Model output discussion - cold proper on the way?

[Mike Poole]

1 minute ago, Daniel Smith said:

That would of course mean the ICON has been consistently rubbish..

I think that may be the final verdict on that models performance in the run up to this event or non-event, let's see!

[Runcible Spoon]

4 minutes ago, MattStoke said:

That model is so poor. It gave me and large parts of England a full on snow even earlier in the winter, and there wasn't a flake away from the hills. Often way off on temperatures too. It's pretty useless.

But are the GFS snow maps any more trustworthy three days out?

[Met4Cast]

Just now, Runcible Spoon said:

But are the GFS snow maps any more trustworthy three days out?

The GFS snow maps aren't trustworthy even 6hrs out..

[Jason M]

3 minutes ago, abbie123 said:

Big snow event as front comes in to colder air ..

Only my opinion but when I look back over the years I can can't off the top of my head think of a single occasion where a frontal system has come down from the NW into a not particularly cold airmass and given only front edge rain. For that reason alone I'm with Arpege / ICON on this one. I think the snow signal is being massively overplayed. If we had a fully embedded CP airmass different story, but I don't buy this (high ground maybe different story though!).

Love to be proved wrong because it looks a great chart. A short sharp deluge of wet snow on the back edge could well be on the cards though.

[Frank Trough]

4 minutes ago, MattStoke said:

That model is so poor. It gave me and large parts of England a full on snow even earlier in the winter, and there wasn't a flake away from the hills. Often way off on temperatures too. It's pretty useless.

For last March's easterly one of the arpege or HIRLAM was miles out and the other spot on (for down here). I can't remember which way round it was...

[MattStoke]

4 minutes ago, Runcible Spoon said:

But are the GFS snow maps any more trustworthy three days out?

No. It's snow accumulation charts are very poor, but it normally does well on picking up streamers. 

Personally, I go by the Euro4 model and the WRF model. Find them both to be better than the Aperge and the ICON normally. The Hirlam model isn't bad either. None are anywhere near perfect though.

Edited January 19, 2019 by MattStoke

[SMU]

Just now, MattStoke said:

No. It's snow accumulation charts are very poor, but it normally does well on picking up streamers. 

Personally, I go by the Euro4 model and the WRF model. Find them both to be better than the Aperge and the ICON normally.

& the HIRLAM

[Nick F]

15 minutes ago, abbie123 said:

Big snow event as front comes in to colder air ..

Would be careful of the GFS snow charts, always find that GFS is over-optimistic of snowfall at lower levels on back-edge of fronts with a cold northwesterly polar flow undercutting. I find it has bias to have dew points too low in the south in NWly flows until nearer the time. The 00z EC doesn't have any snow for England and Wales away from hills, Scotland could be another matter with snow to lower levels more likely.

Showers following in the northwesterly flow could fall as snow to lower levels in the north and northwest though.

Though given the front comes through at night I suppose we can't rule out wet snow in the south on the back edge as cold air undercuts the front. The air flow ahead of the front likely too mild for snow preceding.

Edited January 19, 2019 by Nick F

[MattStoke]

Just now, Steve Murr said:

& the HIRLAM

Must have read my mind. Added that at the same time you were replying 

[john mac]

4 minutes ago, Jason M said:

Only my opinion but when I look back over the years I can can't off the top of my head think of a single occasion where a frontal system has come down from the NW into a not particularly cold airmass and given only front edge rain. For that reason alone I'm with Arpege / ICON on this one. I think the snow signal is being massively overplayed. If we had a fully embedded CP airmass different story, but I don't buy this (high ground maybe different story though!).

Love to be proved wrong because it looks a great chart. A short sharp deluge of wet snow on the back edge could well be on the cards though.

Is it not more about the cold air undercutting from the north west. 528dam line just behind the front on the faxes. 

[Met4Cast]

Hard to tell but does that storm look a little North-West of where the GFS predicted it?

[Midlander]

1 minute ago, Daniel Smith said:

Hard to tell but does that storm look a little North-West of where the GFS predicted it?

Please may you clarify something Daniel if you may: For coldies we want the low further west and deeper?

[Mike Poole]

6 minutes ago, MattStoke said:

No. It's snow accumulation charts are very poor, but it normally does well on picking up streamers. 

Personally, I go by the Euro4 model and the WRF model. Find them both to be better than the Aperge and the ICON normally. The Hirlam model isn't bad either. None are anywhere near perfect though.

My experience last year with the BFTE was HIRLAM was excellent but it's only 2 days out, ARPEGE was good, ICON-EU (not to be confused with ICON global, as many still do) was awful.  Just want to get into the position that we are talking about these models predicting snowfall, so far I haven't had cause to look at any of them once!

[Updated_Weather]

2 minutes ago, Daniel Smith said:

Hard to tell but does that storm look a little North-West of where the GFS predicted it?

Interesting spot..

I see what you're saying - 12z runs will be interesting to say the least

[Jason M]

1 minute ago, john mac said:

Is it not more about the cold air undercutting from the north west. 528dam line just behind the front on the faxes. 

Fair point. Trouble is that its a PM airmass and it tends to be warmer lower down because of the sea track. Nothing is impossible in life but I think that chart is highly unlikely to verify come the day. If it was a being followed by a true Arctic blast maybe (still rare though). Again its only my opinion and hopefully ill be proved horribly wrong! An hour of heavy back edge snow might not be out of the question though even on lower ground.

[john mac]

Would love to be under it! Lol this is definetly not a done deal! 

[bluearmy]

By 6:30 pm we will have seen all of the ops ....safe to say that by 4 pm, there could be despair on here if we lose the Ukmo. I would expect the Ukmo to drift towards the ec solution but only a little. There is likely a middle ground area we will coverage on between the progressive ec and the slow Ukmo.....gfs will probably oscillate within an envelope ......I’m not expecting much from this initial spell snow wise as the nor’easter will e fairly short lived  affair as the ridge pushes in and the euro trough fails to sustain with enough intensity 

[Nick F]

2 minutes ago, Jason M said:

Fair point. Trouble is that its a PM airmass and it tends to be warmer lower down because of the sea track. Nothing is impossible in life but I think that chart is highly unlikely to verify come the day. If it was a being followed by a true Arctic blast maybe (still rare though). Again its only my opinion and hopefully ill be proved horribly wrong! An hour of heavy back edge snow might not be out of the question though even on lower ground.

Yep, generally rare to see frontal back edge snow in the south with a northwesterly polar flow undercutting, but an arctic northerly flow can produce back-edge snowfalls in the south, 25th Jan 2004 nationwide thundersnow event along a potent cold front moving south a good example. Be nice to experience here in the south back edge snow with a NWly undercutting for once though!

[DanDorsetUK]

14 minutes ago, Daniel Smith said:

Hard to tell but does that storm look a little North-West of where the GFS predicted it?

Just went on to the current radar it looks way out to me!

[Updated_Weather]

1 minute ago, Rapodo said:

Just went on to the current radar it looks way out to me!

By quite a few miles to say the least;) 12z runs crucial..

Exciting but nerve wrecking times!

[Met4Cast]

ICON is further East with the US low but further NE with the ridging so swings and roundabouts 

[Winter Hill]

23 minutes ago, Daniel Smith said:

Hard to tell but does that storm look a little North-West of where the GFS predicted it?

Good spot indeed.

hard to say, But if you look at Florida on the satellite image and then look at Florida on the chart, I would say it looks more West South West. 

Just my thought. 

Edited January 19, 2019 by Winter Hill
Typo

[DanDorsetUK]

1 minute ago, Winter Hill said:

Good spot indeed.

hard to say, But if you look at Florida on the satellite image and then look at Florida on the chart, I would say it looks more West Sourh West. 

Just my thought. 

Looking at the radar I think the storm may have actually slowed myself and it's not in the correct position. 

[Updated_Weather]

5 minutes ago, Winter Hill said:

Good spot indeed.

hard to say, But if you look at Florida on the satellite image and then look at Florida on the chart, I would say it looks more West Sourh West. 

Just my thought. 

Also I believe the storm is slightly weaker than Modelled? (1000mb to Modelled 1004mb)

Edited January 19, 2019 by Updated_Weather

[bluearmy]

Icon back closer to its 00z output