Model Output Discussion - the cold has arrived

[geordiekev]

5 minutes ago, Eagle Eye said:

Signs on the ECM extended that we may be moving towards a repeating pattern with a fairly mobile MJO trying it's best to keep moving towards phases 5-8 and hence the increases 6 and/or 7 chance as well. So a potential repeating pattern on the cards as we go into the early/mid January period after a short zonal dip. For now, Im going to leave that alone though and let it be FI but let's hope it becomes a repeating trend. If it does then this Winter COULD end up being like 'the old Winters' but I'm not going to ramp yet, instead, all I'm going to say is that it doesn't guarantee a -VE NAO, just increases the chances and its still too far out that we can't be sure of anything yet.

The downstream effects of the East Asian jet retraction interest me. We're into the time where we can see the clear amplification of Rossby thermal transfer cropping up on the models in a fairly reliable time although exact handling will be very off at this point. The effects on how Eddy's are handled may be negative but the generalised conception of increasing Eddy Heat Flux especially in the upper Troposphere may be slightly better handled than usual. Usually , this would probably increase the -VE AO but we're in such a -VE AO dip that it may just delay the recovery of the AO through the formation of that UK and/or Scandinavian blocking signal that's starting to persist on the models. It's still too far out to worry about localised dynamics of the high but the signal is showing for the blocking to form and of course how it forms will affect the short term gain at that time but as long as the wandered blocking pattern keeps up the relative pattern flip cold throat should exist. I think up until very late December potentially later than that, this pattern may be able to keep itself going synoptically hence the cold chance probably persists till around early January. Then we've got the potential MJO influence and that may happily coincide with another energy scattering PNA cycle.

Me thinks the scattering of energy interacting with the more southerly based jet will drift up hot air from North Africa which may cause some areas of Europe to see ridiculously mild air for this time of year and probably not something you associate so close to a quite significant -VE AO pattern. Just using 1 model run to show what I mean is probably not a good idea at the time range that I'm talking about and it goes against my principals but I'm just using it to show the mild air that could possibly be drawn up.

It's very unlikely to look anything like that but it does show what could be drawn up by the energy and amplification scattering interacting with the high just off the coast of North Africa. A very interesting thing as we go closer to time I think but we still can't be sure that the North African (ish) High will be interacted with nor the direction that its drawn up so we could end up seeing one extreme or the other.

Looking more into the short term future...

Initial pulses of colder air in a cold pattern and maybe the formation of a shortwave or something similar that could still end up dumping a decent amount of snow somewhere, then...

Cold air that would normally look blocked in fairly well seems to get thwarted to the south and a pulse of amplification correlated with the  downstream effects of the PNA pattern (correlated with the East Asian jet retraction fairly well, funny how everything links together) but how long it stays for is hard to tell for now. There is a chance it could just be a mild blip and that it goes on to prop up the -VE AO pattern as discussed earlier. Or it could hold itself in for longer and set itself in for a longer time, for now I just don't know and its fairly evenly balanced.

Yes, anyone who hasn't seen the Dec 62/63 pattern defo worth looking at the pattern evolution in our part of the Globe. Has very similar repeating scenarios interlaced with lows sliding through providing the moisture.

BTW I'm not touting 62/63 18ft drifts as know some have aversions to using historic Winters as comparison 

[sukayuonsensnow]

10 minutes ago, Tim Bland said:

55cm south wales and 45cm central areas by day 10…please father Christmas this is all I want for Christmas ! 

Would be nice! Of course by then the models would do the thing of adjusting the low pressure more south so places south of the M4 would get the storm. (Or it just ends up in France)

Next weekend and beyond is still FI but will be watching with interest. One thing I have noticed more if the GFS trying to bring milder air from the northwest or west rather than southwest next weekend, which would be less ideal especially for transient snow/cold reload potential.

[Allseasons-Si]

4 minutes ago, nick sussex said:

The ECM just avoids a phasing calamity as the upstream troughing edges east and gives those remaining heights a nudge east .

Just enough trough disruption sets up that frontal snow for parts of the UK .

Its really edge of the seat stuff though. It does highlight though how important it is to close off the high otherwise what remains off those heights get drawn too far nw at the crucial timeframe .

The jma does it in style Nick as @Mike Poole commented on but i wanted to post the animation of it,...great chart this

 

[damianslaw]

15 minutes ago, Eagle Eye said:

Signs on the ECM extended that we may be moving towards a repeating pattern with a fairly mobile MJO trying it's best to keep moving towards phases 5-8 and hence the increases 6 and/or 7 chance as well. So a potential repeating pattern on the cards as we go into the early/mid January period after a short zonal dip. For now, Im going to leave that alone though and let it be FI but let's hope it becomes a repeating trend. If it does then this Winter COULD end up being like 'the old Winters' but I'm not going to ramp yet, instead, all I'm going to say is that it doesn't guarantee a -VE NAO, just increases the chances and its still too far out that we can't be sure of anything yet.

The downstream effects of the East Asian jet retraction interest me. We're into the time where we can see the clear amplification of Rossby thermal transfer cropping up on the models in a fairly reliable time although exact handling will be very off at this point. The effects on how Eddy's are handled may be negative but the generalised conception of increasing Eddy Heat Flux especially in the upper Troposphere may be slightly better handled than usual. Usually , this would probably increase the -VE AO but we're in such a -VE AO dip that it may just delay the recovery of the AO through the formation of that UK and/or Scandinavian blocking signal that's starting to persist on the models. It's still too far out to worry about localised dynamics of the high but the signal is showing for the blocking to form and of course how it forms will affect the short term gain at that time but as long as the wandered blocking pattern keeps up the relative pattern flip cold throat should exist. I think up until very late December potentially later than that, this pattern may be able to keep itself going synoptically hence the cold chance probably persists till around early January. Then we've got the potential MJO influence and that may happily coincide with another energy scattering PNA cycle.

Me thinks the scattering of energy interacting with the more southerly based jet will drift up hot air from North Africa which may cause some areas of Europe to see ridiculously mild air for this time of year and probably not something you associate so close to a quite significant -VE AO pattern. Just using 1 model run to show what I mean is probably not a good idea at the time range that I'm talking about and it goes against my principals but I'm just using it to show the mild air that could possibly be drawn up.

It's very unlikely to look anything like that but it does show what could be drawn up by the energy and amplification scattering interacting with the high just off the coast of North Africa. A very interesting thing as we go closer to time I think but we still can't be sure that the North African (ish) High will be interacted with nor the direction that its drawn up so we could end up seeing one extreme or the other.

Looking more into the short term future...

Initial pulses of colder air in a cold pattern and maybe the formation of a shortwave or something similar that could still end up dumping a decent amount of snow somewhere, then...

Cold air that would normally look blocked in fairly well seems to get thwarted to the south and a pulse of amplification correlated with the  downstream effects of the PNA pattern (correlated with the East Asian jet retraction fairly well, funny how everything links together) but how long it stays for is hard to tell for now. There is a chance it could just be a mild blip and that it goes on to prop up the -VE AO pattern as discussed earlier. Or it could hold itself in for longer and set itself in for a longer time, for now I just don't know and its fairly evenly balanced.

Another very informative post, I'll take a 2 day blip please, preferably say 20-22 Dec, then cold to return. Not too much to ask!

[geordiekev]

14 minutes ago, Allseasons-si said:

The jma does it in style Nick as @Mike Poole commented on but i wanted to post the animation of it,...great chart this

 

Interesting seeing this tripole chart pop up on quite a few different models now & was touted in the longer term models last week, so would seem to be gathering support

[stodge]

Evening all

While I'm now hopelessly smitten with JMA after tonight's run, the fact remains beyond T+120, as I said last night, nothing is resolved.

Tonight's T+144 charts from UKM, GFS OP, ECM, GEM and JMA reflect the uncertainty modelling heights to the north west, west and south west.

Clearly, those looking for the continuation of cold will not want to see heights to the south and an LP forming to the north west but at this stage it's all very unclear.

[BlueHedgehog074]

While the High Pressure is more concentrated towards Southern/South-Eastern Iceland on tonight’s 12Z ECMWF run, both 12Z runs from today and yesterday have been consistent with that Low out West slithering like a snake towards the South of the UK underneath the wedge/ridging to the North/North-West. Good boy, Low! And good job block for showing that Low who’s the boss around here.

Will help to keep the chilly weather going for many places. (For Monday 19th): 

Yesterday’s 12Z run:

Tonight’s 12Z run:

[feb1991blizzard]

41 minutes ago, nick sussex said:

The ECM just avoids a phasing calamity as the upstream troughing edges east and gives those remaining heights a nudge east .

Just enough trough disruption sets up that frontal snow for parts of the UK .

Its really edge of the seat stuff though. It does highlight though how important it is to close off the high otherwise what remains off those heights get drawn too far nw at the crucial timeframe .

yes, i named this run the nick sussex run when it came out!

[goosey007]

1 hour ago, Tim Bland said:

Expect most would be happy with that! 40cm for some !!

January 1984 style for south wales if this came off ….. of course JFF corrections of 100s miles likely at this range…..but it’s in line with the mets update …..something to keep an eye on on but if I’m honest with myself it will probably be gone on the next run ….

[ANYWEATHER]

Another attempt from the models well ecm to break the cold.....Big difference between the 00z and 12z

[Blizzardof82]

JMA bank 

[MATTWOLVES 3]

Don't worry folks the referee is most definitely married to a French woman  

Are you dreaming of a Northern Hemisphere that promises blocking for Xmas? Well CFS says hell yeh.

[Blessed Weather]

40 minutes ago, Eagle Eye said:

Signs on the ECM extended that we may be moving towards a repeating pattern with a fairly mobile MJO trying it's best to keep moving towards phases 5-8 and hence the increases 6 and/or 7 chance as well. So a potential repeating pattern on the cards as we go into the early/mid January period after a short zonal dip. For now, Im going to leave that alone though and let it be FI but let's hope it becomes a repeating trend. If it does then this Winter COULD end up being like 'the old Winters' but I'm not going to ramp yet, instead, all I'm going to say is that it doesn't guarantee a -VE NAO, just increases the chances and its still too far out that we can't be sure of anything yet.

(SNIPPED)

Really enjoy your informative and upbeat posts EE.  
Unfortunately - and assuming current forecasts are correct - I'm not optimistic about the MJO helping with a pattern repeat in the short-term. The GMON (GEFS extended) forecast, the BOMM (Australian Met ensemble bias corrected) forecast and the EMOM (ECMWF ensemble bias corrected) forecasts to 6th - 8th Jan has the MJO in the COD (Circle of Death). Which means the MJO is largely indiscernible from background noise and will have neglible impact on global weather patterns.

And even if the MJO emerges from the COD in early January, add the typical 10 to 12 day lag and it's likely to be well into Jan before we would see an impact in this part of the world. Current forecasts:

GMON BOMM EMOM

[Ali1977]

3 minutes ago, MATTWOLVES said:

Don't worry folks the referee is most definitely married to a French woman  

Are you dreaming of a Northern Hemisphere that promises blocking for Xmas? Well CFS says hell yeh.

That chart would do, as would a new ref!! 
I just have the feeling we are in for a huge chart flip for later this week over the next 24 hours, something like this or the JMA would do

[Vikos]

good ec eps for at least the next 7-8 days. It just can get better…

[Allseasons-Si]

ECM control siding with his big brother here at 192...

[bluearmy]

5 minutes ago, Allseasons-si said:

ECM control siding with his big brother here at 192...

It goes wrong thereafter …..

[Allseasons-Si]

1 minute ago, bluearmy said:

It goes wrong thereafter …..

Yep,...it looked good up to that point but at least it was a step in the right direction not phasing that low in the Atlantic

still plenty to keep an eye on until then me thinks

 

[Jeremy Shockey]

ECM 12z ensemble mean

 

lets hope the Op is right .........this cold spell can extend beyond Christmas if we are fortunate

[seaside boy]

2 hours ago, geordiekev said:

Yes, anyone who hasn't seen the Dec 62/63 pattern defo worth looking at the pattern evolution in our part of the Globe. Has very similar repeating scenarios interlaced with lows sliding through providing the moisture.

BTW I'm not touting 62/63 18ft drifts as know some have aversions to using historic Winters as comparison 

You can't do that now...the world's weather has  changed, we can only look forward, and stop looking backwoods

[MattH]

42 minutes ago, Blessed Weather said:

Really enjoy your informative and upbeat posts EE.  
Unfortunately - and assuming current forecasts are correct - I'm not optimistic about the MJO helping with a pattern repeat in the short-term. The GMON (GEFS extended) forecast, the BOMM (Australian Met ensemble bias corrected) forecast and the EMOM (ECMWF ensemble bias corrected) forecasts to 6th - 8th Jan has the MJO in the COD (Circle of Death). Which means the MJO is largely indiscernible from background noise and will have neglible impact on global weather patterns.

And even if the MJO emerges from the COD in early January, add the typical 10 to 12 day lag and it's likely to be well into Jan before we would see an impact in this part of the world. Current forecasts:

GMON BOMM EMOM

The MJO signal is being muddied by the tropical features in the I/O and W Pacific and RMM plots in particular are crap for forecasting ahead - long story short there is still a good shout of a 4-5-6-7 progression rest of Dec. 

[Eagle Eye]

36 minutes ago, Blessed Weather said:

Really enjoy your informative and upbeat posts EE.  
Unfortunately - and assuming current forecasts are correct - I'm not optimistic about the MJO helping with a pattern repeat in the short-term. The GMON (GEFS extended) forecast, the BOMM (Australian Met ensemble bias corrected) forecast and the EMOM (ECMWF ensemble bias corrected) forecasts to 6th - 8th Jan has the MJO in the COD (Circle of Death). Which means the MJO is largely indiscernible from background noise and will have neglible impact on global weather patterns.

And even if the MJO emerges from the COD in early January, add the typical 10 to 12 day lag and it's likely to be well into Jan before we would see an impact in this part of the world. Current forecasts:

GMON BOMM EMOM

I do agree with you but was trying to see the positive side of things (especially after the England match) and these patterns could repeat (however unlikely). I think the main help though will be through the GWO which looks like it could repeat a +VE frictional or mountain torque phase and we see another wave train scattering energy downstream. Of course this is in FI for now but I wouldn't be surprised if we saw it, just may be a bit more delayed than my initial post states.

[sheikhy]

3 minutes ago, Jeremy Shockey said:

ECM 12z ensemble mean

 

lets hope the Op is right .........this cold spell can extend beyond Christmas if we are fortunate

Not too confident now!!!thats a massive outlier!!!!!the op is surely gona be wronng!!

[Froze were the Days]

ECM 0z's (milder by next weekend) v 12z's (cold remaining with possible slider)...of the last 2 days, which one will win out? Overall NH profile looks a lot different and favourable to recent years maybe bar 20/21.

[LRD]

12 minutes ago, Jeremy Shockey said:

ECM 12z ensemble mean

 

lets hope the Op is right .........this cold spell can extend beyond Christmas if we are fortunate

Oh dear, that's a shocker

Or a trend setter. I can probably guess which

2 questions this evening - will I ever see an Englishman lift the football World Cup in my lifetime and will I ever see snow in the air and/or on the ground at Xmas ever again?

Edited December 10, 2022 by LRD