in the Atlantic on the UKMO not good news? 

Edited January 8, 2017 by Spah1

[Summer Sun]

16th onward the GFS Op is on the warm side of the mean 16th to 22nd ish the control is also on the warm side of the mean

The only full country warmer than the UK and Ireland is this morning is Cyprus even Malta is colder than the UK

Edited January 8, 2017 by Summer Sun

[Man With Beard]

39 minutes ago, IDO said:

Looking at the D10 mean from ECM, that is clearly moving away from support for the op, and another ECM backtrack expected this evening. In fact the GFS and ECM d10 broadly on the same page:

 

It's not a complete different picture to the op, but just flattened a little and cold air pushed into C Europe - which must remain the most likely outcome. I wouldn't expect the op to be a complete outlier, just at one end of the reasonable spread. And as was well explained last night on here, a few troughs over Scandi would completely skew the picture (worth checking the spreads - nothing major over Scandi suggests not many deep lows over there, so this idea unlikely).

Oh and regarding D10 verification, can't remember where from but a chart about a year ago was posted showing the ECM ensemble mean at D10 was king of verification stats, well ahead of the op. So completely agree with your idea for D9/D10 - perhaps a 50/50 weighting of the op and ens at that timescale would make a reasonable guide?

Edited January 8, 2017 by Man With Beard

[Ali1977]

ECM Op not an outrageous outlier by any means, all ENS look pretty cold at day 10 in De Bilt 

Edited January 8, 2017 by Ali1977

[bluearmy]

The GEFS /ECM mean anomoly agreement at day 10 is notable. (As IDO posted)

Given the op/control agreement on the ECM 00z run and the ensembles not going any further than they were with shifting the ridge to a high enough latitude to deliver a proper easterly, I would say we may as well not over analyse any possible easterly as its currently more likely to be a weak continental drift (still cold though).  However, I still think odds are on a mid lat block rather than any zonal mobile flow. 

This eps run could simply be a holding pattern ahead of a further amplification next suite but as IDO also pointed out, upstream is messy and I'm not sure downstream is particularly well modelled as yet. 

[Midlands Ice Age]

Can I spot a -51C in the polar airmass?

 

 

12 minutes ago, Summer Sun said:

 

That is really cold!!!!

[Osbourne One-Nil]

Just to remind people, this is the Model Discussion Thread, not the Ian Ferguson Twitter Thread!

With thanks

OON

[Purga]

Of course the only outcome has to be P16

 

[Luke Best]

2 minutes ago, Midlands Ice Age said:

Can I spot a -51C in the polar airmass?

 

 

That is really cold!!!!

That's the windchill, but minama temperatures not far behind in N Russia.

[Met4Cast]

18 minutes ago, Spah1 said:

Just for us newbies why is that Low in the Atlantic on the UKMO not good news? 

The low stops high pressure in the Atlantic from building North-Eastwards and we'd likely see a return to milder Westerlies similar to the GFS. 

The ECM doesn't develop that low so the high builds Norh-East and we end with an Easterly. 

[Ali1977]

The GFS nowhere near as good as the ECM but this still looks good, my area good be a hotspot away from the hills if this is correct.

[chris55]

16 hours ago, chris55 said:

That slider attempt on the GFS 12z caught my eye so i thought id compare the GFS and UKMO at 144 to see how they were both dealing with that time frame.

More often than not these sliders trend further southwest as the verification date comes forward so if something akin to the GFS 12z did come off then the possibility of a boundary snow event is possible.

We can see the differences between the GFS and UKMO at 144 clearly, the UKMO looks cleaner and potentially with colder 850s, but the GFS develops the energy "between" the highs (out in the Atlantic ) whereas UKMO keeps it to the West. Subsequently GFS develops that "potential slider" where UKMO offers the Iceland low alone which could well drop south east, but hard to be confident without a 168 chart.

I have got my Crayons out to show what I mean

GFS 144, developing the energy "between the highs"

Which leads to the Low pushing east and offering that potential "slider"

However UKMO ridges the Atlantic/Azores high keeping the two Lows separate, no slider but a colder feed, with the prospect of the Iceland Low pushing south east.

Not sure which option is better longer term TBH but does highlight that with this complex troughing in a cold flow nothing is nailed down and plenty of wintry prospects, even for those down south are available!!

 

How the models eventually deal with "that low" out west will have a marked effect on where we go after the initial northerly.

The 12z's from last night (as above) were handling it differently between themselves and it seems UKMO has trended towards GFS on the 00z.

ECM doesn't develop it and hence we get a cleaner evolution to the easterly.

However if it does develop and trend south west as is often the case with these types of lows then some places could see a lot of snow from it! But it may hinder the development of any easterly.

UKMO 120 144 low to the west pushing east over the ridge.

ECM 120 hasn't developed the low

Lots to be decided yet!

 

Edited January 8, 2017 by chris55

[SMU]

24 minutes ago, Ali1977 said:

ECM Op not an outrageous outlier by any means, all ENS look pretty cold at day 10 in De Bilt 

& the extended-

control looking good as well-

@Spah1 will do a post this morning on that- @chris55 has it nailed

ECM has the low going west under the high at 96

UKMO lifts it up & through slow

GFS lifts it up fast & east becoming the snow event & 168 which will be unlikely..

S

 

Edited January 8, 2017 by Steve Murr

[Ali1977]

5 minutes ago, Steve Murr said:

& the extended-

control looking good as well-

@Spah1 will do a post this morning on that-

S

 

This is interesting, they must be pretty similar and this would be a very very cold Easterly, especially with that crazy cold to our east.

lets see if the GFS prolongs the cold, I doubt it will show anything else. If an Easterly turns up this place will melt down.

Edited January 8, 2017 by Ali1977

[TEITS]

The fact the ECM control follows the Op has slightly improved the chances of an E,ly. Regardless of what the other ensembles say you always take note when the control follows the Op.

On a different note I realise everyone wants to see some snowfall. However at this range its pointless and you won't have a better idea until midweek. Even then it always comes down to nowcasting.

[bluearmy]

a few obseravtions

the drift away from any neg AO complete now on all the ens 

some appetite for a weakly neg NAO on the means and certainly the ec op and control

not that long ago that a decent neg AO/NAO combo was looking likely

as I mused this time yesterday morning, the NH profile later week two could well be supportive of some blocking further north than we have so far seen. The drift away from low heights over e Canada as a very positive upper temp anomoly establishes there will weaken the northern arm. There is some disagreement between eps and GEFS re how much residual vortex is left around n Greenland locale so, taking that into account, I would plump more scandi than Iceland for possible upper ridging. 

[The PIT]

Good agreement between the models until T120 then they start going there separate ways. Nice to see the cold shot actually get into the reliable time frame which hasn't happened a lot this winter. May get the first snow of the winter from this.

[chris55]

Am I right in thinking the ECM postage stamps to 168 are no longer available for free?? I swear they used to get posted. 

Would be very interesting to see how the individual members deal with the Atlantic low.

[SMU]

So people this is the low to look at on the 06z GFS & UKMO 12z to see if theres any swing to the ECM 

( also any ridging NE behind it off the states )

ECM day 5 - doesnt develop the low & it stays weak under the high

UKMO lifts it up & develops it slower

GFS lifts it as well but note how flat & fast the jet is coming off the states - so as a result when the low lifts out it gets fired east quickly across the UK

 

The UKMO is middle ground today & MAY still be as good as ECM at 192 with that atlantic low coming sharper SE instead of GFS east- but the pressure building behind it would have been inhibited so perhaps less amplitude....

S

[Severe Siberian icy blast]

12 minutes ago, Steve Murr said:

& the extended-

control looking good as well-

@Spah1 will do a post this morning on that-

S

 

Steve I don't think Iv ever saw a post from you where your battery power isn't in the red. . .  Use a charger!!!! Lol 

anyway yes the control looks good but Iv had to many false garden paths to look that far, just going by the spread up to t240 it's good news that the op has a fair bit of support, it's more than possible to have an easterly without high Lat blocking , as long as the trough to the south is strong enough to prop her up and squeeze the isobars then there's always the chance that further trough disruption can happen from the lows from the west, once we get energy squeezed under its much easier to make it sustained. The truth is knowone knows who will be right and it's an evolving situation but at least we are finally staring down a loaded gun for the second half of the week at the very least, I really hope we all see some snow and it will make interesting viewing as the days pass.

Edited January 8, 2017 by Severe Siberian icy blast

[northwestsnow]

6 minutes ago, TEITS said:

The fact the ECM control follows the Op has slightly improved the chances of an E,ly. Regardless of what the other ensembles say you always take note when the control follows the Op.

On a different note I realise everyone wants to see some snowfall. However at this range its pointless and you won't have a better idea until midweek. Even then it always comes down to nowcasting.

Yes snow distribution will become clearer by tomorrow/Tues Teits.

I suspect the flow will be that strong showers will be blown well inland.

We'll see.

Ps still think altitude is going to play a big part in all this..

Edited January 8, 2017 by northwestsnow

[Frosty.]

1 minute ago, northwestsnow said:

Yes snow distribution will become clearer by tomorrow/Tues Teits.

I suspect the flow will be that strong showers will be blown well inland.

We'll see.

I'm looking forward to the yellow be aware warnings followed by Amber!

There is going to be significant snow for some parts of the uk with drifting in the strong Arctic winds..bliss

I hope the Ecm is right and prolongs the cold through week 2!

[SMU]

GFS 06z this is where to look

Azores low less developed further west & slower = better 168 profile

 

 

 

Edited January 8, 2017 by Steve Murr

[Singularity]

7 minutes ago, Steve Murr said:

So people this is the low to look at on the 06z GFS & UKMO 12z to see if theres any swing to the ECM 

( also any ridging NE behind it off the states )

ECM day 5 - doesnt develop the low & it stays weak under the high

UKMO lifts it up & develops it slower

GFS lifts it as well but note how flat & fast the jet is coming off the states - so as a result when the low lifts out it gets fired east quickly across the UK

 

The UKMO is middle ground today & MAY still be as good as ECM at 192 with that atlantic low coming sharper SE instead of GFS east- but the pressure building behind it would have been inhibited so perhaps less amplitude....

S

Good to see this less presumptuous take on the UKMO run; there is indeed a possibility that there is a sharp enough ridge following on for it to build across north of the low as it tracks trough the UK. This being because the upstream pattern is not nearly as flat as GFS has it.

In keeping the mid-Atlantic low trapped under the ridge, ECM effectively negates this conundrum but it still needs the less progressive N. American pattern to get so much of an easterly in place later... though given the warming trend in the NE of N America, a slackening jet could even in theory allow for an initially mid lat block to gain latitude with time - but only if we don't see the tropics misbehaving. The possibilities are not endless, but they don't stop far short