The hunt for cold - Model discussion (late November)

[Met4Cast]

We’ve moved a step forward this morning. 

Whilst the Det runs are continuing to flip flop the theme has remained the same, high pressure building across the UK towards mid-month seems fairly likely now turning things settled, likely colder with a return of fog and frost.

The high seems somewhat likely to extend North/North-East and begin developing across Scandinavia and this is when the uncertainty once again kicks in, will we see the Atlantic shut up for long enough to get sufficient ridging and then hopefully undercutting (a la last nights models) or will the Atlantic put too much pressure on the high (overnight runs). 

EPS is steadfast in Scandi height rises, ensembles fairly solid on temperatures dropping underneath a cold high, I’m still 50/50 on the deep cold scenario.. 

[BLAST FROM THE PAST]

10 minutes ago, Weathizard said:

More amplification trending early again...

 

0z 

6z

Yes agreed. Expect that LP to dive NW/SE 

 

BFTP

[Stuie]

Better from the GFS, cold air much closer to the east, better Atlantic ridge and cold not filtering into central US.

 

[SMU]

For those newish looking in- subtle differences play out a big change-

At around 156 we want the secondary ridge more amplified than the first ridge in the atlantic which steers the low more SE

Here the 06z V 00z is much better

[frosty ground]

The jet is looping around the block if we can get that to swing back towards the UK then we can drag more unstable air with the cold air

 

if not the high topples quickly

[Ice Day]

Not the greatest of overnight runs (although the ECM was a warm outlier), but the 6z is looking vastly better vs 0z.  At 216 there's a very big cool down going on to our east. Obviously fine details are irrelevant this far out but good to see all the same!

  

[feb1991blizzard]

8 minutes ago, Steve Murr said:

For those newish looking in- subtle differences play out a big change-

At around 156 we want the secondary ridge more amplified than the first ridge in the atlantic which steers the low more SE

Here the 06z V 00z is much better

And the third ridge is important as well, the one about to be thrown up towards Greenland at around 222, without these, the pattern will just collapse.

A few attempts needed here to get cold in.

Edited December 2, 2018 by feb1991blizzard

[ArHu3]

Another big Aleutian low and a Siberian high forming, so more chances for a ssw later on

 

[frosty ground]

The jet is a wining back from Norway to the uk a good sign now just need some energy to sneak under the block

 

alas not to be on this run another serge of high pressure builds and the jet can,t break through on a southerly track

still it would be nice and clear

Edited December 2, 2018 by frosty ground

[Singularity]

I concur with those who foresee a multi-ridge-build route to a ‘proper’ cold feed.

Theres enough broad-scale support for ridging to shift the Atlantic troughs away from the UK by day 7 or 8, but further amplification is then required to take that ridge further north.

This is where severe strat vortex disruption coupled with a fast propagating MJO can come in very handy.

[frosty ground]

Look at the jet on the 300 hour chart straight down the Canadian coast to the states then loops strict back north

 

not it’s standard path

[feb1991blizzard]

The stratospheric charts are an absolute stonker.

How often you see a chart right at the top of the strat like that on December the 2nd.

https://www.instantweathermaps.com/GFS-php/strat.php?run=2018120206&var=HGT&lev=1mb&hour=384

Edited December 2, 2018 by feb1991blizzard

[northwestsnow]

Heights being sucked into the Atlantic as mused earlier

[Leo97t]

Yes the strat charts are unbelievable and no vortex over Canada by the end of the run. Would be thrilled to see that with an northerly likely following

[Methuselah]

Well the signal for blocking is getting stronger, but its position remains a bit of a mystery: Will we see a short spell of snowy weather (most likely in the East) or will it settle down for a foggy, frosty few days?

I'll take either!

[Duane S.]

21 minutes ago, Singularity said:

I concur with those who foresee a multi-ridge-build route to a ‘proper’ cold feed.

Theres enough broad-scale support for ridging to shift the Atlantic troughs away from the UK by day 7 or 8, but further amplification is then required to take that ridge further north.

This is where severe strat vortex disruption coupled with a fast propagating MJO can come in very handy.

And me. As nice as yesterday’s aggressive ridge up northwards was, it didn’t really have a lot of support. So not surprised to see that dropped today.

3 ‘mini ridges’ in quick succession should do the job and looks much more plausible.

Whether we were to thenend up with UK high or an easterly courtesy of a NE block remains to be seen of course.

[bluearmy]

Housekeeping on the clusters 

there is a 50/50 split on the less amplified op against previous ops

beyond day 10, these two clusters go to six again (max 25% support) so still no reliable guidance 

[ALL ABOARD]

The para is a beautiful run. 

[SMU]

Excellent FV3 sees the best case scenario for the block

it also runs out a full retrograde to Iceland...

[snowray]

7 minutes ago, Steve Murr said:

Excellent FV3 sees the best case scenario for the block

it also runs out a full retrograde to Iceland...

Yes indeed Steve. 

Is this the heart shaped Icelandic high that you talk about sometimes by any chance?

[blizzard81]

5 minutes ago, Steve Murr said:

Excellent FV3 sees the best case scenario for the block

it also runs out a full retrograde to Iceland...

The GFS parallel is starting to remind me of the gfs of yesteryear - throwing out winter nirvana charts during week 2 that don't materialise. Let's hope this upgraded version is a little more accurate. 

[SLEETY]

loving the gfs parallel again,with the deep purples appearing at the end heading South,maybe we might see the black hole appearing when 850 hpa  air is 474 

Edited December 2, 2018 by SLEETY

[Mike Poole]

FV3 at T288, brings in the cold air nicely

[nick sussex]

It’s a shame the ECM decided to play Scrooge this morning .

Better news from the GEM and GFS06 hrs run.

The latter does bring some trigger shortwave drama into the mix ! There’s still model uncertainty within the day 6 timeframe with the degree of upstream amplification so a lot still needs to be resolved this evening .

PS where have all the screen names at the bottom of the page gone?

 

Edited December 2, 2018 by nick sussex

[SMU]

10 minutes ago, snowray said:

Yes indeed Steve. 

Is this the heart shaped Icelandic high that you talk about sometimes by any chance?

Its lovely but not the shape High

Thats Greenland & Scandi high together with a low diving south in the middle...