Model Output Discussion - Colder spell ending, what's to follow?

[Mike Poole]

1 minute ago, Frosty Winter said:

ECM monthlies remain positive for the second half of December despite the less positive shorter-term output.

Hang on Matt just said they were not good, are we talking about the same run?

[Matt H]

2 minutes ago, Mike Poole said:

Hang on Matt just said they were not good, are we talking about the same run?

 

[Uncertainty]

Whilst I understand the frustration of many forum members tonight, especially after the promise of yesterday evenings GFS suite, it must be stressed that the end of December is not certain to be a zonal washout with a slug and straight line southwesterlies. This in itself is a bonus for the Christmas holiday. Even those far removed from the weather obsessed folk know the singularity for the Christmas period: stormy, wet, mild and miserable. Here in the valley of the Cumbrian hills I’m more likely to be nervously checking river levels than sculpting snowmen.

Whilst, at present, it seems unlikely based on the latest high res charts that we can force enough amplification to connect to those Arctic heights, there is a genuine possibility that we will be able to in the Christmas period. First, the GEFS  for Christmas  Eve, er, Eve:

Blocking over Greenland and low pressure south of the UK? Are you telling me you wouldn’t take that in an average year without knowing the context? 

Next, Christmas Eve itself, this time from the GEPS mean:

Stronger heights over Greenland and a trough in the channel? Yes I know many of the perturbations  would be mild but come on, you’d take that anomaly any day of the week.

Thirdly, the ECM. The day 10 mean on the 12z was a step back from the 0z with the low closer to the UK, stronger and further North too. This led me to believe the blocking in the EPS would collapse, so did it? 

No sir it didn’t. @Daniel*has kindly posted the longer term EPS and what do we have from the world’s leading medium range prediction tool? A euro low, Greenland heights and colder than average temps. I’ve been through all the members - 10 or so have a genuine GH, some have Scuero blocking, a few a UK high and others have the low over the UK. But crucially, barely any have purple over Iceland, red over Europe and diagonal lines over the UK. The ‘usual fayre’ conspicuous by its absence.

As for the 46? It’s rubbish from week 4 onwards yes, but wouldn’t you not rather it was good in weeks two and three, which might actually happen?

Week 2:
 

How is that not good? A strong high anomaly over Griceland and a southerly tracking jet. Gorgeous.

Week 3:

Residual heights to the North and the jet into Iberia. Yes please.

What about the MJO, this is where it gets complicated. Some evidence that the Westerly qbo is finally descending  to the higher end of the troposphere, which could scupper the progression of the wave into phases 7, 8 and 1. 
 

You can see the gold coloured WQBO leaking into the lower levels of the atmosphere which could act as a barrier to the mjo... but in the latest day or two that seems to have backed off.

Regardless, the 46 actually progresses the MJO deep into phase 8/1

More amplitude in phase 6/7 would be nice but it’s hardly the worst place to be for favourable tropical forcing with a weakened stratosphere ripe to be knocked down now is it?

And what of the mighty stratospheric polar vortex, so often the destroyer of (cold mid latitude) worlds? 
 

A small cluster reverse but many are weak and few are strong. Again, in climatological VI, an excellent projection.

So there you have it. Narnia? Nope, Interesting? Yes. Potential? Loads.

Don’t give up on the second half of December yet...

[blizzard81]

4 minutes ago, Mike Poole said:

Hang on Matt just said they were not good, are we talking about the same run?

He was referring to Jan. 

[Mike Poole]

3 minutes ago, blizzard81 said:

He was referring to Jan. 

Too far away to be worth bothering about re ECM 46!!  We could have had an SSW, volcanic eruption, Brexit and alien invasion by then.  I really don’t know why they run it twice a week.  It has historically been almost laughably wrong at times!  Thanks for clearing that up - by January I think we will probably taking guidance from the evolution of the strat, anyway.  

[blizzard81]

14 minutes ago, Frosty Winter said:

ECM monthlies remain positive for the second half of December despite the less positive shorter-term output.

Surely you don't get much better than that for Christmas. 

[mountain shadow]

Just now, blizzard81 said:

Surely you don't get much better than that for Christmas. 

It depends. 

We live on a relatively small part of the globe. That could bring us South Westerlies as well as North Easterlies depending on the exact positions of the ridges and troughs.

[MATTWOLVES 3]

23 minutes ago, Mike Poole said:

Hang on Matt just said they were not good, are we talking about the same run?

Heights were looking better for the 2nd half the month Mike, I didn't view any further and made the assumption they would be falling away as we entered January.. I've only viewed up to the 26th of December.. I'm having  trouble multi tasking here, I'm trying to watch Benidorm at the same time..

Gr8 post @DiagonalRedLine you do a grand job, and tbh most of you guys let this run pretty freely... So all good.

@Mike PooleI said earlier the 46 looks more positive than the last few runs... Sorry if I got a little mixed up with my last post... Its all good my man... Its Christmassssssssz

Oh and awesome summary @Uncertainy

Edited December 10, 2020 by MATT☀️

[Tim Bland]

4 minutes ago, blizzard81 said:

Surely you don't get much better than that for Christmas. 

Problem is anomalies don’t always tell the full story. Here is an example of a similar anomaly that leads to average temps and rain for most....

[blizzard81]

1 minute ago, Tim Bland said:

Problem is anomalies don’t always tell the full story. Here is an example of a similar anomaly that leads to average temps and rain for most....

I get your point and also mountain shadows but I think things are looking good for Christmas week. 

[SMU]

Reviewing the GFS currently it has shelf life accuracy to about T120-132. 

After that the phasing of the upstream trough off Canada & the slow seeping of energy out of the Atlantic low looks very poorly modelled > & as ever the only solution is 'East'.

[Mike Poole]

It has just occurred to me that there hasn’t been much talk about the pub run - then I looked at Meteociel. 

[Matt H]

Me thinking the GFS 18z would be a better run tonight: 

[DanDorsetUK]

Quick question I kinda jokingly posted in the moans thread. The solar flare we had hit in the early hours of this morning but just a glancing blow and slightly weaker than expected. Could this by any chance have caused the models today to react to that event?

[damianslaw]

Reliable timeframe, a rather stuck pattern, low pressure coming unstuck - hitting a brick wall over the UK, and turning in on itself, all thanks to strong heights to our east and south, and increasingly so north, it simply has nowhere to go.. 

Longer term, just need a bit of an amplification in the pacific jet to have a knock on domino effect and allow for a ridge to develop over mid atlantic which in turn will allow for colder air to feed down behind the trough and give it a kick. Signs of this from ECM 240 hr output. GFS doing its usual and steamrolling the atlantic in.. but both do show a more southerly tracking jet in the run up to christmas, some quite cold air will be pulled into the trough from the N Atlantic, which could make for an interesting period - boundary lines between snow and rain over the UK.

I'm pleased this isn't summer, as the outlook would be very poor with days of rain.

 

[Mike Poole]

Sorry - double post, deleted!

Edited December 10, 2020 by Mike Poole

[Man With Beard]

29 minutes ago, Frosty Winter said:

ECM monthlies remain positive for the second half of December despite the less positive shorter-term output.

The ensembles for D12-D15, when studied individually, do tend to have better heights than usual to the north, but note the lack of positive anomalies directly west - there are too many ensembles with low pressure centred west or south west to get excited about a white Christmas just yet. 

[damianslaw]

15 minutes ago, blizzard81 said:

I get your point and also mountain shadows but I think things are looking good for Christmas week. 

Not saying this will happen, but shades of Dec 2000 christmas week.. 

[BlueHedgehog074]

Although just a pretty standard, chilly, North-Westerly flow over the UK from the 18Z GFS at 216 hours...

... the GFS could do with going for more drinks. Not drunk enough yet it seems. (Could be quite a lot worse though). 

Christmas Day itself still a fair number of days away to write off at the moment. 

[snowspotter]

18 minutes ago, Steve Murr said:

Reviewing the GFS currently it has shelf life accuracy to about T120-132. 

After that the phasing of the upstream trough off Canada & the slow seeping of energy out of the Atlantic low looks very poorly modelled > & as ever the only solution is 'East'.

Absolutely nailed there . If you compare the GFS at 8 days there is literally no similarity . Ridiculous really . Not a lot of point commenting after that really is there 

[Johnp]

FWIW, tonight's extended JMA (which was similar to UKMO in earlier stages) went on to become quite promising. 

[Day 10]

7 minutes ago, damianslaw said:

Not saying this will happen, but shades of Dec 2000 christmas week.. 

Just shows you, 2 weeks is a long time in weather.

10th Dec 2000

Christmas Day 2000

[SMU]

More ENS taking a different approach to the phasing of energy upstream.

[DanDorsetUK]

Obviously there is no evidence to suggest the solar flare that hit in the early hours caused the models to react today, although they can affect equipment. But I do find it quite coincidental. It's almost worth keeping an eye on such things in the future to see if any such solar flares react with the models temporarily. Obviously millions of data pass through these models maybe solar activity is one of them. Who knows.

[bluearmy]

Bit surprised that we’ve had a long run of gfs ops which haven’t reflected one of the more amplified gefs members that have a decent representation each suite in fi .....

I think the chances of something notably wintry for Xmas is receding fast and we will soon be looking beyond that period towards new year