Model Output Discussion - Christmas and New Year

[stewfox]

2 hours ago, Eskimo said:

Just to prove a point here and I think it's important in this thread so people can interpret the charts a little better

Back in 2010, 4 days before the 'event', the GFS was modelling no snow for southern areas and a band of snow for north eastern areas.

What actually happened, just 96 hours later, was little snow for north eastern areas and a band of snow crossing south eastern areas that dumped around 4-8". 

Things change quite rapidly. 

20 miles north of oxford Dec 18th 2010 as per above thanks to GFS alteration

[The Enforcer]

10 minutes ago, Mike Poole said:

I don’t know what it is with the M4!  On GFS I’m sure it is just a row of grid points...but on 10/12/17 it was absolutely the snow/rain divider, fortunately I was on the right side and got 5 inches of snow, but 10 miles south....just rain.  

If ever there was an example of even hi-res model uncertainty this was it. I think the best I got was 50% support from the hi-res suite. Only Arome supported snow all the way until T+0 when it switched to rain, even though others had moved the other way by then. It turned out to be a rain to snow event, so the other big learning point was in spite of hours of rain and saturated ground, the intensity was sufficient to provide a covering that rivalled that from the March 2018 event that followed.

[DanDorsetUK]

For what it's worth my Met office App this past hour has knocked off 2oC for next Fridays max daytime temp for the South Coast Bournemouth area. It was showing 5oC this afternoon, now it's only showing 3oC. That's quite a swing to much colder daytime temps.

[Weathizard]

As fun as this run is, take it with a pinch of salt... the GFS is playing funny buggers at the moment flipping around like a fish out of water

Must be that missing balloon data  

[Ice Day]

Fantastic inter-run consistency from the GFS at 198 vs the 12z 

  

I always look for these spells when the models start struggling with the mid-term.  Tends to be a solid sign that unusual things are on the cusp.  Not scientific at all, just something I've noticed over the years.

[Tim Bland]

Should set the North Sea snow machine up ready to bring snow showers inland...

[Allseasons-Si]

Scandi high forming 192>,Humber streamer setting up shop there.

 

 

 

Edited December 26, 2020 by Allseasons-si

[Battleground Snow]

Awesome para chart, at just 174, so much potential there

 

 

[sheikhy]

And control going same way!!

[kumquat]

Wash streamer again. Interesting to see:

Edited December 26, 2020 by kumquat

[Tim Bland]

Great fun the 18z GFS. Look at that snow depth over the channel. 15cm in Calais...push that low north a bit and we are in serious snowbusiness  There’s no business like snow business bought myself a poor mans snow board ...

[Ice Day]

240 on the 18z - fabulous

198 on the GFS Para - superb

The new pattern is now being picked up by the GFS.  The Control looking decent enough at 138 as well!

[nick sussex]

6 minutes ago, Battleground Snow said:

Awesome para chart, at just 174, so much potential there

 

 

A bit like my potential diet which remains marooned at the potential stage for months ! Joking aside although the GFS seems to be churning out a different solution every 6 hours it still hasn’t managed to churn out any mild crud upto day ten. This is a good sign for coldies as the background signals refuse to be pushed around by the GFS on the Christmas Sherry ! 

[kumquat]

Icy cold in the col:

[The Enforcer]

16 minutes ago, stewfox said:

20 miles north of oxford Dec 18th 2010 as per above thanks to GFS alteration

Probably the second best snow-related example of short-range change in modelling at T+12, to the extent that Rob McElwee presenting the late evening forecast actually said not to take the graphic showing northern snow limit being M4 corridor literally and that the snowfall limit the following morning would be more like the M40 corridor.

[XtremeUKWeather]

Wonderful Mean 18z

[BLAST FROM THE PAST]

If the 18z doesn’t end with an astounding blocking chart....I’ll be darned...it’s great all the way

 

 FRTP

[iand61]

3 minutes ago, MATTWOLVES said:

Hi mate.

The highest daily total in an inhabited area was 173cm..68 inches the location was Huntingdon,Warren, Dartmouth on the 16th Feb 1929.

So far so good with the 18s..improvements.

 

Blooming hell, no matter what HMG said, that would close the schools

[Cheshire Freeze]

Best thing about this run is it starts to show upstream amplify once again in its latter stages

Important to see repeated amplification to keep us ticking over until the SSW (hopefully) has some major effects

Edited December 26, 2020 by CreweCold

[Scott Ingham]

1 minute ago, CreweCold said:

Best thing about this run is it starts to show upstream amplify once again in its latter stages

And we stay cold with snow oppprtunies by being the right side of the jet in the wane period.

Imagine if this played out in the lull before the next injection of cold!

Cold pooling right in the heart of winter!!!

[Kent Clipper]

After 10 days locked in the preceding pattern the UK will become an almost inpenetrable cold block.

Big snow event on this chart. By this stage all the talk and worry about 850's will be a distant memory. 

 

Edited December 26, 2020 by Kent Clipper

[Tim Bland]

5 minutes ago, CreweCold said:

Best thing about this run is it starts to show upstream amplify once again in its latter stages

Important to see repeated amplification to keep us ticking over until the SSW (hopefully) has some major effects

With the PV shunted well to the east repeating ridges are likely

 

[danthetan]

5 minutes ago, Scott Ingham said:

And we stay cold with snow oppprtunies by being the right side of the jet in the wane period.

Imagine if this played out in the lull before the next injection of cold!

Cold pooling right in the heart of winter!!!

It really is looking like rinse and repeat, can't remember charts like this since late 2000's. 

[kumquat]

A long way off but decent snow fields over Europe.

 

A nice pub run to have a post-Christmas beer to.

[Scott Ingham]

2 minutes ago, danthetan said:

It really is looking like rinse and repeat, can't remember charts like this since late 2000's. 

Its absolutely fascinating this year Dan! 

Its the fact its happening in early Jan.

Well get away with marginality a lot easier than say late february and March before we hopefully see a favourable ssw induce some even colder upper air.

Very interesting to monitor daily temperatures the longer it stays as it is