Model output discussion - proper cold spell inbound?

[Banbury]

Some cracking ENS and it seems if we don't get it from the E we then get it from the NE or in some cases both

[tight isobar]

3 minutes ago, karlos1983 said:

Well well well, many purbs want an arrival of cold in a weeks time! things appear to be gathering a pace!

and then there is the ECM ens, also trending colder 

EDIT: in fact that's the best set we've seen yet! hardly any mild runs!

Cracking set..in the form of direction!!!

[Met4Cast]

Probably struggle to see a better panel than this one

Absolutely solid support for high latitude blocking. Placements of the high varies of course, but the broad pattern is great!

[jvenge]

5 minutes ago, shaky said:

Good stuff i suppose could bring in cold later but could also bring in cold earlier!lets see where 12z goes!!

Earlier, Later, not at all, less extreme, more extreme. You name it :-)

 

[Fozfoster]

Ok, looking good for a Feb 1991 style easterly so i will name two more slabs.

[Big Snow]

Hi all, I only have a very basic understanding of the charts and was wondering, what's the difference between the 'op' run and the 'control' run? Is there a difference in reliability etc? Cheers and keep up the great analysis.

[Frosty.]

The potential is so exciting in the weeks ahead, here is a sample from the GEFS 6z..prepare for a very cold spell appears to be the message from the latest model output, hopefully a prolonged one!! 

[Scandinavian High.]

4 minutes ago, tight isobar said:

Cracking set..in the form of direction!!!

Very cold -15  all trending in right direction..

[Badgers01]

19 minutes ago, BLAST FROM THE PAST said:

Well seeing as Feb 91 was exceptional....possibly not.  But if todays runs are correct it’s going to give it a darn good go.  

 

BFTP

The uppers were around -16 for southern England during the peak of that event, not any output yet showing them that low.

[Daniel*]

Wow what have I missed? Absolute great runs overnight, goes to show why some should treat NWP very cautiously I’m sure in 2013 there was a flip too in a short space of time. Not been this excited in years. 

[tight isobar]

1 minute ago, Badgers01 said:

The uppers were around -16 for southern England during the peak of that event, not any output yet showing them that low.

Running through p-stamps..and the travel of ens(6z)...-16 upper values will likely rear there heads...as we evolve through suites!!!!

[Daniel*]

The ‘upgrades’ keep rolling from the EPS the NAO is even more negative than yesterday. Could we be on the cusp of s big one? I think so.

[Trom]

5 minutes ago, Big Snow said:

Hi all, I only have a very basic understanding of the charts and was wondering, what's the difference between the 'op' run and the 'control' run? Is there a difference in reliability etc? Cheers and keep up the great analysis.

The operating run has greater resolution.

The control uses the same initial data as the op but is run in low resolution.

The ensembles are run in low definition but have tweeks to the starting data.  Purpose of the ensembles is to add support to the results of the operating and control runs.  The ensembles can also be used to identify clusters which give us an idea of future trends.  What they can't really be used for is analysis of individual perbs with some kind of hope that they will materialise.

[Met4Cast]

Just now, Trom said:

The operating run has greater resolution.

The control uses the same initial data as the op but is run in low resolution.

The ensembles are run in low definition but have tweeks to the starting data.  Purpose of the ensembles is to add support to the results of the operating and control runs.  The ensembles can also be used to identify clusters which give us an idea of future trends.  What they can't really be used for is analysis of individual perbs with some kind of hope that they will materialise.

The Control is the same resolution as the OP I believe 

[Derecho]

P1 goes absolutely bonkers and develops an extreme -NAO, what do I make that to be? a 110mb difference between the Azores and Greenland?

RIP Greenland Vortex



But seriously send the WAA to Greenland and watch the rest that follows. This run is extreme with -15C uppers crossing the UK, but there are plenty of other awesome Greenland highs in there which IMO would be better for a long term cold spell then a short lived easterly, February 1991 and January 1987 had much colder uppers btw.



P2 is perhaps even more extreme with a gigantic high to our north which develops as early as T168 then keeps us in a bitterly cold easterly until T384....

Edited February 13, 2018 by Quicksilver1989

[Daniel*]

2 minutes ago, Trom said:

The operating run has greater resolution.

The control uses the same initial data as the op but is run in low resolution.

The ensembles are run in low definition but have tweeks to the starting data.  Purpose of the ensembles is to add support to the results of the operating and control runs.  The ensembles can also be used to identify clusters which give us an idea of future trends.  What they can't really be used for is analysis of individual perbs with some kind of hope that they will materialise.

No same resolution as OP and it’s not started using same initial data I’m sure different starting data. The ensembles only past 10 are they really low res I believe. 

[stodge]

Morning all

As the old song has it "there are three steps to heaven" and the same is true if considering the path to a very cold and snowy outlook so let's look at the three steps:

1) Build the block - some runs a few days ago had the Azores HP ridging north to the west of the British Isles and then NE into Scandinavia. This was, to paraphrase another song, "the motorway to cold". A more scenic route has the HP moving NE through the British Isles and into Scandinavia and that was advertised widely in last evening's output.

2) Get it in the right shape - HP over Scandinavia only works in terms of cold if it is positioned and oriented correctly. It's perfectly possible to have a HP oriented so feed warmer SE or S'ly winds across the British Isles so the right shape (aided by lower heights over southern and central Europe) is a necessity.

3) Find the cold air and bring it in - it's no use having an E'ly if there is no cold air to advect and that's the important part. Ensuring the HP is far enough north so the cold air is not advected too far south and making sure we are drawing our air source from a cold rather than warmer SE source is the most important aspect of the evolution.

So is heaven on the horizon this morning, close at hand or is it going to be purgatory for the coldies with France in the freezer and Britain balmy or chilly ?

Today I'm looking out to February 23rd and starting with ECM 00Z at T+240:

The Azores HP builds across the British Isles and over to Scandinavia and draws in an increasingly strong and cold E'ly feed through next week. One suspects the blast of colder air might dissipate as the HP looks to be orienting slightly more to the ESE but not much.

GEM 00Z OP at T+240:

A slightly different evolution from GEM which moves the HP core to Iceland so more of a ENE'ly flow. The first puch of very cold air passes just to the south but the weave of frigid air approaching from Scandinavia looks to have our name on it.

GFS 00Z OP at T+240:

More anticyclonic and perhaps not as cold. A large HP sits to the NE covering the North Sea and a noticeable SE'ly flow covers southern and western England but it's dry at this time. Further into FI, the HP trends NW toward Greenland and forms a substantial HLB. There is one pulse of very cold air which crosses the British isles but at the very end of FI more than a hint of something much warmer.

GFS 00Z Control at T+240:

Very anticyclonic but with the coldest air just passing to the south of the British Isles. The evolution further into FI is a coldies' nirvana - the HP retrogresses to Greenland and an LP moves east into northern France drawing in some very cold air from the east.

The GEFS at T+240 are one of the strongest for cold I've seen for a long time:

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=240

Life has moved on and we now have the GFS 06Z OP at T+234:

Very anticyclonic but with the coldest air just to the south of us at this time. The evolution into far FI is more complex with a slackening of cold air and a more SE'ly flow.

GFS 06Z Control at T+240:

Not much for fans of cold to complain about. The evolution into far FI is frankly as good as it gets if you want cold or snow.

In conclusion, one of the strongest suites for cold I've seen for a long time but to stress a) it's not a done deal and b) for fans of snow there are still hurdles to jump. Some evolutions are more anticyclonic initially so the journey to snow is delayed further while others bring in colder air more quickly. It's hard to see how this can upgrade much further so it's now about consistency, severity and longevity. Some keep any cold air short-lived and return to a much milder SE'ly airflow while others are much more bullish about a 7-10 day severe spell.

[ICE COLD]

This set of ensembles from the GFS 6z are stunning . And the 00z. @feb1991blizzard Will be loving ? these large ?. 

[Big Snow]

5 minutes ago, Daniel* said:

No same resolution as OP and it’s not started using same initial data I’m sure different starting data. The ensembles only past 10 are they really low res I believe. 

Thanks for explaining, much appreciated.

[karlos1983]

13 minutes ago, ICE COLD said:

This set of ensembles from the GFS 6z are stunning . And the 00z. @feb1991blizzard Will be loving ? these large ?. 

 

Where on earth is he!! Not seen him post for at least a week! I'm sure he's enjoying the output like the rest of us anyway! 

Edited February 13, 2018 by karlos1983

[ICE COLD]

9 minutes ago, karlos1983 said:

Where on earth is he!! Not seen him post for at least a week! 

PM you mate 

[jvenge]

Hard to spot the difference between the 0z and 06z mean anomalies.

[Summer Sun]

Bitterly cold control from GFS 06z

[bobbydog]

4 minutes ago, Big Snow said:

Thanks for explaining, much appreciated.

erm thats not correct. the operational run is the unaltered high resolution run. the control is the same but with lower resolution. the ensembles are lower res but with small changes to starting conditions. if the control differs to the op, this determines that the differences in the ensembles are due to lower resolution rather than starting conditions.

if that makes sense....

[Singularity]

What really catches my eye is how much the depth of cold we receive in the 8-12 day period is dependent on the strength of height rises in the Svalbard region and a bit N and/or E from there, which is one of the regions in which blocking development is most often underestimated by the models.

GEFS doing a surprisingly good job actually - considering lower resolution in stratosphere - of illustrating what's possible if we get a stronger height rise than the operational came up with.