Model output discussion - winter proper underway

[northwestsnow]

Ec looks colder than average christmas day !!!

[swfc]

Ecm shows a lack of push from the pacific from this morning and the run has a totally diff look.seems any consistent run atm is not on the cards imo

[northwestsnow]

Not keen on 240 but i'm preety sure EC gives a white christmas for NW Britain in particular (probs altitude dependent).

[blizzard81]

The ecm ops definitely have an issue with their transition from day 8 to day 9.  I mentioned this last night when it went from 1035 high over Nova Scotia at day 8 to 985 low at day 9. Suffice to say this hasn't happened on tonight's run between days 7 and 8 - nothing like, which isn't surprising as it was totally outlandish. However, it has come up with another outlandish transition tonight between days 8 and 9. The pv over our side of the hemisphere near on trebles in size in the space of 24 hours! I think I will join the ecm and get drunk! 

Edited December 16, 2017 by blizzard81

[knocker]

The ecm det. rather continues the inference from this mornings EPS anomaly of not making so much of the Azones ridging north in the vicinity of the UK as the others. Ergo more unsettled. Will be interesting to see this evenings

 

 

Edited December 16, 2017 by knocker

[Guest]

SHORT GEFS 12z ENSEMBLE SUITE ANALYSIS

Further to my long "northerlies vs easterlies" post on page 59 where I included some of the impressive charts from the 0z and 6z output, I now turn briefly to the GEFS 12z output. Firstly, yet again, I see some comments stating a poor run and this must be that minority who only look at the "Europe" view charts (this is so misleading - how many more times do I have remind these few posters about this?). The "Northern Hemisphere" view charts have far greater interest for coldies and the last 4 runs have actually been pretty consistent.The only difference that I have spotted in the 12z output is that perhaps that it is marginally less progressive but it is still singing from the same hymn sheet. Now, I just haven't got time this evening to post all the charts and analyse each of them individually but here is the panel for the end of the run (too small, I know - if anyone can show me how to get a large image of the panels, I'd really appreciate a PM or sticky note about it): 

                                                                                                                           

In summary, I have noted the following from the 20 ensemble members:

1. 18 of them have either positive or very positive PNAs and only 2 are neutral or slightly negative. Remember this is one of the first indications of what we are looking for in terms of setting up a broad pattern change to the cold regime.

2. 15 of them have the PV either starting to split, half split or fully split. Only a handful have a quite strong looking PV and even most of these are under attack. 

3. 19 of them have HP close to the North Pole - some of these have intense HP and plenty of ridging in various directions. Only one has very little HP.

4. Over half of them have HP close to or over the UK. About half of these still show us under quite mild westerlies. A few of them have us under LP or in quite a cyclonic pattern - several are with Polar Maritime or Arctic air in the mix. 

5. 7 of them have Scandinavian HPs of various types, several are well developed and 3 show easterlies already established. 

6.Only a few have deep LPs (see below).

Here are a few of the highlights from the T+384 ensemble suite:

                 PERTURBATION 8                                                        PERTURBATION 13                                               PERTURBATION 14 

                                                             

Pert. 8 has HP ridging from Scandi to Greenland and getting close to a brilliant cold set up - not far from an easterly as the LP is pushing south. Pert.13 also has the Scandi HP but ridging across to a proper "cut-off" Greenland HP with the UK already under an easterly. Pert. 14 has another GFS "super LP" south of Greenland with sub 915 mb central pressure equaling or beating the North Atlantic record of 914 mb (882 mb for hurricanes). Even this chart shows the PV under attack. 

 

                  PERTURBATION 15                                                   PERTURBATION 17                                                PERTURBATION 20 

                                                            

Pert. 15 is one of the very few with a pretty strong PV but the far side of the Arctic has much higher pressure and a + PNA. So, even the worst looking chart is still not too bad. Pert. 17 has a fully split PV with HP north to south through Pole and the Arctic with a strong Scandi HP and an easterly developing over us. Pert. 20 has an intense Russian HP ridging into the Arctic and shattering the PV. The LP to our west is developing a negative tilt and we're under a south-easterly which is veering into the east as the LP will undercut it all.

Edited December 16, 2017 by Guest
Correct typos and check charts

[Decemberof2010]

Excellent post BB62-63. Thank you for your in depth and knowledgable posts. It helps us mere lurkers to understand a bit more. Keep up the great work. 

[northwestsnow]

GEM is awful from a cold perspective- no denying that.

EC probably has showers turning wintry late christmas eve in NW Britain before sweeping through the rest of the UK on Christmas Day-

Boxing day however sees TM air take over from PM air.

Still, a white christmas for some!!

EC snow depth chart confirms- much of NW Britain has lying snow by christmas day

Purely for fun at that range but shows there is still the chance.

Edited December 16, 2017 by northwestsnow

[bluearmy]

Credit where credit is due judging by the evolving ecm ens runs - the feedback in the se states due to the rockies as discussed a few days ago re joe B - he looks to be right 

Edited December 16, 2017 by bluearmy

[northwestsnow]

4 minutes ago, bluearmy said:

Credit where credit is due judging by the evolving ecm ens runs - the feedback in the se states due to the rockies as discussed a few days ago re joe B - he looks to be right 

I missed that blue- can you divulge..

[Summer Sun]

UKMO extended starting to look a bit more windy in the north with some longer spells of rain in the north and west

[bobbydog]

Just now, Summer Sun said:

UKMO extended starting to look a bit more windy in the north with some longer spells of rain in the north and west

which is nice...

[I remember Atlantic 252]

4 minutes ago, Summer Sun said:

UKMO extended starting to look a bit more windy in the north with some longer spells of rain in the north and west

Dry in the south though! not bad

[Mokidugway]

2 minutes ago, Summer Sun said:

UKMO extended starting to look a bit more windy in the north with some longer spells of rain in the north and west

Like a serpent of misery ready to spread its poison across the uk , storm Dylan,lol

[feb1991blizzard]

Ext EPS aren't tragic but the pattern looks a bit too far East to me.

[SLEETY]

You can see why the METO mostly ignore Gfs output,especially when it hits low res,its complete junk.

Look at all these low pressure systems it shows hitting the Uk like that 

Actually it’s been said before it’s pointless that it runs to so many days ahead,but it still happenseven now

 

[Dennis]

first christmas day - high pressure South of ICELAND to SW Ireland/UK - Azores

Edited December 16, 2017 by Dennis

[knocker]

1 hour ago, northwestsnow said:

Not keen on 240 but i'm preety sure EC gives a white christmas for NW Britain in particular (probs altitude dependent).

Might be a tad breezy

[Dennis]

so where will the ridge be around christmas?

[swfc]

1 minute ago, Dennis said:

so where will the ridge be around christmas?

Hi

Where and what is this showing???

[Dennis]

Just now, swfc said:

Hi

Where and what is this showing???

hi its showing what i said: an ridge is maybe setup near NE of the USA - that is usefull for cold air in NW Europe

[Had Worse]

12 minutes ago, knocker said:

Might be a tad breezy

Yes.

85.5 Knots max on that chart equates to 98mph.  Is that sustained with higher gusts?

 

EDIT: Answering my own question, its at roughly 5200 ft above sea level that its blowing that hard.

Edited December 16, 2017 by Had Worse

[stodge]

Evening all

Plenty of interesting model watching currently and it could well be midweek before the far south and SE see a significant warming in temperatures so while it's no 2010, December 2017 may well turn out colder than many of the more recent examples.

A lot of agreement on the 12Z output tonight - HP builds in strongly from the SW from tomorrow bringing much milder SW'ly winds to northern parts of the British isles but with quite an intense HP (up to 1045MB) sitting just to the south, the far south has lighter winds and a greater risk of frost and fog and with the nights almost as long as they can be there's a chance that fog could linger in favoured spots.

The HP begins to withdraw steadily later in the week as stormy and vigorous LP start to move south and SE - here's ECM for Boxing Day:

GFS 12Z OP angles the LP differently:

The Control takes it even further:

The idea of NE heights remains at the far edge of FI (basically around New Year) but for Christmas Day the cold ship has sailed in my view. 

ECM and GFS OP FI bring the jet south and allow much stormier and more unsettled conditions to sweep in from the Atlantic and that looks perhaps the "form horse" for the immediate post-Christmas period and if you are a coldie, remember always the route to very cold begins from very mild so a blowtorch Christmas Day with the HP building through Europe to the east may pay dividends at New year but the Atlantic looks to be in a strong phase at present and my view remains we are now entering a 10-14 day (minimum) period of Atlantic domination but that will still leave a lot of winter.

[Dennis]

33 minutes ago, Dennis said:

hi its showing what i said: an ridge is maybe setup near NE of the USA - that is usefull for cold air in NW Europe

 

[Dennis]

42 minutes ago, Dennis said: