Model Output Discussion - cold spell to end Autumn

[Paul_1978]

2 hours ago, Surrey said:

Thats not a Bartlett high setting up shop towards the end of the GFS run is it? I know it's way way FI but would be sods law that it materialises just to rub salt in the wound

It's so far away it's hardly worth mentioning. 

[Frosty.]

The Gfs 6z goes for high pressure from next weekend with overnight frosts and fog with crisp bright wintry days..could be worse!

[bluearmy]

extended clusters reveal 10% keeping cold winter going with amplified patten and upper ridging to our ne

around 60% are zonal with heights rising to our south and the other 30% cluster cool zonal with heights over Europe not rising 

[Had Worse]

Having read Tamara's post a day back, I would take the output with a pich of salt.

It will have the models flip floping again and may take some time to settle.

We will according to the METO, get some milder periods but the prognoses of a scandi ridge should keep it cold.

[feb1991blizzard]

I'm already sacking this and the medium term of as a bad job, I'm looking a long way up now to get some spiritual uplift, no I'm not going to suddenly start going to church, I'm talking about this.

[Had Worse]

Just now, feb1991blizzard said:

I'm already sacking this and the medium term of as a bad job, I'm looking a long way up now to get some spiritual uplift, no I'm not going to suddenly start going to church, I'm talking about this.

I can see a bright stratospheric warming to the North. ( modified nativity wording)

[Frosty.]

A seasonal 6z, lots of high pressure after the week ahead with cold bright days and frosty nights with probably some freezing fog. Then a white Christmas for Scotland...a lot more seasonal than the 00z turned out!

Edited December 9, 2017 by Frosty.

[feb1991blizzard]

4 minutes ago, Had Worse said:

I can see a bright stratospheric warming to the North. ( modified nativity wording)

And Just before dawn at the purpling of the sky, a snowflake from heaven just fell to the ground and the chaos began once again.

[Methuselah]

Given that I've never come across either a man or a machine that can accurately forecast our weather at T+384, I'll take the GFS 06Z with a ton of salt...Apart from some sort of Scandi/Russian block, not a lot else seems to appear with any great degree of consistency. So, for the time being, I'll take a glass-half-full attitude...and see how it all pans out.

[bobbydog]

Just now, feb1991blizzard said:

I'm already sacking this and the medium term of as a bad job, I'm looking a long way up now to get some spiritual uplift, no I'm not going to suddenly start going to church, I'm talking about this.

so am i feb. whatever is going on down here, the strat is taking a battering. that has to have big implications for the trop further down the line. if the stratospheric vortex is wound up tight, its difficult to see a way forward. by this point, it usually is. this year it is anything but...

going to be some fun times ahead this winter i feel....

[bobbydog]

Just now, Ed Stone said:

Given that I've never come across either a man or a machine that can accurately forecast our weather at T+384, I'll take the GFS 06Z with a ton of salt...Apart from some sort of Scandi/Russian block, not a lot else seems to appear with any great degree of consistency. So, for the time being, I'll take a glass-half-full attitude...and see how it all pans out.

fortunately pete, the strat forecast is much less prone to flip-flops (or any other form of footwear) so its all looking good for now 

[swfc]

3 minutes ago, feb1991blizzard said:

And Just before dawn at the purpling of the sky, a snowflake from heaven just fell to the ground and the chaos began once again.

I think a break from all this maybe needed feb,either that or a few beersAnyway 6z does try to bring in a semi scan high.fails but the"trend" is there along with the strat warming

[sunnijim]

Year after year this Winter model watching 'gets me'  every time.During the Autumn I convince myself that this year I won't be 'sucked In'

However this last 48hrs I find myself 'buying into' some sort of Northern Blocking as we head toward Christmas when it appars at 380hrs + on the GFS

When the model shows The p.v firing up in FI my reaction is to get cross and say In my mind, FI nonsense.

[Rocheydub]

43 minutes ago, Paul_1978 said:

It's so far away it's hardly worth mentioning. 

Is this not the model discussion thread? No?

Yes it’s FI, but it’s one of a number of options as we head forward to the festive week. Just because it shows what you don’t want, doesn’t mean you should tell someone it’s not worth mentioning!

[The Enforcer]

3 hours ago, bluearmy said:

Yes nick, from a personal perspective this has gone very well re the trough extension (ecm the call on this) but the warm front which came into play on Thursdays fax charts and disappeared yesterday morning is back today and it messes with the southern extent of the snowline. Euro 4 has now recognised this little low into the se of England preventing the push north of less cold uppers and mixing out of the cold with the snowline shifted south some 30 miles. however, looking at its 850/1000 thicknesses indicates that the warm front shown on the faxes is there. seems to be more emphasis on sleet/snow returning south later on tomorrow but looks messy and unsubstantial. The midlands however look like they will take a big hit tomorrow and this now extends into the n half of east anglia. (Away from the coastal strip which could be 20 miles or so)

Warm front has gone again on the latest T+24 Fax:

Would this not bring the southern extent of the snowline southwards ahead of the remaining occluded front?

 

 

[phil nw.]

The 00z ens graphs show some trend to less cold after the next 48hrs

which is not a complete surprise as the gefs/eps charts show a flattening of the Atlantic ridging in week 2 and upstream the demise of the Alaskan ridge from around day 7.

We may well squeeze another cold nw shot at the end of next week as current models are showing before that change over the west coast of NA translates to a flatter Atlantic jet by day 10.This is because the energy from the Canadian vortex is set free to move east as we lose those heights around Greenland..

so something more typical at least for a while in week 2 with a more westerly type but no suggestion of anything overly mild.

Just a glance further on looking at the ext Eps and no strong signal of any influence from the Russian heights further east but upstream indications of the Pacific ridge re-amplifying which may translate to the Atlantic later but that is going into week 3 so i will leave it there. 

Edited December 9, 2017 by phil nw.

[The Enforcer]

23 minutes ago, bobbydog said:

so am i feb. whatever is going on down here, the strat is taking a battering. that has to have big implications for the trop further down the line. if the stratospheric vortex is wound up tight, its difficult to see a way forward. by this point, it usually is. this year it is anything but...

going to be some fun times ahead this winter i feel....

Or in other words, the strat would be taking a battering if we got to Xmas day and the stratospheric pattern was still as shown on that chart.

[karlos1983]

Ens say our t2m will be like the Big Dipper at Blackpool until around the 17th, at which point the key word is probably “uncertainty” but overall a warm up seems the form horse..... for now. 

 

[bluearmy]

18 minutes ago, The Enforcer said:

Warm front has gone again on the latest T+24 Fax:

Would this not bring the southern extent of the snowline southwards ahead of the remaining occluded front?

 

 

That looks like an 'old fashioned snowmaker' chart - I guess you will see how much difference it makes if the warnings are changed markedly. Last I heard they were expecting the line to be Gloucester across to Luton and then across to s norfolk

latest euro4 looks pretty much identical to 00z run though snowline perhaps 10 miles north of 00z run 

[The Enforcer]

2 minutes ago, bluearmy said:

That looks like an 'old fashioned snowmaker' chart - I guess you will see how much difference it makes if the warnings are changed markedly. Last I heard they were expecting the line to be Gloucester across to Luton and then across to s norfolk

latest euro4 looks pretty much identical to 00z run though snowline perhaps 10 miles north of 00z run 

Several reports in SW Regional thread of various apps changing Sunday's forecast from rain to snow in the last few minutes: Gloucestershire, Wiltshire and even on the Dorset coast.

[ACCOUNT DELETED]

Can anyone tell me has the track of the low changed? Latest Arome run: gone is the milder air across South Wales tomorrow (initially for example Swansea was showing 10C and heavy rain) but if this is right, it would be 0-2C with snow or sleet! Look at the blues across Somerset & parts of north Devon too, again these areas looked milder on yesterday's runs as well! 

Edited December 9, 2017 by Draig Goch

[Frosty.]

Looking at the GEFS 6z mean, it's a half way house scenario compared to the operational with high pressure eventually becoming more influential across the southern half of the uk but staying more zonal further north..so, in a nutshell, according to this, the week ahead looks unsettled with cold then less cold then colder again followed by a gradual transition to more settled, especially  further south with plenty of surface cold bringing frosty nights and bright mainly dry crisp days but staying more changeable across northern uk with temps closer to average.

Edited December 9, 2017 by Frosty.

[The Enforcer]

I certainly can't see how this chart:

Could lead to this snow/rain pattern at that time:

[feb1991blizzard]

4 minutes ago, The Enforcer said:

I certainly can't see how this chart:

Could lead to this snow/rain pattern at that time:

The bottom chart is out of date now, it gets nowhere near my location until around 9am (and maybe not even at all in any relevant intensity), where as that chart has it dumping me at 6am until after midday.

[Derecho]

Hello

So after Monday's uncertainty we seem to have a pretty good idea as to how things will develop this week. A less cold interlude from Tues-Thurs, then a cold Friday and Saturday. Where things go from here are uncertain. Here is the key point at T132:



So the Azores high tries to move to Greenland but we have the deep low over NE Canada.... If this low moves east then the ridging of the Azores high is interrupted and the pattern is flattened. Seems to be appearing on most runs now. The Greenland high although cold based can extend the window of opportunity but it seems it won't hold on long enough (could change though). I think there are 3 plausible scenarios overall:

                   Scenario 1: 10%                                      Scenario 2: 40%                               Scenario 3: 40% - Though perhaps some cooler westerlies
 

The first a Scandi high offers a decent route back back into cold though its got to happen pretty quickly after Fridays northerly hence the lower probability.

The next two unfortunately see the PV strengthening around the S Greenland area. Scenario 2 however offers a chance to extend our cold by moving the anticyclone over the UK. That wouldn't be so bad because it would be cold and maybe the high could build and hold back the Atlantic. It could also sink but lets wait and see, that would be ~10 or more days away.  The final scenario is a return to what we have seen in recent years.  Some mild days with SW winds interspersed with colder westerlies due to the cold air outbreaks from Canada moving into the NW Atlantic.

These are just my interpretations of the model output though. Hopefully we will get a nice surprise but it wouldn't surprise me if the Atlantic woke back up again.