Model Output Discussion 29th December - Into mid-Winter.

[mb018538]

Thanks as ever Tamara.

Looks like everything is lining up for a return to our status quo of zonality. Last time this was modelled earlier in the winter it only lasted a week or so, and barely affected some areas, before blocking returned. How long will it last this time??

[Guest]

My word, it's quiet on here today. l shall try to inject a little more optimism into the current mood! As I said before, I believe that the models are continuing to seriously underestimate the depth and breadth of the European cold block. During the last 24 hours, the cold has steadily intensified again and has spread back westwards to include almost all of France. The cold, which never left the extreme east and south-east of the UK over the weekend, has been slowly but steadily pushing north-westwards in the UK. It is also slowly deepening in the south-east as the European cold continues to be advected from the continent. There are just hints that run by run, the models are extending the period of this continental "drift" beyond next weekend.  

Current Surface Temperatures updated every few minutes (the time shown is 1 hour ahead of GMT):

 

Here is the link to the site: http://www.meteociel.fr/observations-meteo/temperatures.php    If you click on the "animation sur 24" at the top you can see the hourly changes during the last 24 hours (I still have not mastered the skill of pasting the live animated charts across to here). This shows the intensification of the cold and the spread westwards. You need to allow for the natural diurnal nighttime/daytime min/max temperature changes but the overriding progression is very clear. 

This is not just "faux cold" or surface cold. The -6c to -12c 850s are also edging closer to us again. Although the GFS 6z extends the surface cold slightly, it gradually mixes out the 850s during the next 5 days as can be seen by comparing the T+6 and T+120 charts below.  Whether this will actually happen is open to debate. As long as the upper flow in the Atlantic remains weak and the HP and cold block remains strong, to me, there seems to be very little indication that this pattern will be shifted during the next week or so. I feel that we may see both the surface temperatures and the 850s remain stubbornly low and remember this is mid-January when surface cold is much more difficult to shift (I feel that the UK's forecast max temps for the next few days will be steadily downgraded in the next few forecasts).

GFS Jan 17th 6z:                                          Surface temps T+6                                     850s T+6                                         Surface temps T+120                                      850s T+120       

                                                        

Please note: I thought that I copied the image address across for all 4 GFS charts in the same way but the 2 "850s" remain frozen but the other 2 are auto updating - can someone please advise me via a PM - thank you)

 

MetO 0z Fax Charts:                                       0600 Tuesday                                        0600 Wednesday

                                                      

In my last full report on Sunday evening (on page 269) I pointed out what I felt were two crucial periods. The first is almost over - the Sunday to Tuesday transition from temporarily slightly milder back to colder conditions (albeit pretty mild further north and in Scotland). I felt that the then D7 to D10 period might be very important - this is now D5 to D8. This was the next change with a wide range of options.Now, let's assume that the model consensus is at least partly right in indicating a more zonal flow in week 2. Unless the Jet Stream really intensifies again and comes straight at us (which is quite possible) the stronger than previously anticipated Euro cold block (not by me!) should put up a pretty big fight. This could give us at least several days of classic "battleground" conditions in our vicinity around the D7 to D10 period. Some snow is a possibility with this set-up. I am not going to go beyond  D10.

Please note that this is purely my personal view. I am NOT trying to do a "ramp" but I believe that there are still exciting changes in the short-term to look out for which might have quite significant impacts later on. Watch this space!

EDIT:

@Tamara  - thank you for another excellent and very informative post. This was posted whilst I was writing my post! Readers should note that Tamara's post and mine are not at all at odds with each other. I refer more to the short term and Tamara is focusing on the signals for the broader scale pattern changes during the next few weeks.

@snowflakey - in answer to your query below, yes the Jet Stream is shown to strengthen by next week. The D7 chart you show is one model and one option and it may well verify. How strong it gets and which path it takes is still undecided. I am not saying that this will not happen - just that there could be a messy transition to the widely predicted zonal spell for week 2. I am trying to stimulate interest in the next week or so on what many on here seem to have given up on. IMHO, plenty to watch and all to play for, now, later this week, next week and beyond.

 

Edited January 17, 2017 by Guest

[TEITS]

Despite the 06Z GFS and GEFS I still remain unconvinced about a return to a unsettled, zonal spell. I will add im not being biased here because actually I would prefer a mobile weather pattern.

Whilst I appreciate the efforts Tamara has made in her post I still remain sceptical. Only 4 days ago GP liked the 06Z GFS and said "It was a good road map to where we were heading". This is what that run was predicting for the 21st of Jan!

Teleconnections are the way forward for long range forecasting. However at the moment I see Teleconnections as jigsaw pieces without having a guide to put them together.

[snowflakey]

2 hours ago, Bring Back1962-63 said:

My word, it's quiet on here today. l shall try to inject a little more optimism into the current mood! As I said before, I believe that the models are continuing to seriously underestimate the depth and breadth of the European cold block. During the last 24 hours, the cold has steadily intensified again and has spread back westwards to include almost all of France. The cold, which never left the extreme east and south-east of the UK over the weekend, has been slowly but steadily pushing north-westwards in the UK. It is also slowly deepening in the south-east as the European cold continues to be advected from the continent. There are just hints that run by run, the models are extending the period of this continental "drift" beyond next weekend.

Brilliant post, even a slow dull person like myself understood it. Just a little concerned with the amount of jet energy going over the top of the high

Edited January 17, 2017 by Polar Maritime
To shorten quote.

[Interitus]

5 hours ago, Tamara said:

So to summarise the above catalysts, MJO tropical convection initiates the wave train, but it is the poleward extension of the meridional (amplifying) momentum transport that triggers the response of the mountain torque in the extra tropics and causes sudden switches in regional hemispheric jet stream and synoptic patterns.

Decreasing atmospheric angular momentum removes westerly wind momentum from the atmosphere and serves to build anomalous ridges from the sub tropics to mid latitudes starting in the Pacific.

Anomalous ridges serve to decrease atmospheric angular momentum, chicken or the egg?

AO chart and AAM chart for comparison -

Not just time periods, the December trends of AAM and AO match closely.

The problem with an all tropics and mountain torque explanation is that it is as if extratropical baroclinicity doesn't even exist.

Forecast waves and archives can be monitored at this site for evidence - http://atmos.msrc.sunysb.edu/research/climate-dynamics-and-variability/wave-packets/

 

Edited January 17, 2017 by Interitus

[frosty ground]

A bit of wintryness for Wales.

[Ali1977]

At 120 the WAA is coming in from the SW and looks better than the the run, I think we know it won't push North enough to help but it does seem to be heading for Iceland 

Quite different to the last run with a block over us and the low being held out in the North Atlantic. This keeps us in the chiller continental air mass 

Edited January 17, 2017 by Ali1977

[Seasonality]

Stronger blocking on this run, check out the differences to LP to the north of Scotland.

 

[warrenb]

Anyone noticed we are now influenced by High pressure until  day 8 now. UKMet also builds a high back in at 144

 

[Seasonality]

Just now, warrenb said:

Anyone noticed we are now influenced by High pressure until  day 8 now. UKMet also builds a high back in at 144

 

Indeed, zonality being pushed back.

[Ali1977]

A few have said zonality may not get in so quick, a few more steps like the last one and we'd have a scandy high...very much doubt that as no METO mention at all on that possibility !! Delaying the inevitable maybe!!

[jvenge]

1 minute ago, Ali1977 said:

A few have said zonality may not get in so quick, a few more steps like the last one and we'd have a scandy high...very much doubt that as no METO mention at all on that possibility !! Delaying the inevitable maybe!!

In doing so the output is starting to show what can only be called a cold spell in the process. Nothing to be sniffed at.

[Seasonality]

1 minute ago, Ali1977 said:

A few have said zonality may not get in so quick, a few more steps like the last one and we'd have a scandy high...very much doubt that as no METO mention at all on that possibility !! Delaying the inevitable maybe!!

Just hope it doesn't set up as a Euro high which blocks Atlantic systems and keeps them parked over the UK dumping mild rain.

[Jonan92]

Do you want to fly?

[Summer Sun]

High pressure in no rush to leave if UKMO is right

[booferking]

SSW has upped its ante this run.   Vortex looks distroyed at the end of this run.

Edited January 17, 2017 by booferking

[IDO]

16 minutes ago, warrenb said:

Anyone noticed we are now influenced by High pressure until  day 8 now. UKMet also builds a high back in at 144

 

Yep, just delays the inevitable zonal period, meaning likely that any new pattern will be delayed as we move in to February. Not really that cold either after D5 for many, but if you are a UK HP fan then a few extra days is good.

D10 GFS and GEM:

That is the story of the Winter, the traverses of the PV. So from D0 to D16 on this run the PV has moved from Canada/Greenland to Russia/Siberia and back again. No forcing coming even close to breaking mid-latitude hence the heights moving with the flow allowing little opportunity for anything other than transient colder uppers.

D16 

A delay to the zonal period as the High holds on is rarely good news when there is no inclination for heights to build north; the last few years winter killers have been the highs to our east, allowing the PV to circulate to our north. So poor developments from the models if we want a quick trop led change. We really do need the SSW or the forcing from other background signals. As the experts have eluded to these can pop up in the models at around D11-13 when they have not been signposted in previous runs, so we have that as a possible get out clause, though as it stands the next 16 days are rather average.

[chris55]

A rather interesting period of model watching coming up I reckon. 

UKMO 144 highlights the NH pattern is certainly not your average zonal train with the PV displaced out of Canada.

Add an invigorated MJO and a potential SSW into the mix and who knows what cold treats we could be looking at as we move into February!

 

[bluearmy]

29 minutes ago, booferking said:

SSW has upped its ante this run.   Vortex looks distroyed at the end of this run.

That's not the vortex  - its the temps 

you need to view the height charts for the vortex 

instantweathermaps is a good site 

[chris55]

4 minutes ago, Ali1977 said:

I'm not making comment on this but some info ref SSW

Nice to get confirmation GLOSEA is also seeing this potential SSW.

Timing is just about early enough to have some impact on winter, rather than spring.

Lets hope if it comes off we get a meaningful down-welling.

[nobble]

A late SSW perhaps a march snow event to rival late march 2013 ???

[bluearmy]

The trend to delay the onset of zonality the further se you are continues. However, still no strong sign it won't arrive over most of the UK by next weekend 

the evacuation of low heights from Canada well trailed and ties in with the invigorated Atlantic as the little chunk of vortex is forced into the nw Atlantic rather than e Canada 

will be interesting to see if ecm op is interested in delaying the Atlantic a bit longer - we could be looking at a repeat of late Dec when the zonal train became a couple of coal wagons  before the upper ridge re established ! 

[mb018538]

10 minutes ago, bluearmy said:

The trend to delay the onset of zonality the further se you are continues. However, still no strong sign it won't arrive over most of the UK by next weekend 

the evacuation of low heights from Canada well trailed and ties in with the invigorated Atlantic as the little chunk of vortex is forced into the nw Atlantic rather than e Canada 

will be interesting to see if ecm op is interested in delaying the Atlantic a bit longer - we could be looking at a repeat of late Dec when the zonal train became a couple of coal wagons  before the upper ridge re established ! 

Good point bluearmy - I mentioned this yesterday, in that the last attempt at a zonal spell in December didn't amount to much at all. Maybe this will be the same. It already appears to be stalling somewhat - here in the SE it appears nothing will affect us until next Monday now.

[IDO]

7 minutes ago, bluearmy said:

The trend to delay the onset of zonality the further se you are continues. However, still no strong sign it won't arrive over most of the UK by next weekend 

the evacuation of low heights from Canada well trailed and ties in with the invigorated Atlantic as the little chunk of vortex is forced into the nw Atlantic rather than e Canada 

will be interesting to see if ecm op is interested in delaying the Atlantic a bit longer - we could be looking at a repeat of late Dec when the zonal train became a couple of coal wagons  before the upper ridge re established ! 

The difference this time is we have a MLB over the US/Canada NW from around D9 to past D13 (onwards?):

This times with the PV on its journey back to our NW. If this is correct (and it has been well modelled) then a return of the Azores Ridge looks unlikely in the medium term. That set up looks a zonal UK regime to my untrained eye.

[nick sussex]

Some  differences between the GFS and UKMO over eastern Canada which results in the UKMO being flatter downstream. In the grand scheme it probably won't make a lot of difference to the eventual flattening of the high. The more important aspects of the outputs will be in relation to whether they develop an amplified central/east troughing later in the USA to help angle the jet more se'wards and remove any attempt by the Azores high to ridge in and set up shop.