Model Output Discussion - Winter arrives

[mushymanrob]

Slight developments appear to be emerging for later this month. But in this timeframe theres still no strong Scandinavian high nor Easterlies other than a possible transient feature.
A mean North of Westerly upper flow, a negative pressure anomaly over us, means unsettled and temperatures often below average, but the usual Westerly based pattern.
There is however, high pressure building over Western Siberia and extending towards Scandinavia. So theres very little chance of an Easterly based cold spell in the first half of December (other than a possible 24/36 hour affair) - there are developments that may well bring a proper cold spell later this month. And a blocking high over Western Siberia may help disrupt the SPV.

For coldies - plenty to be optimistic about, but unlikely before mid month, going off these charts.

 

[nick sussex]

The GFS 06 hrs run eventually gets to the sharper upstream trough.

Earlier though it now develops a small wave on the 00hrs run into a shortwave this complicates  the picture .

You can see this shortwave leaving Newfoundland at T96 hrs , this wasn’t there on the 00hrs .

This flattens the pattern in the mid North Atlantic temporarily.

So the uncertainty continues !

 

 

Edited November 29, 2021 by nick sussex

[That ECM]

On 29/11/2021 at 10:58, nick sussex said:

The GFS 06 hrs run eventually gets to the sharper upstream trough.

Earlier though it now develops a small wave on the 00hrs run into a shortwave this complicates  the picture .

You can see this shortwave leaving Newfoundland at T96 hrs , this wasn’t there on the 00hrs .

This flattens the pattern in the mid North Atlantic temporarily.

So the uncertainty continues !

 

 

Control makes less of this at t96. 

[Nick F]

To be honest, think the GFS last few days has been too hasty to block the Atlantic and bring us under a Scandi high influence, if it is the MJO wave propagation that is driving this signal. Would think more toward mid-month the MJO lag would work in our favour.

The TPV looks like coupling with the SPV which is strengthening down in the lower strat - so a lot of upper flow energy trying push towards us from the west as we head into early December. BUT ... Block signal in the ens Scandi to the Urals, cold surface high at first before building aloft with an increase in +ve heights to become a block, looks to force the jet SE over/near UK on into southern Europe. As long as we stay the cold side of the jet most the time - there could be some wintry interest - especially for the north - where it can tap into colder air from the east. Then perhaps as we head towards mid-month, it could become more favourable for the Scandi/Urals block to extend further west and we all get colder.

Edited November 29, 2021 by Nick F

[Froze were the Days]

Don't like the recent trends of the ECM in regards the Scandy High - from going from close but no cigar with cold on the near continent we're trending to having slow moving low heights close to the country and any real cold removed well to the north east. Yuck!

[damianslaw]

33 minutes ago, IDO said:

Not a million miles in design from the ECM:

ECM 0z>  GFS 06z> 

Variations on this theme, with obvious differences at this range, in the components within the pattern (distribution of energy, etc). Nothing too bad as we enter December IMHO.

Alot of cold ejected into the NW-SE aligned jet.. as we saw this weekend we have much colder air to our north at this stage in the season than for many a recent year.. heights to the SW and NE may lock us into a cold trough cold zonality scenario as some call it..

[nick sussex]

2 minutes ago, That ECM said:

Control makes less of this at t96. 

But it still throws a spanner in the works as the main upstream trough is flatter initially .

I think the best outcome possible in the more reliable timeframe given the overall outputs is for trough disruption through the UK and then it’s really how much cold air that can engage .

If you get the jet running se you can squeeze out some wedges to the ne .

 

 

[Dennis]

Good Monday all

dont give up

[Anthony Burden]

21 minutes ago, Nick F said:

To be honest, think the GFS last few days has been too hasty to block the Atlantic and bring us under a Scandi high influence, if it is the MJO wave propagation that is driving this signal. Would think more toward mid-month the MJO lag would work in our favour.

The TPV looks like coupling with the SPV which is strengthening down in the lower strat - so a lot of upper flow energy trying push towards us from the west as we head into early December. BUT ... Block signal in the ens Scandi to the Urals, cold surface high at first before building aloft with an increase in +ve heights to become a block, looks to force the jet SE over/near UK on into southern Europe. As long as we stay the cold side of the jet most the time - there could be some wintry interest - especially for the north - where it can tap into colder air from the east. Then perhaps as we head towards mid-month, it could become more favourable for the Scandi/Urals block to extend further west and we all get colder.

Hi Nick,

very good over all picture of the possible pattern that could occur in the next 10 days.My take low pressures 

tracking southeast into continent due to pressure rise in the northeast as you stated could keep us on the

cold side and mild spells could be squeezed out.

[Mike Poole]

3 hours ago, bluearmy said:

Apart from gfs op, did any ?????

UKMO op, both runs yesterday.

[Stu_London]

Models seem to be backing away from us getting too much influence from any Scandi High.

I think that was always on the cards as there had been plenty of indicators that Atlantic mobility would uptick in December. 

For me, cold snaps before Christmas are a bit of a bonus anyway and as quite a few have seen snow from this weekends storm plus another little snap from northerly later this week, we are doing ok in that respect. 

If we are going to get a Scandi High this year, lets wait until late Jan/Feb when there is likely to be a better cold pool and a better chance that it won't be blown away at the first attempt by the atlantic

[jamesgold]

I’ll take a wait until later in the month for the MJO lag, cold Christmas  

[Dennis]

latest MJO ECMWF 

[Hatewarmth]

2 hours ago, Premier Neige said:

Is it the gfs that has the habit of picking up a signal, then dropping it only to return to it later or am I thinking of a different model?

Your exactly right.  This is what’s been going through my head this morning.  
 

To much doom and gloom on here given the positive signals AND positive start to the season.  We not even in December yet

[Hatewarmth]

1 hour ago, TSNWK said:

Oh dear.. was looking a bit better early on.  But GFS teeze keeps in giving and we are left with this in week 

Way way way in FI.  

[northwestsnow]

7 minutes ago, Dennis said:

latest MJO ECMWF 

Looks low amplitude phase 7 into Dec - do we have any composites Dennis?

 

[TSNWK]

On 29/11/2021 at 12:07, northwestsnow said:

Looks low amplitude phase 7 into Dec - do we have any composites Dennis?

 

Wow! You understand that squiggle chart.. I simply have no idea. 

Edited November 29, 2021 by TSNWK

[northwestsnow]

4 minutes ago, TSNWK said:

Wow! You understand that squiggle chart.. I simply have no idea. 

My understanding is limited.. coldies want the squiggle line away from the circle in  the middle ,(or COD ) .

Higher amplitude the better, its not the be all and end all but might offer some help ,I'm sure others will offer a better commentary ,certainly regarding amplitude..

 

[Battleground Snow]

18 minutes ago, northwestsnow said:

Looks low amplitude phase 7 into Dec - do we have any composites Dennis?

 

6 and 7 phases for la Nina base in December

Green border means medium to high confidence/reliability

Red means low confidence/reliability

 

[Dennis]

20 minutes ago, northwestsnow said:

Looks low amplitude phase 7 into Dec - do we have any composites Dennis?

 

hi @northwestsnow is has to raise more after nect weekend .... take some time now

 

[SqueakheartLW]

Since we seem to have lost the Scandi high signal since yesterday

Maybe I can show you a few cold charts from the GFS Extended run instead for some fantasy cheer

Control +456 hours

P06 +714 hours

P20 +732 hours

P12 +804 hours

[Blessed Weather]

21 minutes ago, TSNWK said:

Wow! You understand that squiggle chart.. I simply have no idea. 

 

14 minutes ago, northwestsnow said:

My understanding is limited.. coldies want the squiggle line away from the circle in  the middle ,(or COD ) .

Higher amplitude the better, its not the be all and end all but might offer some help ,I'm sure others will offer a better commentary ,certainly regarding amplitude..

 

Well worth having a read of Prof. Adrian Matthews' (UEA Norwich) paper on the MJO. He's developed some great animations that show the progression of the MJO wet/dry cycles across the Pacific and the subsequent impact on mean sea level pressure across the globe as the MJO progresses. The UK is on the far right near the 60N line. He explains how the RMM wheel is used to track this progress and what the squiggle line means. The amplitude (strength) of each MJO cycle is represented by the distance from the centre of the wheel. When it's a low amplitude (weak) MJO the line stays in the COD (circle of doom) meaning it is too weak to impact global weather.

http://envam1.env.uea.ac.uk/mjo.html

[SnowBlake]

33 minutes ago, TSNWK said:

Wow! You understand that squiggle chart.. I simply have no idea. 

Just looks like spaghetti cooked and plated by a blindfolded chef. Even has burnt strands.

That aside, looking forward to snow so long as w/c 13th to 15th nothing disrupts flights out of Stansted for my winter in Latvia where snow has and is already falling. Got down to -20c to -26c during the day mid Jan 2021 for a week or so in rural parts. You don't want to leave the house for more than a minute.

A warmer weekend upcoming here though looking likely just about in double figures in most parts, or maybe just below.

Let's see come the weekend what is in store for next week.

 

[Pennine Ten Foot Drifts]

After this Thursday / Friday's brief cold incursion the models all seem to be in agreement in the medium term of a much more familiar winter pattern for the UK, Azores high firmly ensconced to our SW, any high pressure to E / NE locked away over Russia, large low pressure systems being spun up to our NW, and being driven eastwards by a strong flat jet. In my experience once this pattern takes hold (as the models are currently suggesting that it will) then it can take quite a while to break free from it, and whilst I don't want to be Mr Gloomy (from a cold perspective) it wouldn't surprise me at all if we're soon in the 'lets see what the New Year brings' mode of model watching...........

[Severe Siberian icy blast]

1 hour ago, Dennis said:

latest MJO ECMWF 

Low amplitude 6/7 id say ideally we want mid amplitude minimum to have an impact on the jet waves but out of the COD is good, the wedges we see atm is not in anyway linked, the wedges are primed because of the angle of the jet, the deep cold building and the position of the vortex pieces 

Im setting myself up for a fall here by the pros please correct if wrong 

Edited November 29, 2021 by Severe Siberian icy blast