Hunt For Cold: Model Discussion - Heading Into Christmas

[SteveB]

59 minutes ago, Glacier Point said:

Just a reminder. Stratospheric time scales are extremely slow. Modelled effects of the warming not likely to show until 7th January at the earliest. That's still a few days yet before it gets into GFS range. 

This spikes my interest, purely because if you look at historical CET's, there are only one or two very cold January's (Sub 2c) that follow a + 6 CET December, which we are likely to see, if not high 5's

But a mild first half of Jan can off set a very cold second half giving a CET of 3c for which there are plenty 3c January's following mild Decembers.

 

[karlos1983]

1 minute ago, weirpig said:

Think its to far out to make that assumption with much confidence    anyway i believe the ECM 0z ensembles mean  has a split  and moves it favourable  for  high pressure over Scandi  

Indeed @weirpigThat's no doubt the case! The MO won't know how this is going to pan out following the SSW at the surface for our little island, in-fact nobody does! 

I'm just going to enjoy the ride!

Anyone know what time the Berlin charts update?

 

[bobbydog]

3 minutes ago, Iceaxecrampon said:

.......In other words In January it's possibly going to get a little bit colder?

 

[Paul]

We're going to run a competition this afternoon with the winners getting special pre-Xmas thread bans, woohoo!!

To win, those who keep posting solely about Met Office forecasts and the like with scary regularity, despite various requests to stop and the big notice at the top of every page in here, just have to keep doing it. Good luck to all those taking part  

Edited December 19, 2018 by Paul

[Weathizard]

We are pinning our hopes on the SSW but SSW don’t always deliver for us far from it infact - the models are pretty dire at the moment if you want cold and snow, there’s no sign of anything significant in the ensembles either and the MO update points to the fact their models have swung away from a quick response to the SSW in early January/late December as was pointed to a few days ago.

We are going to need to be very patient on this on I feel and let’s hope the SSW delivers something, at least we look to be in for a break from the SWrly barrage of hideous weather we’ve had just lately with high pressure starting to dominate, albeit could be a cloudy one.

[CanadaAl]

I'm honestly happy with a HP Xmas followed by cooling down into early Jan. Sick of this rain. 

Edit: Xmas chart

Edited December 19, 2018 by CanadaAl

[Snowy L]

42 minutes ago, Team Jo said:

Just reposting this in case folks missed it upthread for those knee jerking about snowmageddon not being shown on the current outputs.

I think model fatigue might have set in a little bit, if you are hanging off every single run I really, really recommend taking a break, else you will drive yourself loopy examining every nuance of every frame. 

Panic not! Lots happening, be patient!

This, personally I would wait at least a week until the initial displacement of the vortex happening is factored into the models at the starting point at least. At the moment, the models have the vortex over Greenland (correct as of now), but they continue to see it there, GFS in particular sticking with this throughout its runs.

[Met4Cast]

A surge of Westerlies across the Pacific should drive a rise in angular momentum over the next week or so encouraging ridging Northwards towards the pole, coinciding with the SSW there's a lot to be excited for.

NWP models whilst not showing anything exciting at the moment WILL change to show something more akin to what many in here are waiting for.. a little patience, the reward is coming.

[karlos1983]

Nothing dramatic showing on the AO/NAO yet, although a split in direction on the NAO at the end of the period

[bobbydog]

Only just looked at the panel GEFS.

There's some crackers in there at the end of the run!

It seems at least the ensembles are picking up on major changes...

[East_England_Stormchaser91]

3 hours ago, IDO said:

Very mild uppers for western Europe and even further east as we move past Christmas:

Not sure where the MetOffice is getting this easterly from as I don't see an obvious route from a trop led pattern?

The problem we have is in this holding pattern we have, we are giving the strat PV plenty of time to get its act together, making trop led help for any downwelling rather unhelpful:

That PV is not what we want to see? Any attempt to ridge from wave 1 Atlantic pushes meet a stubborn PV to our north! All this will seemingly do (till we get the mid-Jan SSW input) is enforce that UK Block. As I have been thinking, the SSW is going to be make or break for UK cold as the current repeating pattern remains bad for the UK cold picture.

Every cloud has its silver lining.

At least if we do get a cold shot with the SSW protruding down into the lower levels, the cold has been locked in and not watered down from previous heights draining it away. So it should have some brutality behind it if we do get lucky, like back in February. 

[ITSY]

For those losing faith, a couple of Northern Hemisphere charts for January: 

First, the MJO analog prediction (forecast based on MJO tendency in Pacific):  

 

Second, the CFS geopotential heights forecast based primarily on stratosphere (up above): 

 

None of this proves we will go cold but it indicates that the overwhelmingly favoured outcome (on basis of oceanic, tropical and stratospheric factors to name a few) is exactly that. (Although, granted, the MJO analog could go either way for us given exact location of SE Europe heights but that's detail beyond the realm of these predictions). Watch this space

Edited December 19, 2018 by ITSY

[Methuselah]

With all this talk of an SSW, I suddenly shaved my head, today...the tropospheric response was immediate!

[Nick F]

1 hour ago, Snowy L said:

This, personally I would wait at least a week until the initial displacement of the vortex happening is factored into the models at the starting point at least. At the moment, the models have the vortex over Greenland (correct as of now), but they continue to see it there, GFS in particular sticking with this throughout its runs.

Until any down-welling from warming of the polar stratosphere / reversal to easterly occurs and where, the models will carry on working with the effects of the current background weak El Nino state - which I have read usually features more variable fluctuations in the upper flow than a stronger El Nino event, with spells of more zonal momentum followed by more meridional / amplifying trough-ridge spells, these alternating spells of zonal/meridional are also linked to which part of the MJO cycle we are in. 

A flurry of tweets in twitterland from those in the know this afternoon that are increasingly reinforcing the likelihood of a SSW / SPV split late this month or early Jan,

but be aware that where it manifests itself it can take around 20 days for downward propagation into the troposphere, so it may not be until mid-Jan onwards we see its effects if the downwelling places favourably. However, before then, we may see some help from the MJO cycle (don't rely on the RMM plots use VP200) going back through colder phases early Jan plus El Nino forcing - or it will help reinforce high latitude blocking in tandem with stratospsheric downwelling when it occurs.

Edited December 19, 2018 by Nick F

[northwestsnow]

Thanks Nick for that interesting post

For now it would seem the best we can hope for is a sceuro high, hopefully the 12zs will drag any high pressure at a northerly enough latitude to at least bring some more seasonal conditions on the ground over Xmas..

Zonal winds still progged to drop away as far as i am aware, although i haven't seen Mike Poole post the latest in that regard to day ..

hope Paul doesn't mind but i just watched a fascinating forecast by Matt Taylor on the beeb, mainly about the SSW and the potential for significant cold as we go through January.:-)

Edited December 19, 2018 by northwestsnow

[Kirkcaldy Weather]

4 minutes ago, northwestsnow said:

Thanks Nick for that interesting post

For now it would seem the best we can hope for is a sceuro high, hopefully the 12zs will drag any high pressure at a northerly enough latitude to at least bring some more seasonal conditions on the ground over Xmas..

Zonal winds still progged to drop away as far as i am aware, although i haven't seen Mike Poole post the latest in that regard to day ..

these the charts you are looking for mate? 

 

[northwestsnow]

1 minute ago, Kirkcaldy Weather said:

these the charts you are looking for mate? 

 

Yes, thats the one, thank you

[Mike Poole]

19 minutes ago, northwestsnow said:

Thanks Nick for that interesting post

For now it would seem the best we can hope for is a sceuro high, hopefully the 12zs will drag any high pressure at a northerly enough latitude to at least bring some more seasonal conditions on the ground over Xmas..

Zonal winds still progged to drop away as far as i am aware, although i haven't seen Mike Poole post the latest in that regard to day ..

hope Paul doesn't mind but i just watched a fascinating forecast by Matt Taylor on the beeb, mainly about the SSW and the potential for significant cold as we go through January.:-)

Here it is, GEFS take anyway, all going for reversal 25th to 26th:

And the mean is trending well negative after.  Good to see the ECM on board with this now.

All good as far as I'm concerned today!

Edited December 19, 2018 by Mike Poole

[Frosty.]

Confidence in a marked change to colder weather in January seems to be decreasing and being shunted further back..not a good sign!..meanwhile the Gfs 6z operational shows no sign of anything wintry, plenty of high pressure eventually but temps close to average so probably a lot of cloud around meaning limited amounts of frost / fog and probably staying more changeable across the north, especially the far n / nw.

[Tim Bland]

1 hour ago, Daniel Smith said:

A surge of Westerlies across the Pacific should drive a rise in angular momentum over the next week or so encouraging ridging Northwards towards the pole, coinciding with the SSW there's a lot to be excited for.

NWP models whilst not showing anything exciting at the moment WILL change to show something more akin to what many in here are waiting for.. a little patience, the reward is coming.

No offence mate but you were saying (on a daily basis) a few weeks ago that the change to cold WILL happen around 15th dec. There is no guarantee that AM or. SSW will definitely deliver cold and snow and anyone who says otherwise is misleading people. Eventually there will be a cold spell and hopefully The SSW will help deliver this in Jan but there are no guarantees.

[bluearmy]

3 minutes ago, Frosty. said:

Confidence in a marked change to colder weather in January seems to be decreasing and being shunted further back..not a good sign!..meanwhile the Gfs 6z operational shows no sign of anything wintry, plenty of high pressure eventually but temps close to average so probably a lot of cloud around meaning limited amounts of frost / fog and probably staying more changeable across the north, especially the far n / nw.

Karl - I think a lot of this is based on one Exeter update - I wouldn’t be making any assumptions until fri/sat issue after the next ec 46 has been digested 

In the meantime, we have a big warming and a marked slowing of the zonal winds high up approaching fast - it’s  more than feasible that the modelling will catch up with this once it’s under way 

[Met4Cast]

5 minutes ago, Tim Bland said:

No offence mate but you were saying (on a daily basis) a few weeks ago that the change to cold WILL happen around 15th dec. There is no guarantee that AM or. SSW will definitely deliver cold and snow and anyone who says otherwise is misleading people. Eventually there will be a cold spell and hopefully The SSW will help deliver this in Jan but there are no guarantees.

We saw a mid-month cold spell.. blocking did materialise, in fact it was such a strong block the high was showing up on Stratospheric charts, rather rare for a block to that extent to develop across Scandinavia. 

It wasn't as long lasting/cold as perhaps expected but the general pattern was pretty spot on as was the timing.

Edited December 19, 2018 by Daniel Smith

[frosty ground]

Much milder run from the ICON... Block shunted east

[Tim Bland]

4 minutes ago, Daniel Smith said:

We saw a mid-month cold spell.. blocking did materialise, in fact it was such a strong block the high was showing up on Stratospheric charts, rather rare for a block to that extent to develop across Scandinavia. 

It wasn't as long lasting/cold as perhaps expected but the general pattern was pretty spot on as was the timing.

Most places hardly had a frost and almost no one had snow, so for December I wouldn’t call last week a cold spell

[Met4Cast]

3 minutes ago, Tim Bland said:

Most places hardly had a frost and almost no one had snow, so for December I wouldn’t call last week a cold spell

You wouldn't call a week of below average temperatures and uppers of -10c a "cold spell"? Just because you personally may not have seen snow, many people in the North did along with quite a freezing rain event for some areas, too. 

The lack of widespread snowfall doesn't mean it wasn't a cold spell, when it quite categorically was.