Model output discussion - 1st December onwards

[Mucka]

10 minutes ago, phil nw. said:

The word transitional mentioned in that MO outlook suggests mobile perhaps with more emphasis on pm air incursions getting further south.I am only speculating of course it could mean a mid-latitude uk high with surface cold -who knows?

 

 

Could be, the wording is a little ambiguous and hard to know if the last sentence is referring back to period after mid month rather than later in the month where they mention cold.

My guess would be some form of blocking later for them to mention cold (and drier) rather than PM incursions on a mobile set up which I think they are favouring in the period just after mid month.

 

Hopefully Fergie will pop in later and explain all.

 

Edit 

Reading bryan 629's post it sounds like he is describing some sort of ridge/trough scenario which of course could give cold snaps and millder interludes but also lead to blocking proper.

Edited December 3, 2015 by Mucka

[Paul]

8 minutes ago, bryan629 said:

This is what Fergie tweeted yesterday 

an Fergusson ‏@fergieweather  Dec 2

W COUNTRY CONT'D (5/5) Signals are more mixed later Dec. Hints of a waning of more vigorous weather; more changeable & *perhaps* colder too

Ah good timing -  a nice feature the new software is that if you get the link to a tweet you want to quote, it'll embed if you just paste that in:

 

[Duane S.]

Certainly not convinced HLB is 2 weeks away but sure am picking up a trend that lower heights will be slipping into mid Europe by then.

Edited December 3, 2015 by s4lancia

[mb018538]

Let's be honest here, the models have been teasing a cold blast in FI for the last 2 weeks! As the time has drawn closer, it's not got any closer!

[Bristawl Si]

11 minutes ago, mb018538 said:

Let's be honest here, the models have been teasing a cold blast in FI for the last 2 weeks! As the time has drawn closer, it's not got any closer!

Yes...normal weather model outputs in Winter isnt it? I'll get my coat.....

[knocker]

Good job this wont verify but always a danger in this sort of set up that one of these destructive storms will track a tad further south. Gusts in excess of 80kts we can do without.

Edited December 3, 2015 by knocker

[Captain Shortwave]

 

ECM please try again....... 

Heights look to remain high over Europe for the next 10 days, receding somewhat later but the ensemble signal later on looks rather mixed in terms of a clear signal. The GEFs in particular not offering much consistency.

The 12z suite deepens the Atlantic trough, but again each suite seems to offer something a little different.

Overall again some hints of losing the zonal signal to a degree but how the longwave pattern sets up is still up in the air at the moment. Lets hope for a bit of luck for something either anticyclonic or cold with a trough to our east. 

 

 

[nick sussex]

The ECM at T216 hrs has the main PV  located towards Siberia with a chunk left in Greenland, broad troughing over much of the USA and high pressure pushed east into the Atlantic.

It looks very messy and unconvincing between days 8 to 10 but there are some changes upstream with more amplitude. The Euro high has returned and is set to be about as welcome to the European ski resorts as a bikini salesman in downtown Jeddah .

 

[mountain shadow]

5 minutes ago, nick sussex said:

The ECM at T216 hrs has the main PV  located towards Siberia with a chunk left in Greenland, broad troughing over much of the USA and high pressure pushed east into the Atlantic.

 

If memory serves me correct from large Winter this was a common occurrence, when the main PV shifted away from Greenland it always left a small daughter vortice behind keeping the tonality going.

[bluearmy]

7 minutes ago, nick sussex said:

The ECM at T216 hrs has the main PV  located towards Siberia with a chunk left in Greenland, broad troughing over much of the USA and high pressure pushed east into the Atlantic.

Many of the fi ens runs were shifting the vortex to the Asian side and leaving nothing around Greenland. The reality as time ticks down is that a chunk at the very least will remain in the Greenland sector.  Without that, we would indeed be seeing some of those very amplified Atlantic solutions coming to fruition in the 8-10 day timeframe modelling. 

[Evening thunder]

1 hour ago, bryan629 said:

This is what Fergie tweeted yesterday 

an Fergusson ‏@fergieweather  Dec 2

W COUNTRY CONT'D (5/5) Signals are more mixed later Dec. Hints of a waning of more vigorous weather; more changeable & *perhaps* colder too

We've had 'vigorous weather' down here?

Must have been just too far north to affect the SW but still affected the area known as the west country then.

[nick sussex]

3 minutes ago, mountain shadow said:

If memory serves me correct from large Winter this was a common occurrence, when the main PV shifted away from Greenland it always left a small daughter vortice behind keeping the tonality going.

Yes this was often the case, the models seem to be too eager to completely remove a chunk of the PV and that's why I'm always dubious of this at longer timeframes. I think looking at the ECM I still wouldn't rule out something colder because there are some upstream changes, but nothing substantial because of that PV chunk to the north.

[Iceberg]

The models have been playing with and dropping buckling and transient highs in the T216 to T300+ time range.

However what we have this time round is different. Even at T120 the ECM screams promise with the building of the high over the pole. Later in the run the high builds further and moves towards Greenland, thanks to the relocation of the PV. All of this is perfectly feasible and natural imho.

by T240 the stalled low pumping up WAA up the east coast of the N.America would only really led to the continual migration of the artic high over greenland.

I appreciate this goes against strato indications, however the lower forcing and upstream signals are very conclusive.

Not a certainty, but not be discounted as we enter mid month and the second half of Dec.

[Singularity]

 

 

That's the critical point in the GFS 12z det. run wrt to the polar setup IMO, as the Arctic High manages to squeeze in between areas of lower heights and act as a catalyst for rising pressure over Greenland. It's made possible by the ragged state of the vortex, but this also means the positioning of features is highly uncertain. The run hints at a west-based -ve NAO but then progresses the pattern east once into lower-res (beyond +240), allowing the northerly flow to encompass the UK. That the high manages to sneak NE and become a feature over Scandi with trough disruption west of it is again testament to the ragged polar vortex at the tropospheric level. It's pretty remarkable given the potency of the stratospheric vortex during the period, and I suspect it owes a lot to some dramatic changes in atmospheric angular momentum that the model keeps predicting beyond about week's range. It would be surprising if they weren't toned down, with less immediate vortex disruption as a result, but there does seem to be plenty of scope for a cold snap of some description in the middle of the month.

ECM actually follows very similar lines tonight with its 12z det. run, but also has LP riding up across the eastern U.S. which is typical of an El Nino atmospheric state and could serve to prevent a mid-Atlantic ridge from linking with the HP over Greenland.

From a polar perspective, the run is far better than the 00z det. was in terms of keeping the polar vortex disorganised and holding the door open wide for amplifying waves to keep pressuring the strat. vortex while we wait for it to become more vulnerable later in the winter.

Posted at 19:42 on 3rd December. 

[Man With Beard]

Nothing to add to the detailed analysis, so forgive me going with a broad brush one - my gut feeling looking at the charts is that the next two-three weeks will be broadly the same - but given the profile of the NH, there's a high chance of some colder days at some point as a front pulls down from the NW. As long as a decent chunk of low heights remain in to our NE, they are just begging an Atlantic low to attach itself and swing through to the south of it - which will lead to a NWly following on behind. The vortex over Greenland doesn't look so deadly as to forbid a brief interlude in the low pressure train, too.

And anything from the NW so far this winter seems to have a little more bite than usual - so not out of the question that a 24 hour snowy period may arise. Basically we just need a little luck - but I don't think we need that much.

Apart from that - mild, windy and occasionally wet.

[Summer Sun]

Quite a lot of mild air for mainland Europe which at this time of year isn't good for the ski regions

Edited December 3, 2015 by Summer Sun

[knocker]

Tonight's anomalies at T240 still looking at the same upstream pattern thus no appreciable change downstream with periods of unsettled weather continuing over the UK with some wintry outbreaks of wind and rain with snow thrown into the mix up north. Temps quite variable depending on the weather system in play at any particular time. Looking further afield into the ext period there is no significant change with the GEFs or the ecm so really much of the same and NOAA doesn't suggest anything to abuse that idea.

http://www.tropicaltidbits.com/

 

[cold snap]

There is no support for Ecm tonight 

Not saying its going to turn bitter but there run is not supported 

http://projects.knmi.nl/exp/pluim/Data/pluim_06260_0_12_60.png

[winterof79]

Nothing other than early traditional winter fayre to my eyes.As I said to my daughter earlier the fun and games in most traditional winters start around New Year.

Which is fine by me as I am away until New Years Eve.

A respite from wind and rain would be good after this weekend.The central swathe of the UK looks to be in trouble

EDIT I see Cold Snap has beaten me to the ECM Pluim

 

Edited December 3, 2015 by winterof79

[Mucka]

Looking at London ensembles they are not without hope for cold lovers

 

 

Still a few cold runs and much fewer mild runs

[Blake]

Hi all, been browsing past few weeks, but finally starting to see trends changing to something a bit more seasonal. Nice run in FI in P12 on the ensembles. HP building over Scandi with jet to the south, would expect the low off south of Greenland to slide south of the UK between HP to NE and SW towards the Mediterranean. Cold beginning to flow from the East, -8's not far away, thickness could be improved. Let battle commence!

[Mucka]

GFS different again so very difficult to know what we will end up with but the general theme is to slowly get rid of the Euro high and attempt to push a trough into Europe which if correct would at least give us a chance of some cold and snow.

 

Also nice to see the odd cold run appearing in GFS ensembles albeit in FI.

We could be viewing much more promising charts by next week if we are very lucky

Edited December 4, 2015 by Mucka

[northwestsnow]

GFS brings in a pretty potent northerly in FI (again). With the jet sinking south and in its wake a potent arctic blast 

I will make my christmas wish now please santa !

 

[Mucka]

1 minute ago, northwestsnow said:

GFS brings in a pretty potent northerly in FI (again). With the jet sinking south and in its wake a potent arctic blast 

I will make my christmas wish now please santa !

 

Ho ho ho

 

[The PIT]

Pretty much as you were model wise windy at times mostly on the mild side. The normal FI teases  looking a bit like last DEcember where we didn't see any snow until boxing day when we got loads