Model Output Discussion - Into the new year

[Methuselah]

As great and holy the 12Z run is, one thing still irks me: the persistence of WAA up into Eastern Europe:

    

It definitely takes some of the sting out that ESE breeze, it also limits convection by a considerable degree, IMO? But fear not -- it might be gone by the time the 18Z comes out!

Edited December 27, 2020 by Blessed Weather
Unwanted quote box removed.

[snowking]

1 minute ago, Met4Cast said:

Yes.. the current blocky pattern is trop led rather than Strat led. In theory an SSW could disrupt the pattern and shift it putting the UK on the milder side of the block.. on the other hand it could allow the pattern to double down and extend favourable blocking. We're a long way away from knowing what impact an SSW is going to have.

 

Indeed, the effects as of yet are unknown and any downwelling pattern and its imprint on the troposphere will remain unknown for a few weeks yet (that is of course assuming we get a full downwelling).

However in principle we’re starting from a base state of very low westerly momentum - so theoretically with just a further removal of westerly momentum through the various layers of the atmosphere we should just expect increasingly more amplified and static patterns setting up overall.

The very early idea from recent runs is that the majority of whatever remains of the vortex will be pushed towards the Siberian side of the hemisphere, which would suggest a continuation of HLB close to the Atlantic sector in some form, with the only real impact of a downwelling (assuming the majority Siberian sector vortex) to be more of a push of colder air available to tap into to our east, and more of a retrogression of the pattern close to the UK perhaps sending any HLB close to our North-East more towards our North-West. We may of course briefly see some goings-on in the Atlantic whilst any downwelling does take place temporarily before we revert to the more amplified state should any downwelling be poorly timed with continued amplification via EAMT in the troposphere. (And indeed it should be noted that recent ECM op runs in the strat, which split the upper vortex at least, the vortex segment left close to the US goes on to be nuked by a further warming wave which will only serve to restrict its influence - if any - further).

That’s my very first stab in the dark, but should be heavily caveated by saying this is me throwing my hat onto this peg far sooner than I really should and is only based on the output as it currently stands, so apologies if this ends up being wide of the mark.

[Man With Beard]

Just seen the UKMO and EURO4 have finally come in line with other models in getting the low to the south coast by Monday lunchtime. Really quite bothered it took them until T24 to smell the coffee! EURO4 used to be my short-term model of choice but it seems something's not quite right with it these days?

[Mike Poole]

27 minutes ago, Northern Sky said:

Is there a possibility the strat warming could have the opposite effect and have a detrimental impact on our chances for cold.

Sorry to put a fly in the ointment but hasn't that happened before?

My view, and happy to be corrected, is that the whole period build up to and after effects of a SSW should be treated as one longer evolution rather than a SSW as a thing that comes out of nowhere.  The warming itself is spectacular happening in such a short space of time, but it is part and parcel of that longer evolution, and that is why many people have been able to forecast it - I recall the 2018 SSW, we watched it all the way up and all the way down and got the rewards in the BFTE in March.  2 months model watching that was - and it delivered.

In the past, I believe some SSW events have had the UK cold before the event, rather than after.  This could be one.  But from the previous SSW events I have watched on the models, if the most likely outcome seems a split like the GFS // has been consistently showing, then this looks favourable could, while, for sure shuffling the deck, leave us double rather than quits.  But I think there is an awful lot of uncertainty about this still, so my advice would be to enjoy the increased likelihood of cold and snow before the SSW, and hope for the double down scenario as it works its way down to the trop, likely a couple of weeks after.  

Edited December 27, 2020 by Mike Poole

[That ECM]

6 minutes ago, General Cluster said:

As great and holy the 12Z run is, one thing still irks me: the persistence of WAA up into Eastern Europe:

    

It definitely takes some of the sting out that ESE breeze, it also limits convection by a considerable degree, IMO? But fear not -- it might be gone by the time the 18Z comes out!

It’ll be the clear editor button look

[Met4Cast]

10 minutes ago, Scott Ingham said:

Whats your views on stage 4. The tropospheric placement after the ssw? 

This is a weak area for me 

It's a boring answer but.. it's too early to say. We probably wont have much of an idea until the event happens which seems likely to be pegged for the 10th/11th January, though even without the SSW we're looking at an extraordinarily weak u-wind. Given the trop is already blocked with very little westerly momentum I'd expect any downwelling from the strat into the trop to be fairly quick (perhaps within a few days if all goes well) so it shouldn't take too long for models to begin factoring that in. 

I'd expect some pretty major model swings as we go into January though, I think we might already be seeing a sign of that within the GFS these last 2 days..

[Scott Ingham]

5 minutes ago, snowking said:

Indeed, the effects as of yet are unknown and any downwelling pattern and its imprint on the troposphere will remain unknown for a few weeks yet (that is of course assuming we get a full downwelling).

However in principle we’re starting from a base state of very low westerly momentum - so theoretically with just a further removal of westerly momentum through the various layers of the atmosphere we should just expect increasingly more amplified and static patterns setting up overall.

The very early idea from recent runs is that the majority of whatever remains of the vortex will be pushed towards the Siberian side of the hemisphere, which would suggest a continuation of HLB close to the Atlantic sector in some form, with the only real impact of a downwelling (assuming the majority Siberian sector vortex) to be more of a push of colder air available to tap into to our east, and more of a retrogression of the pattern close to the UK perhaps sending any HLB close to our North-East more towards our North-West. We may of course briefly see some goings-on in the Atlantic whilst any downwelling does take place temporarily before we revert to the more amplified state should any downwelling be poorly timed with continued amplification via EAMT in the troposphere. (And indeed it should be noted that recent ECM op runs in the strat, which split the upper vortex at least, the vortex segment left close to the US goes on to be nuked by a further warming wave which will only serve to restrict its influence - if any - further).

That’s my very first stab in the dark, but should be heavily caveated by saying this is me throwing my hat onto this peg far sooner than I really should and is only based on the output as it currently stands, so apologies if this ends up being wide of the mark.

If you are right about the strat (and i agree its just not my strongest area so needed some confirmation from an expert)

What January CET???

1? 1.5?

[Man With Beard]

28 minutes ago, Kasim Awan said:

Yes, shades of t w e n t y t e n 

I know we're being asked not to raise expectations, but the honest truth is, we are in the game for a memorable winter period in the weeks ahead. Sometimes the potential reaches fruition, sometimes not, and usually we don't find out until very close to T0. But the potential is there for a big freeze, undeniable.

[I remember Atlantic 252]

more like it from GFS! does go wrong again later but much later than 06Z

[Kasim Awan]

Just now, Man With Beard said:

I know we're being asked not to raise expectations, but the honest truth is, we are in the game for a memorable winter period in the weeks ahead. Sometimes the potential reaches fruition, sometimes not, and usually we don't find out until very close to T0. But the potential is there for a big freeze, undeniable.

All the hallmarks are there matey. Now we have to wait it out! Plus, some snow nowcasting in the next day or so. Brilliant phase!

[Catacol]

Time to muse. An extremely good gfs run if cold is your thing. Don’t be surprised if ECM later is less good - there will be swings and roundabouts to negotiate yet, but as has been clear for a while we are generally on an upgrade gradient at the moment. So unusual - we are used to the opposite.

Back to musing. Drivers are aligned - results are flowing. And yet in other seasons we have had drivers come into alignment and no cigar...or at least not a very good cigar. I wonder what creates these seasonal directions. In 2019 there were signs of a major SSW but things just wouldn’t click even when long range forecasts kept suggesting they would. There was something in the pattern that was resistant, and westerlies wouldn’t relax their grip. This season we have had the almost complete collapse of the Atlantic, wave break eddys happening like clockwork, bottom up impacts on the stratosphere happening with apparent ease. No issues in the last fortnight and all running counter to the seasonal forecasts.

Whatever the reason, and there will be time for post-match analysis afterwards....we are in a very good place right now. If we get that “double down” effect that @Met4Cast mentioned earlier we could be in a cold place for most of winter because a major SSW in early to mid Jan would be tough for the vortex to recover from particularly if it splits. We just need to watch for any dislocated vortex energy landing in the Atlantic. We definitely don’t want that.

Musing over. Best finish with a chart to  prevent me being subbed off. This 240h EPS mean is one of the best I have seen. Let the SSW take out the heights over SE Europe by mid month and we all better make sure we’ve found our hat and gloves.

[Thunder Snow]

When will the ssw come into play

[Scott Ingham]

4 minutes ago, Met4Cast said:

It's a boring answer but.. it's too early to say. We probably wont have much of an idea until the event happens which seems likely to be pegged for the 10th/11th January, though even without the SSW we're looking at an extraordinarily weak u-wind. Given the trop is already blocked with very little westerly momentum I'd expect any downwelling from the strat into the trop to be fairly quick (perhaps within a few days if all goes well) so it shouldn't take too long for models to begin factoring that in. 

I'd expect some pretty major model swings as we go into January though, I think we might already be seeing a sign of that within the GFS these last 2 days..

Sensible answer. I look at the heat anomalies at 10hp and factor that into High and low height placements but i dont believe its that simple is it.

If we do get a double down on current synoptics its a bit mad and fascinating to believe where we could be.

Further iniection of cold onto an already very cold and snowy surface by then....

So fascinating to watch this unfold.. as a scientist this is so much fun! 

Lets hope it enforces a lockdown as another positive in regards to covid eh!

That observation of the jumps in output.

I think your bang on its seen time and again when were about to hit rare set ups

[chris55]

Some remarkable Synoptics being modelled at the moment! Wonderful model watching! 

Although the 850s look slightly underwhelming, the surface cold with the slack flow will no doubt result in some very cold conditions building day by day. With some harsh frost lasting all day and repeating. Then we have numerous features  that could well produce snowfall....and that’s just in the next week....

The long wave pattern of the last few weeks has seen mainland Europe being engulfed by a very mild southerly feed (due to the Russian high) though this has helped to force our current low south and begin the journey to cold, its has left us without a huge cold pool to tap into. Hopefully, and as many have said, if the pattern remains, then eventually we will pull in a true Artic feed, and then all the pretty blue 850s will come flooding in to what is already going to be a very cold surface. 
 

We haven’t seen the sea freeze since 2010, I don’t thin? but it could well happen in the next 3 weeks! 

 

[Met4Cast]

2 minutes ago, Scott Ingham said:

If we do get a double down on current synoptics its a bit mad and fascinating to believe where we could be.

IF all goes well and luck is on our side.. Think 2018 BFTE but instead of being at the tail end of winter, it'd be slap bang in the middle of winter when the poles are almost at their coldest.. 

[Updated_Weather]

2 minutes ago, Met4Cast said:

IF all goes well and luck is on our side.. Think 2018 BFTE but instead of being at the tail end of winter, it'd be slap bang in the middle of winter when the poles are almost at their coldest.. 

Probably shouldn’t of said that.. people will be buzzing of that

[Catacol]

2 minutes ago, Thunder Snow said:

When will the ssw come into play

Everyone will be playing coy when considering this question....but a few pointers. Amy Butler a while back plumped for 9th Jan. Chio earlier today has said 10th. My first guess a while back of 23rd Jan looks way out. A warming is definitely going to happen - what is less clear is whether it will displace the vortex or split it in half..,.and associated with that whether we get a reversal of the flow.

Im always glass half full.....so let’s paint the best picture possible. Reversal kicks in 7th January (some runs have this so I’ll take this date as the starting point) and the vortex splits. As @snowking mentioned just now we get a vortex shard drop into Siberia and then rotate clockwise with the reversed flow. Greenland block strengthens and ridges across to Scandy because of the gap left by the split vortex. Siberian air undercuts. With such a blocked pattern already in situ thanks to favourable trop led forecasts and processes at the moment maybe downwell impacts within 7-10 days. This would mean a cold, maybe brutally cold, easterly pattern from mid Jan onwards. Duration uncertain. 

[Mike Poole]

3 minutes ago, Met4Cast said:

IF all goes well and luck is on our side.. Think 2018 BFTE but instead of being at the tail end of winter, it'd be slap bang in the middle of winter when the poles are almost at their coldest.. 

One of the poles anyway

[Scott Ingham]

10 minutes ago, Catacol said:

Time to muse. An extremely good gfs run if cold is your thing. Don’t be surprised if ECM later is less good - there will be swings and roundabouts to negotiate yet, but as has been clear for a while we are generally on an upgrade gradient at the moment. So unusual - we are used to the opposite.

Back to musing. Drivers are aligned - results are flowing. And yet in other seasons we have had drivers come into alignment and no cigar...or at least not a very good cigar. I wonder what creates these seasonal directions. In 2019 there were signs of a major SSW but things just wouldn’t click even when long range forecasts kept suggesting they would. There was something in the pattern that was resistant, and westerlies wouldn’t relax their grip. This season we have had the almost complete collapse of the Atlantic, wave break eddys happening like clockwork, bottom up impacts on the stratosphere happening with apparent ease. No issues in the last fortnight and all running counter to the seasonal forecasts.

Whatever the reason, and there will be time for post-match analysis afterwards....we are in a very good place right now. If we get that “double down” effect that @Met4Cast mentioned earlier we could be in a cold place for most of winter because a major SSW in early to mid Jan would be tough for the vortex to recover from particularly if it splits. We just need to watch for any dislocated vortex energy landing in the Atlantic. We definitely don’t want that.

Musing over. Best finish with a chart to  prevent me being subbed off. This 240h EPS mean is one of the best I have seen. Let the SSW take out the heights over SE Europe by mid month and we all better make sure we’ve found our hat and gloves.

I just love your posts mate! Best poster on the site in my honest opinion currently!

[Youcan'tbecirrus]

14 minutes ago, Man With Beard said:

I know we're being asked not to raise expectations, but the honest truth is, we are in the game for a memorable winter period in the weeks ahead. Sometimes the potential reaches fruition, sometimes not, and usually we don't find out until very close to T0. But the potential is there for a big freeze, undeniable.

It's a good point. Based on absolutely nothing more than years of failed potential in here, I will reserve any excitement until T72. If the models are still showing these synoptics at that stage then I'll be more on board. Upcoming Countryfile should be worth a look.  The '87 event began on 12th January.

[snowking]

12 minutes ago, Scott Ingham said:

If you are right about the strat (and i agree its just not my strongest area so needed some confirmation from an expert)

What January CET???

1? 1.5?

I’m not sure I’m quite that brave!

If we make the huge assumptions that:

1. The SSW eventually leads to a split

2. Within this split, the stronger vortex segment is the Siberian one

3. This pattern downwells into the troposphere

4. There is no constructive (or in our case, probably more destructive) interference from tropospheric amplification

5. The stronger vortex segment forces some colder air southward to our North/East

Then could we say sub 2c CET - I would say so.

But that is of course a lot of assumptions, rather than any sort of credible forecast

[V for Very Cold]

Sounds like the start of a mad NW competition.... what would you like see frozen over the next 31days? 
 

But seriously, amazing charts and we may be standing on the brink of a few historic weeks, and no... don’t mean Brexit!

[Tim Bland]

Could be something for eastern areas ...

[Mike Poole]

ECM T120, compared to GFS:

Looks similar maybe even faster chance of scandi link up to me, let’s see how it goes!  Remember UKMO also had this link up at T144.

Edited December 27, 2020 by Mike Poole

[Djdazzle]

The Thames freezing over? I think some have had too much of the Christmas spirit . . .