Model output discussion - the beast arrives

[Catacol]

9 minutes ago, Djdazzle said:

Low pressure coming up from the south against a block doesn’t always get corrected south over time.

 

The issue is that the block is gone. Cold air is left behind which will put up some resistance, but without a pressure differential to act as a trampoline it doesn't bounce, disrupt and slide enough.

A lot of people are enjoying snow today which is great and we will have a day or 3 more of it, but it could and should have been so much more!

[Frostbite1980]

What amazes me is how long it took for the high pressure to get up to Scandinavia but then seemingly shoots straight across Greenland to eastern Canada in a matter of 2 or 3 days! It’s almost like right the U.K. has had their 5 days of cold and snow (for some) now it’s time to move on  quite unbelievable really!

Edited February 27, 2018 by Frostbite1980

[Man With Beard]

2 minutes ago, Catacol said:

The issue is that the block is gone. Cold air is left behind which will put up some resistance, but without a pressure differential to act as a trampoline it doesn't bounce, disrupt and slide enough.

A lot of people are enjoying snow today which is great and we will have a day or 3 more of it, but it could and should have been so much more!

Looking quite similar to 2009 now apart from a colder easterly doing more damage on the east coast? Strong trop response to SSW - quick Scandi High - low pressure combining with cold pool eventually leading to low pressure circulating the UK and a slow snowy breakdown (I recall nearly getting stuck on Haldon Hill that week, totally unforecast, maybe same could happen there again!) but no prolonged cold.

Nearly a 1991 but our cold pool won't interact will the Atlantic low to keep the cold locked in like it did then, it would appear.

[phil nw.]

2 minutes ago, bluearmy said:

If we discard the gem (which has been a bit wierd on this upcoming period) then the cross model agreement is on the breakdown getting to north midlands at least. Let’s see what ec op brings and then make a call on this. 

Yes it looks that way blue.With the block fading west some sort of change looks inevitable,maybe there may be enough of it left to keep the cold further north hanging on a while longer and this may show on the later ECM.

Recent ens pointing a cyclonic few days next week,still below average temp.wise but not enough for any snow interest away from the usual favoured locations from what i can see currently.

@Catacol

Yes i agree disappointing to see the block going  west so quickly without at least resting a few days over Greenland which often happens after the Scandi high regresses.

 

[nick sussex]

In terms of the cold pool, a few days back there were concerns it might miss the UK because of the quick evolution to the omega block.

There seems to be a myth surrounding Scandi highs that they can last for weeks, simply not the case.

To extend the cold you need a signal to retrogress the high , the issue isn’t that signal but it’s taken the high too far to the west .

Thats always a risk , a west based negative NAO .

But going forward it’s premature to assume that the weekend is game over, all the outputs still have the jet tracking to the south.

Edited February 27, 2018 by nick sussex

[Jason M]

37 minutes ago, Djdazzle said:

 think if the breakdown pans out as shown (and it is STILL an if at this stage), we will have learnt a few things:

Cold air can be easily displaced by warm air.

Low pressure coming up from the south against a block doesn’t always get corrected south over time.

The GFS cannot just be dismissed as rubbish just because it isn’t showing what people want.

Anyway, really hoping for an ECM trendsetter later on!

 

 

 

 

 

I think your post should be put at the top of each new Winter thread.

It is disappointing tbh looking at the charts for the weekend because the GFS looks like being correct in broad terms to bring the low north rather than northeast through France despite most of us thinking it unlikely. It does show that no output should be completely disregarded especially if its only a week away (however outwardly outlandish)!!!

Still lots to enjoy this week though with more snow in the short term.

 

Edited February 27, 2018 by Paul

[bluearmy]

The surface low heads in a cyclonic fashion ne and then west in response to the phasing of the upper cold pool and upper Azores trough. If it were just one system then we may well all have stayed on the cold side. But the west based neg NAO tilts the trough sw/ ne and we’re done for ! 

i posted earlier as to why gfs probably got to this faster than the other models. Mind you, a win is a win !! 

[high ground birmingham]

45 minutes ago, jayb1989 said:

How quiet it is in here tells you all you need to know about current output beyond the weekend.

In fairness the breakdown has been managed pretty well by GFS in my opinion, it’s always gone with milder air making inroad since early last weekend.

Quite baffling how some on here were reluctant to except what model outputs were conclusively showing, choosing to instead believe the cold air would not be as easily moved.

It is worth noting that a few runs have hinted at something colder perhaps coming back in at some point, but with March now fast approaching and the really cold air on it’s way out, i for one will be hoping for an early spring.

Still a nice event Thursday/Friday and possibly Saturday to enjoy.

This is a rather bizarre post considering the breakdown hasn’t yet occurred. There’s still scope for further changes in the output. A correction of 100 miles south is pretty much what’s needed for most people.

Scotland and N England never really lose the cold air by the way.

[BLAST FROM THE PAST]

Deep deep uppers will go....but I must be looking at different models.  I won’t be expecting my Spring bulb display anytime soon

 

BFTP

[Mike Poole]

32 minutes ago, Catacol said:

The issue is that the block is gone. Cold air is left behind which will put up some resistance, but without a pressure differential to act as a trampoline it doesn't bounce, disrupt and slide enough.

A lot of people are enjoying snow today which is great and we will have a day or 3 more of it, but it could and should have been so much more!

I wonder if the block is not quite as gone as it was once modelled to be - by the GFS which was the first to make inroads into the UK cold pool on Friday's 18z run, which I can recall making some derogatory remarks about.  Here's the chart for early Friday morning from that run:

Compare today's 12z at the same time:

The block over Greenland  looks stronger (brighter yellows).

The latest models extend the cold spell into Saturday, but that is still four days away. While I agree that the cold will most likely lose out in the South, I don't think it's a certainty.

Edited February 27, 2018 by Mike Poole

[johnholmes]

re this comment

Some fair points there. GFS trumped the lot including the great MOGREPS!! And it didn't overblow the low at all - it was spot on (I got that one wrong)

I don't think we actually see MOGREPS do we?

Of not then how it performed is how some have interpreted how Exeter have worded their forecasts I suspect. They 'may' not have followed what that model said, do we know for sure?

[nick sussex]

I think what’s happening here is irritation by some members depending on where people live.

It would of course be great if the whole UK could remain cold but if that’s not to be it would still be good if parts of the UK remained cold.

For two reasons if the cold isn’t lifted out from more central and northern areas any further trough disruption could tap into that.

And secondly coldies are supposed to be a bit more united , yes I know everyone wants the snow but surely it’s possible to still feel happy for other UK coldies if they continue to see more.

Am I expecting too much here!

The GEFS by the way still have some interesting solutions .

 

[Methuselah]

8 minutes ago, BLAST FROM THE PAST said:

Deep deep uppers will go....but I must be looking at different models.  I won’t be expecting my Spring bulb display anytime soon

 

BFTP

I'm minded to agree with you there, Fred: the 'warmest' temps I've seen forecast for the early part of next week are mostly 5s and 6s...So hardly warm for the start of March...

As we often like to say on here: It ain't over till Adele sings!

 

Edited February 27, 2018 by Ed Stone

[nick sussex]

I see GP is in the house.

I know he can’t say too much because of his job but a question if I may.

Looking at the MJO this has recently gone through phase 8 and into 1 .

Given the time lag is it possible there’s a bit of a conflict between the recent warming as in where it wants to put blocking .

And what the trop effect should be given the MJO.

 

 

[Derecho]

Time to update the new trackometer again. Not much change in the 06z ensembles in terms of the overall synoptic pattern, but areas in the north of England appear likely to hold onto the cold maximums until Sunday now.



Okay no turnaround to keep us all in the cold air but its still a possibility I think. 2 days ago we thought Friday could be rainy for the south, yet it looks like a snowy day now. Many of the ensemble members show the Azores low moving to the east of the UK in the middle of next week to allow some colder air back in. Could there be a chance we hold on to our continental airmass for most when this transition with the Azores low happens?

That is what I hope anyhow, even if its a longshot.

Edited February 27, 2018 by Quicksilver1989

[nick sussex]

1 minute ago, Quicksilver1989 said:

Time to update the new trackometer again. Not much change in the 06z ensembles in terms of the overall synoptic pattern, but areas in the north of England appear likely to hold onto the cold maximums until Sunday now.



Okay no turnaround to keep us all in the cold air but its still a possibility I think. 2 days ago we thought Friday could be rainy for the south, yet it looks like another cold day. Many of the ensemble members show the Azores low moving to the east of the UK in the middle of next week to allow some colder air back in. Could there be a chance we hold on to our continental airmass for most when this transition with the Azores low happens?

That is what I hope anyhow, even if its a longshot.

QS can I just say thanks .   I love these charts you do. 

And in terms of the GEFS they certainly don’t shout game over. Anytime the jets tracking to the south you’re always in the game.

[Glacier Point]

11 minutes ago, nick sussex said:

I see GP is in the house.

I know he can’t say too much because of his job but a question if I may.

Looking at the MJO this has recently gone through phase 8 and into 1 .

Given the time lag is it possible there’s a bit of a conflict between the recent warming as in where it wants to put blocking .

And what the trop effect should be given the MJO.

 

 

Nope - I would be concentrating on the GWO, low amplitude La Nina type pattern. Broadly suggestive of the blocked type pattern in the NE Atlantic. 

[nick sussex]

Just now, Glacier Point said:

Nope - I would be concentrating on the GWO, low amplitude La Nina type pattern. Broadly suggestive of the blocked type pattern in the NE Atlantic. 

Thanks yes I know you prefer that measure rather than the MJO.

So blocked ne Atlantic sounds good. 

[Philbill]

There are some people in this thread who are too quick to push the cold air out of the way, particularly if its the GFS showing it? This model has not performed that well in this current cold spell. It was not that long ago it suggested on Thursday there would be a low up to Southern Scotland. There were posts of "game over" etc and I am not just saying this is because its "not what I want to see". I believe this is far from nailed on as I said earlier and there are more twists to come. Forecasting a lows track is difficult when the parameters are "normal". The current situation is far from normal so just sit back enjoy any snow you get and lets see how it develops

 

[nick sussex]

What’s been quite remarkable about this spell is some of the dew points .

The air is so dry , absolutely no sign of frost here this morning even though the temp got down to -6c.

[bluearmy]

The gefs still appear to be playing with another downwelling wave later next week 

If we can keep the remnants of the deep cold close to Scandi then it is feasible that this could get here within the next ten days with a renewed amplification or a broad euro trough reforming. 

Thats probably the least likely evolution but it’s not gone away 

[Derecho]

9 minutes ago, nick sussex said:

QS can I just say thanks .   I love these charts you do. 

And in terms of the GEFS they certainly don’t shout game over. Anytime the jets tracking to the south you’re always in the game.

Thanks , I find that sometimes my interpretation of the models can be affected by my mood haha, so I thought I'd be more objective and display things in a graphical format and then discuss further if I spot anything more.

I will also include the ECM ensembles for the 18z

[Allseasons-Si]

3 minutes ago, nick sussex said:

What’s been quite remarkable about this spell is some of the dew points .

The air is so dry , absolutely no sign of frost here this morning even though the temp got down to -6c.

Dry polar continental air Nick

went to scrape the car this morning and the snow just wiped off and was very powdery,love it

the gefs mean at 180 looks good to me with the low further south than this mornings,be interesting to see that sink further south.

Edited February 27, 2018 by Allseasons-si

[nick sussex]

Just now, Allseasons-si said:

Dry polar continental air Nick

It seems funny saying how dry the air is when some parts of the UK have seen some decent snowfall.

[Mac_SE]

Two basic questions re the models for those with far more weather grey matter than me:

1. is the northerly track of Friday's low simply down to the lack of blocking, especially given the lack of jet energy?
2. given the stunning and comparable synoptics to '87 & '91, what is the big difference/reason between the sudden-ish shift of that block and those from the historic spells?

Have a broad understanding of reading the charts just not enough (yet)...

Thanks