The hunt for cold - Model discussion (late November)

[Iceaxecrampon]

12Z

Yes a default Atlantic - but a pretty impressive LP that.

[Met4Cast]

It's rare to see lows explode like that in zonal situations, it seems when they're coming up against a Scandi block models struggle to resolve where the energy is going and instead of sending it in a given direction, it holds it all together and you get dartboard lows..

This is a known GFS bias but odd to see the GEM also doing it. They never verify so it's not really a worry, given Westward adjustments in the short term what a low does at 240hrs away isn't really much of interest.

[Spah1]

6 minutes ago, Steve Murr said:

Guys stop panicking about the atlantic pushing through-

* ITS A MODEL BIAS *

 

Wait for another 48-72 hours & then see what it shows in terms of the block holding strong-

Ok will do

They just don’t seem very stable when they come along. 

[blizzard81]

I must admit I am a little disappointed with the output today. The clear trend through today on the gfs at least is for the Atlantic to break through far earlier than anyone of us would like. Indeed, the easterly doesn't even set in at all really. The exception to this is the last couple of ecm ops. We really do need to see the ecm hold firm on the easterly tonight, otherwise I feel this will be a very short lived affair indeed - much shorter lived than the last couple of ecm op runs would have you believe. 

Edited December 5, 2018 by blizzard81

[booferking]

Just now, mountain shadow said:

Boofer, you've been on here long enough to know about the GFS bias to over playing the strength of Atlantic lows.

My own gut feeling is that the lows will disrupt more and slide under the ridge. The upper air may be marginal for any associated snowfall but the best falls can come from such situations.

Another crucial ECM coming up!

My honest opinion is that the first low slides and misses us altogether but we shall see...

[AWD]

I was always under the assumption that any colder surface weather next week was always likely to be a relatively short term affair?

A precursor say, to something more notable & lengthy towards months end into January, once any forecast stratospheric impacts filter down to the troposphere?

[Methuselah]

Don't trust this horrible evolution until the Met are on board?

[Met4Cast]

1 minute ago, Ed Stone said:

Don't trust this horrible evolution until the Met are on board?

I'd say don't trust it whilst it's 15 days away, but that too..

[Seasonality]

24 minutes ago, Daniel Smith said:

Predictably the second we get into low res the low explodes and blocking melts away like butter

Improvements in the short term. Great 12z GFS. Great UKMO 12z.. ECM, over to you.

Indeed. A known GFS bias. Cold blocks are often much more resilient in reality compared to the modelling. 

[mulzy]

19 minutes ago, mountain shadow said:

Boofer, you've been on here long enough to know about the GFS bias to over playing the strength of Atlantic lows.

My own gut feeling is that the lows will disrupt more and slide under the ridge. The upper air may be marginal for any associated snowfall but the best falls can come from such situations.

Another crucial ECM coming up!

Every run is a crucial ECM tbh!

[Snowyowl9]

UKMO looks better orientated.

 

[Methuselah]

2 minutes ago, Seasonality said:

Indeed. A known GFS bias. Cold blocks are often much more resilient in reality compared to the modelling. 

True enough...But, looking on the bright side, such a wild swing by the GFS provides a great opportunity to see how the Para reacts:

 

[tight isobar]

7 minutes ago, Ed Stone said:

True enough...But, looking on the bright side, such a wild swing by the GFS provides a great opportunity to see how the Para reacts:

 

Pazza-suite..(para)

Certainly 'less bullied' via AT-progression than its horrible- little sister.

And has reckoning decipher value.

I see the mods changed my initial swipe...

Edited December 5, 2018 by tight isobar

[mulzy]

The 12z GEFS have already pushed the block westwards ~50 miles to the west at day 6.  Expect these corrections to continue...

[That ECM]

3 minutes ago, tight isobar said:

Pazza-suite..(para)

Certainly 'less bullied' via AT-progression than its gfuqhgfpjhy little sister.

And has reckoning decipher value.

Didn’t help

[SMU]

The GFS is still refining the current situation at ~96-120 West & North which deliver better blocking ~144

Note the marginal changes here-

New run on the right

Note the height of the yellow 552 Line on the second chart V 06z top chart.

What the model is resolving as we transition 144> 96 is the finer points of the long & shortwave pattern - The longwave pattern is becoming ever more amplified with increase in jet returning SW through Scandi & as that increases the force acting on the atlantic allowing it to bend further & further away from the UK.

^^ This is exactly why sliders often migrate south & west when we go from 96 > 0 in the models as they are reducing the NE component of the jet replacing it with increased SW component looping back around the High pressure

Worrying about the 12z operational to me means that people have learnt nothing about models & their capabilities / nuances over the last 5 - 10 years....

Edited December 5, 2018 by Steve Murr

[Met4Cast]

Westwards correction continues on the GFS(P) too, about 50 miles or so..

[Seasonality]

4 minutes ago, mulzy said:

The 12z GEFS have already pushed the block westwards ~50 miles to the west at day 6.  Expect these corrections to continue...

If it shifts further east does the 'correction' become a 'mistaken?' 

[booferking]

So we can call UKMO Day 5 middle ground if we use ECM,s morning run maybe thats what we should aspect to see come 11th Dec..

[Met4Cast]

3 minutes ago, Steve Murr said:

Worrying about the 12z operational to me means that people have learnt nothing about models & their capabilities / nuances over the last 5 - 10 years....

But Steve, the 6z showed the Atlantic blasting the block away.. 

Joking aside, I agree! The number of times we've seen the GFS in particular make big Westwards corrections when it comes to the Atlantic over-running blocking you'd think people would know by now, especially since it happens at least twice per winter.

GEFS mean further West, too!

[DanBaynes]

1 minute ago, Seasonality said:

If it shifts further east does the 'correction' become a 'mistaken?' 

A mistake not at all, but over the last 10 years of model watching I and others have noticed a correction west on the models the nearer we get to t0 is often seen

[Mike Poole]

FV3 T144, great blocking signal, and also the shape of the low pressure to our west looks good with the angle to go under, hopefully.

Jet stream at same time reinforces:

[I remember Atlantic 252]

44 minutes ago, Ed Stone said:

I reckon the GFS has an ongoing contract with WINMAU? Bloody dartboards!

Starts then too! qualifying day before

[snowray]

FV3 12z looking pretty decent, again this is better than its 06z run with colder air edging west.

[Methuselah]

4 minutes ago, Seasonality said:

If it shifts further east does the 'correction' become a 'mistaken?' 

I think I prefer the term 'adjustment':