Model Output Discussion - Christmas week and beyond

[IDO]

1 minute ago, Weather-history said:

Manchester 2m ECM temps

Shows the dip into Boxing Day but look at the difference around the 29th-30th.

Why is ECM producing these outliers in that timeframe against its ensembles? Something is outer of kilter, its happening too often. 

I have been banging on for years that the ECM op at D8-D10, in the winter especially, are not really of much value. Switch to the mean for longer range. So comments on D8+ ECM looking "promising" is a waste of internet traffic more often than not.

The ECM mean to D10 looks very flat:

 

[Weather-history]

13 minutes ago, IDO said:

 

The ECM mean to D10 looks very flat:

 

Is it flat or Atlantic trough? Whatever its not wintry

[IDO]

6 minutes ago, Weather-history said:

Is it flat or Atlantic trough? Whatever its not wintry

...my POV was from the UK. But there is a mini sine wave effect (loco zonal!) going on, so trough to ridge to trough, what you would expect even with a westerly flat pattern. The ens for London for pressure:

[Vikos]

12 minutes ago, Weather-history said:

Is it flat or Atlantic trough? Whatever its not wintry

Whatever it is, it will be boring af for the next 2 weeks. Time to focus on other things…

[Penicuikblizzard]

I’m really surprised that people are shocked about the milder solutions showing up now, La Niña winters tend to be front loaded so very much expecting the rest of this winter to be milder with transitional cold snaps 

Edited December 21, 2022 by Penicuikblizzard

[nick sussex]

When things go pearshaped they really go for the gold medal in the UK !

The upstream pattern has become flatter and flatter  and any cold turns into a blip.

The GFS still hangs onto better heights to the nw but even if that miraculously was correct it’s still a hard slog for the cold as low heights keep feeding low pressure near the UK.

[Nick F]

Probably best not to concentrate too much on what the models are showing towards New Year, some quite notable differences between GFS and EC on placements of lows and wedges of high pressure Boxing Day to New Year. Not sure whether to trust GFS's Greenland upper high wedge floating down across Iceland idea. Though into the New Year it does seem the models are agreeing on the broadscale patterns becoming increasingly hostile to sustained cold or even brief cold as the TPV begins to wrap up over the arctic circle. But this less palatable picture may change as we draw nearer, but wouldn't hold breath as seem plausible given what's going on upstream and MJO.

In the shorter term, there are modelling differences appearing as early as Christmas Day and these become more noticeable by Boxing Day. Still some model uncertainty for Christmas Day, but the models seem to be converging on the idea that it won’t be white Christmas Day for most. A fairly deep area of low pressure to the west of Ireland to start the weekend is forecast to move northeast past or over northern Scotland on Christmas Day, it does look to turn colder from the west across northern areas on GFS, cold enough to perhaps allow showers to fall as snow across northern and western Scotland and perhaps higher ground elsewhere in the north later in the day. EC delays the cold getting in until late evening / Xmas night, as it keeps a secondary low to the southwest, delaying the cold air.

EC 25th noon                                          GFS 25th noon

Great deal of uncertainty by Boxing Day with regards to an area of low pressure over the Bay of Biscay that looks to track northeast towards and over parts of England and Wales during the day. 00z ECMWF tracks the low northeast further south than 00z GFS, across SE England first thing Monday morning. Whereas GFS takes the low northeast across Wales, Midlands and exits over North Sea near the Humber and during the day. EC all rain across SE England, SE Midlands and East Anglia before clearing by 9am. GFS takes outbreaks of rain north across much of England and Wales but also turns it to snow across from Wales and Midlands northwwards.

Edited December 21, 2022 by Nick F

[Empire Of Snow]

5 minutes ago, Penicuikblizzard said:

I really surprised that people are shocked about the milder solutions showing up now, La Niña winters tend to be front loaded so very much expecting the rest of this winter to be milder with transitional cold snaps 

There've been cold La Nina winters. If you know today 21st December that it will be milder with just cold snaps until 1st March you can publish it and make some money. 

I might also start making forecasts using the phase of the moon. 

 

[Lukesluckybunch]

The UKMO at 168 is probably about the worse chart for UK cold..Icelandic lows,and a big area of high pressure to the South and southwest resulting in a very mild southwest flow!

[Mike Poole]

Probably time to take a back seat for a while, as keeping up with every run is quite time consuming!  The model output is not that great at the moment to be honest.

Today’s clusters T192-T240:

Cluster 3 has some weak heights over Greenland and removes euro high, clusters 1 and 4 in scandi - the other destination to link the euro high, so something to watch there.  Cluster 2 looks dire.

T264+

While the majority cluster is +NAO, there is blocking on the other two, cluster 2 with the heights in scandi or Russia.  So for me the jury is still out on the extent to which the strat and trop have coupled.  It would be useful to know this for certain either way, though.  

As an aside, probably as well I had an early night yesterday and missed that ‘zonality’ discussion, as it is a pet hate .  For me, it is quite straightforward.  The word ‘zonality’ does not exist.  Simples.  Look it up in a dictionary.  Zonal means relating to a zone (in our case, of latitude).  Zonal flow doesn’t have to be west to east, although for our weather, it usually is.  But we regularly post and talk about the stratosphere zonal winds chart (zonal component of wind at 60N).  That can be negative, i.e. east to west, after a SSW, or, indeed, through the entirety of summer.  

[feb1991blizzard]

3 minutes ago, Empire Of Snow said:

There've been cold La Nina winters. If you know today 21st December that it will be milder with just cold snaps until 1st March you can publish it and make some money. 

I might also start making forecasts using the phase of the moon. 

 

yes - 2018 - sting in tail - nina - coldest month since i was born - feb 1986 - on the nina side of enso neutral.

[northwestsnow]

EC big outlier Xmas day / Boxing day.

There is hope yet

[Stuie]

looking at the whole GEFS control Jet stream suite, hard to look past zonal until the end.

That is based on it`s 0z run.

[ANYWEATHER]

Looks like a green Christmas for many ,although the gfs throws in some complications for some stuff over the Christmas period, plenty of time for more winter to come, although I must admit I've had my snow fix for now

[bluearmy]

4 hours ago, geordiekev said:

Just wondering if the teleconnections predicted the US monster cold push, as seems to came out of the blue & has ramifications obviously downstream. Odd how climate change touted by a few for our European heights, continuously fail to mention why US consistently year after year have these deep cold troughs.

Would have thought there's something causing these exceptional frigid US conditions but yet to have an answer.

All to play for whilst the monster forms

Joe B has been banging on for weeks about the retrogressive ridge. Basically, when the ridges go up over a couple of areas of the polar field (inc scandi) a retrogressive pattern follows over the following three weeks or so that works scandi/greeny/e Canada /Alaska and finally Siberia. It’s not necessarily the same ridge (though it can be if clean retrogression).  Anyway, we’ve seen this play out and it continues to do so. An Arctic blast into the states was expected as the pattern worked west. Of course this final blast has worked out to be brutally cold as the Alaskan ridge went into overdrive but it’s not going to last much longer as next week is predicted to be mild across the whole continent.

 

31 minutes ago, CreweCold said:

Not a bad 9&10 day chart from ECM actually. I suspect people like Chiono et al will know why

the gfs strat charts continue to show an easing off of the zonal flow higher up as week 2 progresses into week 3. Back towards average values. The ramifications in the lower trop are a connect to the southern arm of the jet in a weeks time around 60N which then restricts south to be between 30 and 50 N but even that looks like being cut by day 16-20.  so we may well be looking at a coupe of weeks of mobility with some amplification still around - the e Canadian high anomoly looks solid on the eps but we also struggle to remove euro heights. There are plenty of indications of scandi or sceuro ridges working around which will obviously help to drive waves up into the strat in association with the Aleutian troughing.  It’s not very encouraging but then we should also be a little open minded about possible changes showing up later in week 2 if the MJO amplifies a bit more into 7/8. 

[joggs]

Think we've being led up the garden path by the models re, cold spell Xmas,new year. Things now coming into line of a flatter pattern. Just shows that 90%(maybe more) of the time, we're just not destined for prolonged cold and snow. Climate change? 

Anyway,time for a break. Meto must be seeing something later in Jan....

Have a great Xmas all.

[Penrith Snow]

1 hour ago, mb018538 said:

I know it's not the UK, but look at this chart from the USA in the coming days. 850 temps below -30 at latitudes further south than the UK 
Already seen -52c in Canada, and likely to be some records broken in places. Parts of the Dakotas/Montana etc will see temps below -35c.

Yes of course, US in the Freezer, Western Europe in the Sauna and a Athens Snowfall Special, 21st Century Winters are soooo predictable!

Andy

[Bristawl Si]

3 minutes ago, joggs said:

Think we've being led up the garden path by the models re, cold spell Xmas,new year. Things now coming into line of a flatter pattern. Just shows that 90%(maybe more) of the time, we're just not destined for prolonged cold and snow. Climate change? 

Nope.

Maritime climate, facing the Atlantic. Default weather pattern for a UK Winter.

[LetItSnow!]

To be honest, I’ve remained open-minded this whole time and I still am, but when I first started to see hints of the extreme cold in America I did start to become more open minded to the chance of a milder spell. It does seem that bitterly cold weather over there doesn’t bode well for us, particularly in recent times. The severe American winter of 2013/2014 sent the jet stream on steroids and we took the absolute brunt of it. Late-January 2019 and through February saw some record snow and cold… we know what happened. The remarkable cold wave of February 2021 tipped the scales once again and… we know what happened. December 2022… 
 

The only thing I can think of is that in the past cold winters could more easily co exist due to weaker heights to our south then. I imagine nowadays that with a stronger presence of high pressure to our south, the energy that is generated by cold air exiting into the Atlantic would have more easily lead to undercutting pre-1988; nowadays it perhaps fires up the jet stream and can pump up warm air from our southwest and inflate Euro heights. In the case of February 2021, maybe this was why the blocking collapsed spectacularly. And I’m not saying this didn’t happen before (February 1912, did a historic post on it, similar events occurred there after record cold in parts of the USA in the winter of 1911/1912), but seems we’re more prone to it going wrong now.

 

13 minutes ago, joggs said:

Think we've being led up the garden path by the models re, cold spell Xmas,new year. Things now coming into line of a flatter pattern. Just shows that 90%(maybe more) of the time, we're just not destined for prolonged cold and snow. Climate change? 

Anyway,time for a break. Meto must be seeing something later in Jan....

Have a great Xmas all.

This may answer your thoughts.

Edited December 21, 2022 by LetItSnow!

[Phil Blake]

Will I be the first to say we need a zonal reset  

[TEITS]

Im not as confident on the outlook as others on here. Look at the handling of the deep low pressure on the N America charts from +72 to +144 and then compare with the ramifications it has on the UK at +120 to +144. The GFS handles this low pressure very differently to all the other models and is the cause of the differences at this timeframe for the UK.

So im not suggesting a change to a prolonged, significant cold spell. However the scenario of a snow event is possible if the GFS is correct as it looks as though a low pressure may move N and bump into the colder air that has arrived over xmas.

 

[Anthony Burden]

34 minutes ago, Nick F said:

Probably best not to concentrate too much on what the models are showing towards New Year, some quite notable differences between GFS and EC on placements of lows and wedges of high pressure Boxing Day to New Year. Not sure whether to trust GFS's Greenland upper high wedge floating down across Iceland idea. Though into the New Year it does seem the models are agreeing on the broadscale patterns becoming increasingly hostile to sustained cold or even brief cold as the TPV begins to wrap up over the arctic circle. But this less palatable picture may change as we draw nearer, but wouldn't hold breath as seem plausible given what's going on upstream and MJO.

In the shorter term, there are modelling differences appearing as early as Christmas Day and these become more noticeable by Boxing Day. Still some model uncertainty for Christmas Day, but the models seem to be converging on the idea that it won’t be white Christmas Day for most. A fairly deep area of low pressure to the west of Ireland to start the weekend is forecast to move northeast past or over northern Scotland on Christmas Day, it does look to turn colder from the west across northern areas on GFS, cold enough to perhaps allow showers to fall as snow across northern and western Scotland and perhaps higher ground elsewhere in the north later in the day. EC delays the cold getting in until late evening / Xmas night, as it keeps a secondary low to the southwest, delaying the cold air.

EC 25th noon                                          GFS 25th noon

Great deal of uncertainty by Boxing Day with regards to an area of low pressure over the Bay of Biscay that looks to track northeast towards and over parts of England and Wales during the day. 00z ECMWF tracks the low northeast further south than 00z GFS, across SE England first thing Monday morning. Whereas GFS takes the low northeast across Wales, Midlands and exits over North Sea near the Humber and during the day. EC all rain across SE England, SE Midlands and East Anglia before clearing by 9am. GFS takes outbreaks of rain north across much of England and Wales but also turns it to snow across from Wales and Midlands northwwards.

Hi Nick,the idea of a Greenland high returning seems to have been dropped completely at present but as we know that can change in a flick of an eye.

[Ventnor Viking]

My highly technical analysis can be rounded up in to three words ....Mild and Miserable! 

Have a great Christmas everyone

[Lukesluckybunch]

Lets hope the 6z continues with that threat of snow boxing day..Midlands northwards was looking good in the 0z even my area had 1.7cm

Edited December 21, 2022 by Lukesluckybunch
Spelling

[Nick F]

11 minutes ago, Anthony Burden said:

Hi Nick,the idea of a Greenland high returning seems to have been dropped completely at present but as we know that can change in a flick of an eye.

GFS has been the only model keen to hold back over NE Canada the upper low / TPV that brings the Winter Storm to N America this week and thus pumps WAA to develop the Greenland Wedge. Even the other North American model GEM says no. So remain sceptical of GFS's love affair of the Greenland Wedge which is still there on the 00z op, albeit a shadow of what it was showing block-wise before.