Model output discussion - proper cold spell inbound?

[Dacyfo]

5 hours ago, Yarmy said:

Insolation? 

The red line is roughly suitable for the UK. Of course the actual Watts hitting the surface will depend on cloud cover.

Edit: Image is from here:

http://www.physicalgeography.net/fundamentals/6i.html

 

Hi Yarmy,we're currently going into solar minimum.Does that also have any effect on the figures given on the diagram above? 

[Johnp]

This GFS run is a lot colder than you might think from looking at the synoptics.

Having a look at the 850s and theta e charts reveals the story.  Probably plenty of snow for the North West and hard frosts elsewhere.

That's getting the ground cold in prep for  the snowmageddon cold spell later in the month.

[Mark Neal.]

UKMO Cold uppers return for 144hrs.

 

[karyo]

1 minute ago, Mark N said:

UKMO Cold uppers return for 144hrs.

 

Wow, I wasn't expecting such deep cold uppers! 

[Ice Day]

Here are the 850's for the UKMO at 144, -8's for Ireland, Scotland and the North of England, -6's and -7's for everyone else. 

Very encouraging for those in the favoured spots, might even see Northwestsnow posting again???, 

Edited February 5, 2018 by Ice Day

[Ice Day]

Meanwhile back on the GFS, heights starting to build up towards Scandi at 216.  Very different from the 6z at the same time

12z  6z 

[ZK099]

Polar vortex in Greenland causing issues here. SSW might sort it out imminently though... 

[Summer Sun]

GFS and UKMO at t144 slight differences in the direction of the wind make all the different a tad more westerly from GFS and the air is a bit less cold especially in the south

[Seasonality]

7 minutes ago, Summer Sun said:

GFS and UKMO at t144 slight differences in the direction of the wind make all the different a tad more westerly from GFS and the air is a bit less cold especially in the south

Rather an understatement there Gavin!

[warrenb]

I think someone needs to tell the models there is an SSW under way. Suspect Meto still bullish about cold as the decider and Mogreps both take Strat into account.

[Man With Beard]

20 minutes ago, Mark N said:

UKMO Cold uppers return for 144hrs.

 

Best chance of widespread snowfall so far IMO. That ultra cold Canadian vortex is quite incredible. Just need a little disturbance in that flow (not too big mind!!). Do we actually need an SSW?

And just a little reflection ... must admit when I first saw -8C uppers forecast on an Atlantic flow I was a bit sceptical but here they are, made it all the way to T24:

  

[Summer Sun]

Just now, warrenb said:

I think someone needs to tell the models there is an SSW under way. Suspect Meto still bullish about cold as the decider and Mogreps both take Strat into account.

SSW is expected to happen around the 12th or 13th I doubt we'll see much from the models for a bit longer yet

[Frosty.]

Really like the nw  /  se  jet profile on the ukmo 12z @ T+144 hours which screams wintry reload after reload with snow showers, ice and frosts, even some frontal and back edge snow at times too!

[bluearmy]

2 minutes ago, warrenb said:

I think someone needs to tell the models there is an SSW under way. Suspect Meto still bullish about cold as the decider and Mogreps both take Strat into account.

Need to bear in mind that all the models go up to the upper reaches of the strat in the same single dynamic representation 

They all ‘take the strat into account’ as it’s part of the same model run!  They may, however, not be so good at modelling an SSW and it’s possible quick downwelling 

I suspect the ec op should be the best on this high up so the Berlin zonal windflow charts should give us a good idea of what’s happening 

[winterof79]

24 minutes ago, karyo said:

Wow, I wasn't expecting such deep cold uppers! 

Always worth noting the METO medium range updates in conjunction with model output. Rarely off the mark and looking cold.

[Froze were the Days]

30 minutes ago, karyo said:

Wow, I wasn't expecting such deep cold uppers! 

We've been here already this winter...Okay on elevated ground to the north, forget it if you live in the south (near normal temps beckons from that, 7c in East Anglia from the last Pm air mass that contributed to the snow in Southern Scotland, northern England back in January)

[ghoneym]

10 minutes ago, bluearmy said:

Need to bear in mind that all the models go up to the upper reaches of the strat in the same single dynamic representation 

They all ‘take the strat into account’ as it’s part of the same model run!  They may, however, not be so good at modelling an SSW and it’s possible quick downwelling 

I suspect the ec op should be the best on this high up so the Berlin zonal windflow charts should give us a good idea of what’s happening 

I think the Models will have ways of coping with 'polar convergence' - the physical distance for a given degree of longitude will vary from equator to pole - not only at the surface but aloft as well. Some centres will skew the grid they use to make sure that the primary area of interest is over them, so 'notional' poles will result which may affect, even if only slightly, the forecast over the domain further away. So I think that @warrenb will be correct in respect of MOGREPS vs what GFS would input as starting data.

[Catacol]

3 hours ago, chionomaniac said:

Not necessarily so, as the main daughter vortex is very much Atlantic based which still allows some type of Scandi block - but it may be a type of stand off situation with the UK temporarily held in no mans land until the vortex veakens

That's how I'm reading it... and I think MetO text suggests they are too. I am very suspicious of model output at the moment - there is a lot to be resolved over the next 7 days and I don't believe NWP has a handle on it. I have advertised one potential nirvana outcome... but have to acknowledge that, until we actually see the vortex split and the warming shred the circulation forcing a SSW reversal, we are partly guessing as to where the coldest air that is certain to spill out of the arctic will land.

Outside my front door I hope.

[ITSY]

This is interesting from the ECM, marked drop into substantially negative territory predicted for AO:  

NAO starting to trend downwards, albeit with the pace of Mertesacker's defending: 

Seeing as we only have access to one OP member at the timeframe concerned, I still think we could be several days at least off seeing the really juicy charts appearing in FI. If the NAO doesn't go negative and the eye candy hasn't started to appear by the end of this weekend, then I would start to wonder. Until such a time, enjoy this week with an eye on what could come - much of which is still largely out of op range! 

Edited February 5, 2018 by ITSY

[ICE COLD]

19 minutes ago, Froze were the Days said:

We've been here already this winter...Okay on elevated ground to the north, forget it if you live in the south (near normal temps beckons from that, 7c in East Anglia from the last Pm air mass that contributed to the snow in Southern Scotland, northern England back in January)

No that's not true mate . I live in Hertfordshire 10 miles from Cambridge and I have had 2 decent snow events this winter from NW winds .  The first event around the middle of December we got 4 inches . And the second one between Christmas and new year 2 and half inches . So it can deliver in the south . ?

Edited February 5, 2018 by ICE COLD

[bluearmy]

3 minutes ago, ghoneym said:

I think the Models will have ways of coping with 'polar convergence' - the physical distance for a given degree of longitude will vary from equator to pole - not only at the surface but aloft as well. Some centres will skew the grid they use to make sure that the primary area of interest is over them, so 'notional' poles will result which may affect, even if only slightly, the forecast over the domain further away. So I think that @warrenb will be correct in respect of MOGREPS vs what GFS would input as starting data.

Well, anything over gfs works anyway! FWIW, glosea was developed with the strat in mind and ecm op has excellent horizontal resolution in the upper strat

no idea re mogreps-15

[Froze were the Days]

15 minutes ago, ICE COLD said:

No that's not true mate . I live in Hertfordshire 10 miles from Cambridge and I have had 2 decent snow events this winter from NW winds .  The first event around the middle of December we got 4 inches . And the second one between Christmas and new year 2 and half inches . So it can deliver in the south . ?

From a straight polar maritime air mass from the north west?...that spell back in December (near mid-month) was largely from trough disruption in the colder air (mainly overnight and early morning) and falling in calm conditions.

[tight isobar]

Certainly again we have 'certain' model miss-managment to a degree!!

And as some have said ecm op- should begin to note of atmospheric switch-via mjo/ssw.

No hidden thing that it is the amp-mod but has decent outlet in picking these up even if @times

over dramatic with amplification synops.

Things about to change gear i reckon!!!!

Edit; even the shorter term in partial doubt...as the change in dynamics are being sniffed at via models.

Edited February 5, 2018 by tight isobar

[Catacol]

Musing about Feb 15. Amy Butler has tweeted an expectation that the SSW of Feb 12 will begin to force storm tracks equatorwards after about 3 days. This is the ECM for the start of that potential process

I'm seeing very cold air dropping into the mid Atlantic with pressure rising to the north and Scandy pressure also I suspect on the rise. Storm track set to shift further south as impacts of the reversal are felt and cold begins to tumble southwards.

Is this the precursor to the mother of all undercut scenarios?? I wonder what ECM would look like for weekend of 17/18. A bit of southerly adjustment and this would be the biggest blizzard since... well.... the last time we had a big blizzard.

Hmmmmmm.

Edited February 5, 2018 by Catacol

[offerman]

1 hour ago, weirpig said:

Yes that does look alot better  more of a North West South East axis on the UKMO    some showers of the wintry type of would have imagined 

In My opinion we need the High to revert to this position that ive marked for brilliant snow possibilities. I remember a Michael Fish forecast back in thje 80`s with he used the magnetic symbols and two highs joined in to one and extended right up as i marked.So it is possible.