Model Output Discussion - Into 2024

[ANYWEATHER]

18 minutes ago, Scott Ingham said:

It’s the start of a deep cold spell. How long? Not known yet but it will be the first real spell of this winter and one with building blocks in place with the potential to produce a fair amount of snow and ice days.

btw this was a date I threw out there nearly 3 weeks ago due to background signals that many have already gone through numerous times over this period. 
 

It was a best guess based on them with lag for impacts to hit nothing more but it’s a running joke as the models began to converge on this exact date and the chances of getting something like this correct 3 weeks out is low!

Could you please clarify , why you say it's the start of a deep cold spell ???

[IDO]

Better GFS to the west on this run. Can we get the higher pressure above the Azores cut-off low, and stop that spoiler delaying shortwave running across the western side of the UK high?

0z:  06z: 

[Lukesluckybunch]

I'm liking this..we seem to have the push into Greenland area at 132..come on!

[booferking]

Early on gfs strengthens the heights in Atlantic compared to this mornings run.

[frosty ground]

23 minutes ago, booferking said:

Sorry if you don't like what i say just hit the ignore button i just say what i see I'm taking the runs as face value and that's what i see hopefully ecm is sniffing up the wrong agenda and falls in line with gfs & gem.

That replay makes no sense, my comment to you was one of ignoring wedges nothing more

[Scott Ingham]

@TEITS is correct btw. In 2010 and 2009 the ecm went on one for 48 hours before quickly coming back to its 240 ideas at 120 and the rest is history! 
 

Just to add this latest gfs run is similar to ouput 48 hours ago! Heights are hugely different in a good way around Greenland. First signs of a climb back towards nirvana? 

[That ECM]

This may give us more of an idea where ukmo would have gone?

[IDO]

Better with that shortwave:

06z:  0z: 

Edited January 6 by IDO

[TSNWK]

Just now, That ECM said:

This may give us more of an idea where ukmo would have gone?

No annoying low south of Greenland at day 6

[BLAST FROM THE PAST]

7 minutes ago, Drifter said:

The trouble with the ECM is that northerly looks like it’s on borrowed time and would turn milder soon after. 

Look at the gfs, the 00z and 06z yesterday?  Then look where it’s returned to.  Like I said the other day, expect volatility from models on individual runs.  And the warming in the Strat is nicely on time…even if technically it isn’t a major SSW……I’m sure it will have ramifications 

 

BFTP

[Rob 79812010]

12 minutes ago, ANYWEATHER said:

Could you please clarify , why you say it's the start of a deep cold spell ???

I would say the start of a cold spell. Deep cold, doesn't seem that way

[booferking]

Just now, frosty ground said:

That replay makes no sense, my comment to you was one of ignoring wedges nothing more

The wedge would have failed like on control and alot faster but hopefully ecm barking up the wrong tree gfs coming out looking good early on 

[Duane S.]

1 hour ago, Polar Maritime said:

Still going up..

 

Stunning. As steep an ascent at this level that I can remember .

I find a better correlation to incoming cold however is at 30mb. Worth watching in the coming days. That said it’s already been running above average for 3 odd weeks, so that is definitely already playing to our advantage.

 

[IDO]

By T150 the difference that shortwave makes with energy into the Atlantic from the UK high:

0z:  06z: 

[Chesil View]

22 minutes ago, fromey said:

I ask Marco yesterday about this being a major warming and he replied 

But at what strength. 

[AO-]

At 156 GFS seems allright. The cold heading South with the through up north. Now see whether there is enough energy in the West to pump up the high towards Greenland. 

[Lukesluckybunch]

Here we go...this looks excellent and early!!heights disappearing over europe

[Polar Maritime]

2 minutes ago, Chesil View said:

But at what strength. 

Its not a major warming that will split the Vortex, But it is a strong one that displaces the PV.

Isn't this a fantastic winter for model  viewing, so much going off its hard to keep up with!

Edited January 6 by Polar Maritime

[keithlucky]

6 minutes ago, Man With Beard said:

It kind of feels wrong to post this on a day John Holmes of all people is bigging up the cold, but it must be mentioned that a really firm Greenland block signal doesn't last more than a few days on the ECM clusters - doesn't necessarily mean the end of cold and snow as the overall pattern remains pretty messed up beyond 17th January, but chances of a prolonged cold spell would be a bit more doubtful. Still, of course these are D11-D15 charts so much could change particularly in the absence of agreement.

Strat warming normally lasts a a couple of weeks,the very cold air will be pushed south across UK around 14th lasting until February .

[Ali1977]

Just now, Lukesluckybunch said:

Here we go...this looks excellent and early!!heights disappearing over europe

Agree, looks like a great run to now

[Scott Ingham]

On 04/01/2024 at 09:37, MattH said:

Hi.

I just wanted to create a post from an educational perspective and also be a point of reference regarding the importance of the GSDM and the AAM on the medium and long term. Hopefully, anyone who questions this should change their mind after reading the below. The reason it is worth doing this is because there is no better, clearer, example of the importance and connections between those upstream, Pacific developments and the downstream influence.

I'll attempt to highlight and stitch this together using some of the usual plots and charts which tell the story so very well indeed and it is this which, hopefully, helps people to at least better understand the influences of the GSDM and what to look for moving forward.

OVERVIEW: Firstly, we have just endured a very wet December, this comes as no surprise given what happened to the AAM in late November. Interestingly, seasonal models all pointed towards December being a +ve NAO month, in keeping with the long-term teleconnections with regard El Nino and a +IOD in early winter. The late Nov and early Dec cold spell can be linked back to the behaviour of the GSDM too, while what followed through much of December certainly can and what is happening now and looking ahead, most certainly is. Despite a weakened stratospheric polar vortex, it is the troposphere that is 'leading the dance' rather than the stratosphere for the most part even though it is lending a hand.

The late Nov/early Dec blocked pattern has links to the temporary rise in the AAM in mid-November, with the usual lag in place. We can see this first evolution in the below plots...

The second and more obvious evolution was then the more pronounced fall in AAM through late Nov as the MJO returned to the W Hem and westerly inertia was removed from the GSDM budget and, as usual, AAM fell along with a -FT (Frictional Torque) and -MT (Mountain Torque) event. The result was, as ever, propagation through the extra-tropics and then into the mid-latitudes of more westerly momentum, propped up by easterly momentum at circa 30-40N - Remember the inflated Azores high in the run-up to Christmas? - We can see how the +AAM anomalies, in particular, were distributed through the atmosphere within the usual window of approximately 14 days. No surprise we then saw an enhanced period of +AO and +NAO conditions just before mid-December onwards.

Lastly, comes the 'big event' within the last week or so in terms of the pronounced rise in AAM. Once again, in complete contrast to what happened through mid-November, with a lag of course, we can see how the marked rise in AAM has allowed the propagation through the sub-tropics and into the mid-latitudes of more easterly inertia (-AAM) very well indeed, this is particularly obvious on the relative AAM transports plot, as highlighted below. Once again, no surprises at all and of which has been documented by the usual few on the group we are now seeing a complete reversal of that +AO and +NAO period with an array of mid-latitude and, eventually, high latitude blocking patterns.

We can also see this visually on the zonal wind plots at 100hPa (top of the trop/bottom of the strat) too.

While like in many areas of meteorology, there is never often a usual "a+b=c evolution", but this is about as close to that as you can get. We have certainly had help from the stratosphere here mind because a robust stratospheric polar vortex that is downwelling westerly winds into the troposphere can often be the dominant player, overriding what has occurred over the last month. There is likely to be some 'help' here from the El Nino and eQBO combination this winter as the sPV continues to remain disorganised and far weaker than it can be at this point in the winter with far less influence on the troposphere too.

When it comes to the AAM it is crucial to be able to accept and acknowledge when there are other overriding influences and counterbalances. Tamara et al often talk about not taking the MJO at 'face value', it is similar with the AAM, but when you combine the usefulness of the GSDM and all it incorporates then, as I have perfectly examined here, nobody can ever say the likes of the GSDM and the AAM is "flawed or useless" when it comes to pre-empting NWP, at times, and also gauging how the broader patterns may evolve and shift.

As I mentioned at the start of the post, I wanted to put this one together because there is no better example of the usefulness of the GSDM than what has occurred over the last month or so. The evolution and 'story' of the atmosphere have been well played out in these plots.

For those who want some winter weather after the last few weeks of very wet conditions then 'this is your time'. We approach mid-winter with such solid footing for cold synoptics that it should be a pleasure to watch the more unusual patterns being modelled in NWP and, interestingly, this continues to link in well with the majority if not all of the seasonal models with regards to how Jan and Feb and perhaps even Mar should progress. Winter is about to start...

With regards, Matt.

 

@ANYWEATHER

Ive quoted Matt Hugo as he puts my thoughts spoken about 3 weeks ago in a much more eloquent way being dyslexic but it’s the lag impacts of the drivers spoken about by Matt. 

The 15th was just a guess based on my own knowledge on timings of lag. Nothing ground breaking or impressive just time spent studying gdsm products and making a call for this date 3 weeks ago that we’d see the charts chuck out a deep cold spell from this date onwards

[AO-]

168 looks like GFS is going for a full hit by the 15th. A lot going on with the right setup at this timeframe.

[NorthYorksWeather]

GFS 6z 180hrs 

 

[That ECM]

The culprit to volatility.

[IDO]

The modelling of the Pacific high has added uncertainty. 24-36 hours ago we were getting a strong ridge with potential for a cross-flow, but now it has gone flat. Negative with regard to destruction of the tPV but positive is that the Pac/Arctic high should feed the GH:

D1-7 GFS 06z: 

Edited January 6 by IDO