Model output discussion 24/01/21

[carinthian]

2 minutes ago, Severe Siberian icy blast said:

You tease so they expect the gem to be along the right lines? 

We've already saw how stubborn the cold can be, these weak heights are hard to model, I'm quite hopefull about the 12z, remember of course anything past 120 atm is just for fun, unless it shows cold and snow then it's picked up on the obvious pattern

Hi, no but very uncertain post weekend. However , the British winter so far seems to be chasing the mild rather than the cold, if you know what I mean. 

C

[MATTWOLVES 3]

There is quite a downbeat mood in here again this morning..save yourself some stress folks..things will look better before much longer..I think Lockdown is affecting many of us..but if we can get through this past year like we have,then I'm sure we can deal with a few days of bad model output.

The milder conditions that are coming could be a signal of MJO move and Nina forcing,it could also be the first signs of the SPV regaining some strength with temps dropping over the pole for the first time in a long time. Models may be latching onto this..But its looking a good call for a further warming event and perhaps another reversal to come,so that Vortex is not going to be getting much time to recover...I would say interesting times into the first week of February again..keep the faith folks.its not all bad..

Thanks to Marco P for putting up the graphs.

Edited January 26, 2021 by MATTWOLVES

[cyclonic happiness]

1 hour ago, IDO said:

Never say never with weather, but the trend is your friend, or not in this case, and with only gem and a handful of gefs now pointing in that direction with T-5days, I am doubtful. There is a good chance we may get another stalling front at the weekend before the Atlantic rolls in so fingers crossed for that boundary for some temporary snow?

I am still sitting firmly on the fence as to after the Atlantic trough has emptied east/SE. The gfs op 06z is probably the favourite:

The UK (south) relying on scraps and just not cold enough uppers for anything too interesting. The north and elevation will enjoy that NW'ly flow.

They said that about the last lots of snow that's still mostly still here, the uppers were mediocre at best, but we had the best snowfall in 3 years here.

[IDO]

6 minutes ago, cyclonic happiness said:

They said that about the last lots of snow that's still mostly still here, the uppers were mediocre at best, but we had the best snowfall in 3 years here.

Yes, 404 feet above sea-level mitigates the uppers a bit. Even at sea-level we had a couple of hours but most of it melted after the snow passed through.

Still a lot of spread post-d8 but general theme is cool to colder in London for 850s:

Very similar to what has come before (IMBY)...

Edited January 26, 2021 by IDO

[SqueakheartLW]

Who needs a beasterly to get any snow. Just take a look at GFS 06z ensemble Member 14 at 384 hours

Time to bring on the polar opposite, the BESTERLY

Before you think your eyes are deceiving you. That is uppers of -10 at 850hpa from the west covering most of England with -12 uppers over SE England

Edited January 26, 2021 by SqueakheartLW

[MJB]

Geared up for a climb down in temps at the start of Feb , quite a few members between -5 and -10 

[nick sussex]

Encouraging to see the GFS 06 hrs run moving to more trough disruption so more chances of some frontal snow at the weekend and I’m sure the current saga still has some way to run.

[Frigid]

10 minutes ago, SqueakheartLW said:

Who needs a beasterly to get any snow. Just take a look at GFS 06z ensemble Member 14 at 384 hours

Time to bring on the polar opposite, the BESTERLY

Before you think your eyes are deceiving you. That is uppers of -10 at 850hpa from the west covering most of England with -12 uppers over SE England

Westerlies giving -10c 850hpa temps. I just know if that came off we would be buried in snow!

[danthetan]

51 minutes ago, MATTWOLVES said:

There is quite a downbeat mood in here again this morning..save yourself some stress folks..things will look better before much longer..I think Lockdown is affecting many of us..but if we can get through this past year like we have,then I'm sure we can deal with a few days of bad model output.

The milder conditions that are coming could be a signal of MJO move and Nina forcing,it could also be the first signs of the SPV regaining some strength with temps dropping over the pole for the first time in a long time. Models may be latching onto this..But its looking a good call for a further warming event and perhaps another reversal to come,so that Vortex is not going to be getting much time to recover...I would say interesting times into the first week of February again..keep the faith folks.its not all bad..

Thanks to Marco P for putting up the graphs.

With the SPV +12m/s westerly ATM  is this why the models keep pushing through the Atlantic with a strong jet. With a steep drop off of the SPV imminent perhaps this will help keeping back the Atlantic and disrupt the jet. 

[feb1991blizzard]

9 minutes ago, Frigid said:

Westerlies giving -10c 850hpa temps. I just know if that came off we would be buried in snow!

Problem is they don't last, apart from the 17th Dec 2010 but that was a wind veering westerly in an overall huge Arctic airmass, the Westerly PM airmasses tend to have mild sectors in them, they don't even deliver for Saddleworth so what chance for Manchester, Liverpool and Preston etc

[masheeuk]

50 minutes ago, Frigid said:

Westerlies giving -10c 850hpa temps. I just know if that came off we would be buried in snow!

Oh yes please

[MATTWOLVES 3]

What we all need while in a miserable lockdown is some out there Gfs Snow graphs..firstly on Sunday,all be it transient..but it could disrupt and slow down..further chances along the line surely!! Its been that kind of Winter..me,I'm as happy as a pig in dung.

[tight isobar]

1 hour ago, nick sussex said:

Encouraging to see the GFS 06 hrs run moving to more trough disruption so more chances of some frontal snow at the weekend and I’m sure the current saga still has some way to run.

A proper all=\nothing situation this coming weekend...should the ebb n flow fall correctly...the past weekend snow event...Will have it's nose put

right out of joint....@NOTABLE...

[Tamara]

Posted by chionomaniac last Saturday:

Just reading through your post, and the one thing that I notice is that despite the drop in GLAAM, and a reduction of the more Nino-ish December response, we have yet to see a traditional Nina H500 pattern to develop. I suspect that we have to grateful for the SSW for that - not only for well recognised polar and mid latitude responses, but also the feedback indirectly to tropical regions. I know that there are those who are far more qualified to put more meat on the bones regarding this than me and there have been a number of papers on this in the last few years, but it is another wild card thrown into the equation.

And, if you had to, and your life depended on it, what would your punt for February be? After all, you have spent years on research of mid latitude responses to tropical forcing, it would be great to see the end product of what you consider more likely. One of the reasons, that I suspect you don’t or can’t ( you are not alone) is the lack of forecast data in this field. This would help a lot. When looking at the data, it is recording what has already occurred and the MJO forecasts are reliably unreliable. This makes commentary on what has happened far easier than being able to predict in the mid range. 

I think that the sooner that we can get more pieces in this jigsaw, the better.

-------------------------------------------------------------------------------------------------------------------------

 

The H500 pattern has been very consistent with a Nina response. The crucial aspect, as you allude to, is that it is a Nina response in tandem with a disrupted stratospheric profile. 

At least a couple of previous posts have commented on the upstream pattern switch to Aleutian heights in response to the GWO moving into the Nina attractor phases heading into the second third of winter. The GWO, phase depiction of global wind-flow within the tropics and extra tropics, being a precise barometer of tropical>extra tropical pattern response on hemispheric levels.

Amplification within the Pacific, very characteristic of La Nina signature, pushes inertia into the downstream polar jet, which is exactly what we have seen. However, the disjointed zonal wind anomaly within the polar field, leading to very weak and erratic flow, has meant that the usual (traditional) downstream response of jet stream flow has been rather blockaded with the result of southward and equally fractured flow rather than the flatter zonal flow across the North Atlantic seen under a more traditional response. Hence the shallow tropospheric 'cold' ridges that have disrupted low pressure systems in the way that has been seen. Nonetheless, there has still been just enough inertia to keep the pattern relatively flat and 'faster' than under a more meridional downstream Nino-esque regime

As the response to a post below also suggests, this diffuse stratospheric>tropospheric response is not new, and was seen to an extent following the SSW of late January 2009 - during February 2009. There were very strident immediate expectations following that particular SSW, but the combination of La Nina and w/QBO at that particular time of the solar cycle provided a much more diffuse tropospheric response than the  subsequent bookend part of the year which saw a classic Nina-esque stratospheric pathway during Dec/Jan/Fed 2009/10. Indeed, the response to the SSW of Jan 2010 was a more 'classic' cold pattern response than that of a year previously. The first part of the season was troposphere>lower stratosphere led (and actually the deepest cold weather of the season) before the upper part of the stratosphere warmed considerably and maintained the unstable (cold pattern) tropospheric pattern of the first part of the winter.

I think for the weather pattern observer those two seasons, a decade back, is a reasonable case study that gives some clues as to the manifestation of this winter (but with further added climate forcing another 10 yrs on - though that is not for this thread) That is the closest I would get to any 'punt' And for good reason, quite apart from not having the same weather preference motivation for specific weather type as most other.

With  all that in mind, and notwithstanding the credible correlations of the comparisons  - one thing that has been learned over years passed -  is there is no one size fits all response and each situation/pattern/set of variables have to be taken on their own merits. That also leaves making 'punts' a little redundant from my point of view. Whilst not a forecaster (and just one of many reasons not to be) is that analogue pattern matching, however unintentionally, tends to be skewed by bias confirmation as well as the added superimposed forcing on the climate which has distorted feedbacks, year on year, across the tropics>extra tropics and at the pole.  However, the GSDM still remains a highly worthwhile aid to diagnosing the vicissitudes of numerical modelling and the inherent biases of these models. What you get with a global wind-flow budget remains a precise measure of inertia within the hemispheres at any given time, which inclusively calculates the superimposed forcing that is almost insidiously being added year on year.

One good reason why so many tropical (MJO) and extra tropical (GWO) phase composites need to be readily updated as a perpetual 'work in progress' to take account of pattern responses according to the ever more volatile wind-flow profiles according to progressive broadscale warming trends.

 

2 hours ago, winterof79 said:

Any thoughts on Matt Hugos comments /gifs and trends? 

Its that stuck record once more but any comments related to trends have to take into account all probabilistic outcomes and not just the one that human intervention would like to steer towards.  As stated above, recent summaries have commented on the diffuse weaker than average westerly gradient of this season and, stripping away all the repeated detail and analysis, the likely outcomes as being a N/S or NE/SW divide. That suggestion has continued to play out and remains well advertised in the further outlook. - if one takes out the usual speculative outputs that tend to catch the eye on this thread and are given maximum exposure  The disjointed and rather unstable polar profile should continue to steer low pressure systems on a more southerly track and invite some cold air advection in their wake, with more northern latitudes seeing these the most. However, the continued expectation for the MJO to be a magic bullet to a definitive  sustained cold block requires greater objectivity as (keeps being repeated) it is not as straightforward as x ingredient = one specific y outcome.

There is no doubt that the La Nina-esque atmospheric profile that has taken over since the end of the first third of this season is assisting the diffused tropospheric response seen similarly on occasions such as February 2009, when the combination of robust tropical forcing lead to equally strong extra tropical +mountain torques inducing a highly significant SSW (when viewed under w/QBO and La Nina profile). There are some similarities, at least, to that time - and the context of the upcoming pattern phase should be viewed with a similar perspective - and that includes the sort of initial blocking responses as seen early in Feb 2009 which, (at least for those disposed to deep freezes) appeared to offer much but actually in terms of longevity fell a long way short. This suggests there certainly IS wintry potential for the UK looking ahead into February, but this is set against a profile that is rather working against the sort of prolonged and sustained very cold spell that might be achieved otherwise.   Equally however there remains other outcomes which will likely not get coverage on this thread.

That is about as off the fence I would, realistically, and equally reluctantly want to move. So, yes, not very much off the fence at all then.....From a (boringly) neutral  and very detached perspective I am far, far more interested in the overview than a specific weather outcome.

 

[northwestsnow]

Worth  noting quite a wintry update from Exeter before the 12zs come out.

They seem quite bullish about HP to our North as we exit the first week of Feb so perhaps something to look for ,we certainly need upgrades ...

Hopefully.....

[offerman]

1 hour ago, MATTWOLVES said:

What we all need while in a miserable lockdown is some out there Gfs Snow graphs..firstly on Sunday,all be it transient..but it could disrupt and slow down..further chances along the line surely!! Its been that kind of Winter..me,I'm as happy as a pig in dung.

When I look at the morning runs nothing was indicative as these snow graphics you show .  Will have to look at latest runs . Couldn’t see any 850s -5 over us down here in southwest yet snow shows on your graphics 

weather looks quite zonal comping up 

 

[Griff]

18 minutes ago, Tamara said:

This suggests there certainly IS wintry potential for the UK looking ahead into February, but this is set against a profile that is rather working against the sort of prolonged and sustained very cold spell that might be achieved otherwise.   Equally however there remains other outcomes which will likely not get coverage on this thread.

Excellent and informative as always, but here in lies the problem for the 'average member' (sorry I can't help myself sometimes), if the most knowledgeable, and best informed can't say definitively, acknowledging how complex the set up is, what chance for the rest of us? Anyone proclaiming the end of winter, or nailed on 'booms' beware!  

Thanks Tamara, TLDR we all should keep watching, chill a little and enjoy whatever nature might throw at us

Edited January 26, 2021 by Griff

[Bricriu]

14 minutes ago, sebastiaan1973 said:

Thanks Tamara. After a couple of days February 2009 delivered nothing special. So no prolonged, very cold weather this winter 

Her thoughts mirror what the UKMO have been saying all along.  The cold air makes it further south at times before retreating northwards again. Hopefully in this setup it will be quite snowy at times over a wide area during the next month.

Edited January 26, 2021 by Bricriu

[MATTWOLVES 3]

The post i was just going to replie to which asked Tamara...(so no long lived cold snap)seems to have been removed. Tamara states the possibility going forward is there,but does not want to issue  a forecast for February...which Is basically sensible,there is a lot going on with both the Strat and the Pacific.. Im pretty confident the last warming on January 5th is at least partly responsible for some of the snow events that have been witnessed recently. With a further warming due we could be looking at a similar scenario again as we move into February...if a split were to occur we could get a much more significant cold blast.. or its possible nothing at all. 

So its possible two major impacters of our conditions,namely the Pacific and the strat will be tussling for the rights to boss our conditions over the coming weeks.To sum that up in a nutshell will most like equate to Model volatility. Who would be a forecaster at this present time!.

Edited January 26, 2021 by MATTWOLVES

[Paul]

At closer range, the rain is looking a real concern again this week. The UKV 12z has ramped up the totals a bit, with weds into thurs looking very wet again. 

The other issue is that not all of that precip is going to be rain.. Snow depths of 30cm or so are likely over the high ground by Thursday afternoon. 

All thanks to another really strong temperature gradient, a lot like we saw last week - temperatures in low single figures or below freezing on one side of the front, double figures on the other.

 

[Methuselah]

4 minutes ago, MATTWOLVES said:

The post i was just going to replie to which asked Tamara...so no long lived cold snap seems to have been removed. Tamara states the possibility going forward is there,but does not want to issue  a forecast for February...which Is basically sensible,there is a lot going on with both the Strat and the Pacific.. Im pretty confident the last warming on January 5th is at least partly responsible for some of the snow events that have been witnessed recently. With a further warming due we could be looking at a similar scenario again as we move into February...if a split were to occur we could get a much more significant cold blast.. or its possible nothing at all. 

So its possible to major impacters of our conditions,namely the Pacific and the strat will be tussling for the rights to boss our conditions over the coming weeks.To sum that up in a nutshell will most like equate to Model volatility. Who would be a forecaster at this present time!.

Hi Matt, good post; with which I agree!

It may only be me, but where does Tamara deny the possibility of an extended outbreak of cold, snowy weather? IMO, she's diagnosing the current atmosphere as it is, and postulating about how it might develop? I do suspect that a few folks (not you, by the way) are trying to distill Tams's posts into eye-catching one-liners...?

My usual caveat -- I might well be talking utter shi'ite -- applies!

[Bricriu]

7 minutes ago, General Cluster said:

Hi Matt, good post; with which I agree!

It may only be me, but where does Tamara deny the possibility of an extended outbreak of cold, snowy weather? IMO, she's diagnosing the current atmosphere as it is, and postulating about how it might develop? I do suspect that a few folks (not you, by the way) are trying to distill Tams's posts into eye-catching one-liners...?

My usual caveat -- I might well be talking utter shi'ite -- applies!

I maybe wrong, but I read it as she has enough experience to know that you can never be certain of any one outcome, but if pushed she favours la nina, while not giving a  typical flat profile, acting as  enough of a spoiler to any prolonged cold spell in the UK.

Edited January 26, 2021 by Bricriu

[MJB]

42 minutes ago, offerman said:

When I look at the morning runs nothing was indicative as these snow graphics you show .  Will have to look at latest runs . Couldn’t see any 850s -5 over us down here in southwest yet snow shows on your graphics 

weather looks quite zonal comping up 

 

Apart from this 

Snow crossing the UK

[Methuselah]

Anywho, with fronts stalling over Scotty, this winter really does remind me of a typical 1960s (1963's ridiculous anomaly notwithstanding) winter:

    

All we need now is a wee bit of luck!

Edited January 26, 2021 by General Cluster

[Matt H]

ICON 12z looks like it might be going for the snow event on Sunday. Certainly looks positive out to t120.