Model output discussion - The run up to Christmas

[Scott Ingham]

17 minutes ago, Catacol said:

Yeah Lorenzo - something special in the wings. Whether we get a cut off Greenland ridge or not, the global pattern is setting up for a proper split SSW. Given the likely pattern at the New Year I’m tempted to suggest we will be unlucky if we don’t see some icy fallout here.....though trop impacts of a SSW are a lottery really. Only time will tell but these are the best midwinter synoptic preconditions since 2010.

Im genuinely excited mate about the next two months. I think its time to bin the seasonal if we get what we think is very possible 

[Updated_Weather]

Let’s make the most of the next 3 “mild” days.. might be a while before we use that term

[Mike Poole]

3 minutes ago, Scott Ingham said:

We called the GFS mate. Its come together. How beautiful is that warming?!

Hey, it is still at T384!  

It is looking good and as predicted, and the other models are coming in line in the trop, but this SSW split has to be very nicely aligned or it will be nothing, not double.  Fascinating to watch it unfold, but nothing is guaranteed.

[markw2680]

As things stand Christmas to new year could be pretty special for many, after that who knows as it’s just to far away, next hurdle is to maintain these kind of charts through the night and into tomorrow, normally you wake up to downgrades but this time it all just seems a lot more solid. I seem to remember the last time things seemed this consistent was 2013 and 2010 and we all know what happened there. 

[Scott Ingham]

4 minutes ago, Mike Poole said:

Hey, it is still at T384!  

It is looking good and as predicted, and the other models are coming in line in the trop, but this SSW split has to be very nicely aligned or it will be nothing, not double.  Fascinating to watch it unfold, but nothing is guaranteed.

Oh sorry mate i meant the initial Greenland high. The strat is a lot more reliable forecast wise but you are right positionally it could all change 

[Uncertainty]

14 minutes ago, Scott Ingham said:

We called the GFS mate. Its come together. How beautiful is that warming?!

Beautiful indeed! It’s such a contrast from last years well oiled machine.

This +EAMT is quite something, here at day 11! 

How stunning to have a gigantic Siberian high AND a huge -NAO concurrently. 

[kold weather]

Well not sure what else needs to be said that hasn';t been said.

So from a position of wanting maximum cold, I'd like to see the LP that comes SE to b more sharply aligned N-S, at the moment irs a little too bowling ball from the models which allows somewhat milder air to entrain into the circulation. A sharper N-S alignement limits that and is probably 2-4c colder aloft.

However as I said this morning, that set-up is still IMO cold enough for snow. I'd like it a little colder just to remove some more marginality however with the right evolution of the LP somewhere probably stands  good shot at getting a snow event on the 27-29th.

Beyond that and things get increasingly tasty, models are keen to keep on attempting to ridge towards Greenland and LPs keep diving S/SE. Of course much like the spell coming up, much depends on exact orientations and angle of attacks as to how cold it really gets, but the chance is there for a sustained cold spell.

And thats before the warming really kicks up a gear and the PV basically falls apart. All options from that point onwards are on the table. I agree with others, we'll be unlucky from here not to get one sustained cold spell from this with big snow chances given the tendency for upper trough to be near our shores so far this winter.

[snowbob]

I can’t believe what I’m reading 

but experience won’t let me go yet 

still too many fingers burnt 

maybe il wait till the mornings run.

surely they won’t be the same.

will they ??

[Connor Bailey Degnan]

Overall, the best output since that of February 2018. Granted, it's no where the near the nirvana produced then and people should accept that. The risk of wintry precipitation, whether it be sleet or snow, is on the rise, especially post Christmas. A small chance of something wintry affecting Eastern coasts - Christmas eve into Christmas day which needs watching! After such a dreadful year, I, and the majority in here will be happy with the overall output going forward. Merry Christmas all

[Cheshire Freeze]

6 minutes ago, Uncertainy said:

Beautiful indeed! It’s such a contrast from last years well oiled machine.

This +EAMT is quite something, here at day 11! 

How stunning to have a gigantic Siberian high AND a huge -NAO concurrently. 

That actually looks VERY similar to the CFS mean z700 plots from back in September/ October. 

I'll see if I can dig out the old post of mine where I noted there was a stark SSW signature.

[Scott Ingham]

1 minute ago, Uncertainy said:

Beautiful indeed! It’s such a contrast from last years well oiled machine.

This +EAMT is quite something, here at day 11! 

How stunning to have a gigantic Siberian high AND a huge -NAO concurrently. 

Oh wow!!! This is the one forecast for first week in January! 

I dont know where you stand but ive been doing some research and it seems the extreme heat in Siberia and Asia this year that caused the record breaking fires set off this domino effect of extreme high pressure over the himalayas and in my opinion a big factor in the state of glaam compared to what wed expect in a nina year. Look at 2010. Search russian heat. Was another record breaker and we know about the state of the Glaam that year that drove the cold.

Its from this btw that we will

1) See another burst in amplification extending the meridonial pattern and I believe a griceland high to follow our Greenland one and

2) Be the final wave that causes the ssw.

 

So in future im keeping an eye on Russian summer heat as a precurser for winter 

[Kasim Awan]

4 minutes ago, Connor Bailey Degnan said:

Overall, the best output since that of February 2018. Granted, it's no where the near the nirvana produced then and people should accept that. The risk of wintry precipitation, whether it be sleet or snow, is on the rise, especially post Christmas. A small chance of something wintry affecting Eastern coasts - Christmas eve into Christmas day which needs watching! After such a dreadful year, I, and the majority in here will be happy with the overall output going forward. Merry Christmas all

Good summary. Amazing consistency now, 9/10 times this consistency is had the cold follows in. Something significant afoot.

[Cheshire Freeze]

12 minutes ago, CreweCold said:

That actually looks VERY similar to the CFS mean z700 plots from back in September/ October. 

I'll see if I can dig out the old post of mine where I noted there was a stark SSW signature.

Couldn't find the post I was looking for but I remember saying the CFS looked very 'SSW' and someone telling me it was nonsense as the model could not pick up a SSW that far out!

Anyway, found this from September-

[Kasim Awan]

1 minute ago, CreweCold said:

Couldn't find the post I was looking for but I remember saying the CFS looked very 'SSW' and someone telling me it was nonsense as the model could not pick up a SSW that far out!

Anyway, found this from September-

It obviously can't be determined whether the model was forecasting a SSW from that. I don't think long range output forecasts SSWs as such - more just a general stratosopheric disruption. I believe there are certain surface conditions more conducive for SSW surface waving. This may have lead the model down this disrupted PV path. We have some of these requisites now.

Also note Jan 13 seems a good match for the SSW and split forecast. Interesting.

I'm not a huge fan of the strat, so this will probably be my only contribution.

[Uncertainty]

23 minutes ago, CreweCold said:

That actually looks VERY similar to the CFS mean z700 plots from back in September/ October. 

I'll see if I can dig out the old post of mine where I noted there was a stark SSW signature.

Glosea didn’t get the memo! Outstanding seasonal model... please be wrong this time! I‘d be so chuffed if the great minds on this forum can outthink the supercomps. The signs have been there since August at least. You said it yourself CC many times. tbf to the CFS many individual runs have gone with it but the mean can’t help but revert to climo.

@Scott Ingham that’s beyond my paygrade but the persistent heights in that region are doubtless the big NH story this year. I’m sure there’s a link back to that crazy warm period they had In the summer (they even had a level 3 estofex for supercells near southern Siberia at one point) and our current stratospheric  position. Their persistence through November was surely the critical factor. Siberia is now truly bitter - as Japan has recently discovered!!!

 

Edited December 21, 2020 by Uncertainy

[ITSY]

Not bad! Better than 12z in fact

[Cheshire Freeze]

4 minutes ago, Kasim Awan said:

It obviously can't be determined whether the model was forecasting a SSW from that. I don't think long range output forecasts SSWs as such - more just a general stratosopheric disruption. I believe there are certain surface conditions more conducive for SSW surface waving. This may have lead the model down this disrupted PV path. We have some of these requisites now.

Also note Jan 13 seems a good match for the SSW and split forecast. Interesting.

I'm not a huge fan of the strat, so this will probably be my only contribution.

It wasn't the chart I was looking for- the one I posted at the time had more striking anomalies and the polar regions were dark orange. It was definitely signifying a SSW

[BlueHedgehog074]

2 hours ago, Team Jo said:

Come on lads. Take the personal sniping elsewhere yeah? 

There’s something else too: We’ll send your name off to Santa who’ll put you down on the naughty list. Nobody wants that to happen now do they? So do make sure you’re good

[Scott Ingham]

42 minutes ago, Uncertainy said:

Glosea didn’t get the memo! Outstanding seasonal model... please be wrong this time! I‘d be so chuffed if the great minds on this forum can outthink the supercomps. The signs have been there since August at least. You said it yourself CC many times. tbf to the CFS many individual runs have gone with it but the mean can’t help but revert to climo.

@Scott Ingham that’s beyond my paygrade but the persistent heights in that region are doubtless the big NH story this year. I’m sure there’s a link back to that crazy warm period they had In the summer (they even had a level 3 estofex for supercells near southern Siberia at one point) and our current stratospheric  position. Their persistence through November was surely the critical factor. Siberia is now truly bitter - as Japan has recently discovered!!!

 

Im in the process of doing research with a view to putting a paper together on it.

I spent an evening musing at this years tropical patterns and it took me to 2010 and i looked at similarities right through the year and found two things. 

Intense summer siberian heat and record breaking wild fires and low arctic sea ice on the Russian side (which obviously go hand on hand) 

It could he more sea surcace temperatures even in the Russian arctic. All that latent heat and energy i believe along with heat from the continent affecting higher pressures in the same areas in the winter increasing prevalence on himalayn high pressures capable of driving torque events. Im only scratching the surface but just thought id throw the idea out to see if anyoje can add any ideas

[Stu_London]

38 minutes ago, ITSY said:

Not bad! Better than 12z in fact

As I thought, not quite as tight toward the end of the run - but the majority still stay cold and its too far away to worry about anyway. The critical period 27-29Dec, the op is still a little higher than the mean - so there is still an angle to achieve some short term upgrades which would reduce the marginality worry for those areas. Different synoptically, but reminds me a bit of December 1990. Most areas midlands northwards got a pasting, but some areas close to sea level saw little settling snow. 

I lived in Darlington at the time and was most frustrated to hear on the radio that all main routes into the town were impassable due to drifting snow, yet it was a wet slush fest outside. Soon forgotten however, as February 1991 made up for it BIGTIME 

[Scott Ingham]

59 minutes ago, CreweCold said:

Couldn't find the post I was looking for but I remember saying the CFS looked very 'SSW' and someone telling me it was nonsense as the model could not pick up a SSW that far out!

Anyway, found this from September-

That high pressure over the Ural region has been very persistent and has been our friend. Very important piece of the jigsaw. I remember when i wanted that to persist n others were saying it was wasting time on winter you and catacol were on the same lines knowing we needed it for a ssw

[Cheshire Freeze]

1 minute ago, Scott Ingham said:

That high pressure over the Ural region has been very persistent and has been our friend. Very important piece of the jigsaw. I remember when i wanted that to persist n others were saying it was wasting time on winter you and catacol were on the same lines knowing we needed it for a ssw

Yep it was critical for the bigger picture going forward

[Stu_London]

3 minutes ago, Scott Ingham said:

Im in the process of doing research with a view to putting a paper together on it.

I spent an evening musing at this years tropical patterns and it took me to 2010 and i looked at similarities right through the year and found two things. 

Intense summer siberian heat and record breaking wild fires and low arctic sea ice on the Russian side (which obviously go hand on hand) 

It could he more sea surcace temperatures even in the Russian arctic. All that latent heat and energy i believe along with heat from the continent affecting higher pressures in the same areas in the winter increasing prevalence on himalayn high pressures capable of driving torque events. Im only scratching the surface but just thought id throw the idea out to see if anyoje can add any ideas

I noticed a few similar models scenarios cropping up in October and November that had shades of 2010 - however, 2010 was a one in 50 year event, even disregarding background warming. 

I'd be happy if 1990/91 proved a good analogue match - I don't know if there was a SSW in Jan 1991, so i might be talking rubbish.

[Scott Ingham]

5 minutes ago, CreweCold said:

Yep it was critical for the bigger picture going forward

It was indeed mate yeah but people wanted the front loaded winter and couldnt see the larger picture. Theyll be happy if the ssw comes off that its stayed stubborn. Its not just been the ssw. Its kept AAM above neutral contrary to what would be expected in a moderate la nina year. Its been critical both short medium and long term

[Allseasons-Si]

That is a good set of gefs ens@-5.