Model discussion - hunt for cold - Christmas countdown

[jellybaby1969]

36 minutes ago, Kasim Awan said:

It's far from over with the arpege, gem, jma, navgem going for a new solution of a more optimal period of trough disruption & therefore more cold / snow risk into Christmas. This appears to be a new solution. Interested to see how much support this has on gfs 06z ens.

I admire your positivity. Many people have been lead up the garden path with the boom posts and 20cm here n 30cm for there...yes you may post what you see however you need to open your eyes to all the data.....even the ones that don't agree to your cold bias

Edited December 22, 2021 by Polar Maritime
No need those kind of remarks.

[johncam]

Hi guys , think we need to get things in perspective,  just watching the news and the weather hasn't been kind to Malaysia,  on the whole the weather never devestate us in this way 

[Kasim Awan]

5 minutes ago, jellybaby1969 said:

I admire your positivity. However think you are now becoming a tad deluded chasing the cold and snow. Many people have been lead up the garden path with the boom posts and 20cm here n 30cm for there...yes you may post what you see however you need to open your eyes to all the data.....even the ones that don't agree to your cold bias

Calling other members deluded wont do yourself any favours.

Your sentence highlights why it's not a done deal yet. I mean for better synoptics, which itself does not neccessarily guarantee snow.

I'm saying it's too close to call which is reflected in most credible sources. The milder option is somewhat favoured though.

Edited December 22, 2021 by Kasim Awan

[Purga]

10 minutes ago, SqueakheartLW said:

For those of us who are downbeat about the 00z output only need to cast their minds back to Christmas 2000.

The forecast was for snow showers in Scotland and far N of England with rain and sleet for most of England and Wales.

What ended up happening?

The fronts ended up a lot further south in the end with only the south coast in the less cold air. The rest of the UK was cold and bright with scattered snow showers so you never know.

You need some of this

[supernova]

51 minutes ago, johnholmes said:

Not offended at all. I have had egg on my face too many times pre computer days and using computer models to take offence. All get it wrong at times. although I do find this latest forecast/model, confusion' shall I call it, as bad as any I have seen in a very long time. Just what the reason is I have no idea. As most on here know I use the 500 mb charts to try and get some idea of what may happen with the weather in the next 6-10 days, sometimes out to 14.

Taking a look this morning at them

ECMWF/GFS DAY 8-10 MEAN 500MB HEIGHT COMPARISON

WWW.METEO.PSU.EDU

Climate Prediction Center - 6-10 Day 500mb Outlook

WWW.CPC.NCEP.NOAA.GOV

They have slowly evolved over the past few days, The NOAA outputs are generally the more reliable and least prone to sudden changes , so looking at their outputs and the two main blocks west and east have been a feature for over a week. Beneath both of them the 500 mb flow has been mostly a westerly pattern. Maybe it is this configuration that has 'foxed' the models? It is not something I recall seeing before. As you can see on the NOAA chart it is still there. How the weather will play out over the next week or so, is still far from clear. Getting milder over the whole UK in the next 3-4 days looks pretty certain but beyond that then jh is going to find his place on the fence!

Not sure I worded my intended compliment as well as I could have done @johnholmes but my point was that no model beats experience and judgement, of which you remain a well-respected advocate.

Edited December 22, 2021 by supernova

[bluearmy]

27 minutes ago, chris55 said:

Could we get a Christmas miracle and remember the morning of the 22nd December as the biggest wobble in model history……

tell you later lol

It hasn’t just flipped overnight though. It flipped over 48/72 hours ..

 

21 minutes ago, northwestsnow said:

TBH the vortex is shredded .

We've just landed a piece pretty much exactly where we don't want it.

as is usually the case 

17 minutes ago, blizzard81 said:

I was banging on about patience last night but it now looks like we will need to dig into emergency supplies of it. Obviously a big flip on this morning's runs. Does anybody know if the modelling factors in solar activity? There are currently the most named sun spots on the solar disk since the peak of the last cycle. I really do think this has something to do with the huge flip for the worse with the models this morning. It would have to be something major to cause that huge flip. 

 

Some would certainly agree with you - I’m not sure how the nwp can take solar flares into account - someone will know 

2 minutes ago, Johnp said:

Can anyone give insight in to why our wedge has deflated like a burst balloon overnight?

It’s old age mate ….. 

[Updated_Weather]

3 minutes ago, Johnp said:

Can anyone give insight in to why our wedge has deflated like a burst balloon overnight?

Probably to do with the fact the Greenland block that was there - and now evaporated

[winterof79]

Its not so much the lack of snow over xmas thats annoying.

Its the dropping of the colder pattern

[bluearmy]

2 minutes ago, Updated_Weather said:

Probably to do with the fact the Greenland block that was there - and now evaporated

to put some meat on the bones here, the wedge extending se has detached from the greeny height rise which trends further west (yes we know jules) 

Edited December 22, 2021 by bluearmy

[Methuselah]

4 minutes ago, Johnp said:

Can anyone give insight in to why our wedge has deflated like a burst balloon overnight?

So that's it? I mightn't have any time for the usual 'it's the sun what done it' idea; but, missing balloon data? That's a different kettle of fish!

[blizzard81]

7 minutes ago, Johnp said:

Can anyone give insight in to why our wedge has deflated like a burst balloon overnight?

See my post above about solar activity. Has to be something major to cause that overnight flip. 

[nicknacknoo]

Disappointing though this chase has been, I think it was Mr. Murr who said that for proper Greenie highs you need to see those red heights in that region. We've never had that modelled so no surprise t hat it appears to have been easily eroded on nwp output. 

[Polar Maritime]

If folk can't post respectfully and friendly don't bother posting as it will go missing, Just like a few already have done..

Edited December 22, 2021 by Polar Maritime

[MKN]

9 minutes ago, Kasim Awan said:

Calling other members deluded wont do yourself any favours.

Your sentence highlights why it's not a done deal yet. I mean for better synoptics, which itself does not neccessarily guarantee snow.

I'm saying it's too close to call which is reflected in most credible sources. The milder option is somewhat favoured though.

Somewhat favoured?

Its around a 95% chance of being mild lol. Time to move on from this chase.

[Met4Cast]

If we really have to start pulling NAVGEM & other cannon fodder models out of the bag then it’s over!

[MattStoke]

In Kasim’s defence, if some model output still shows a colder outlook then it does remain a possibility, no matter how slim. Computer models calculate things using sound physics. They don’t just chuck out solutions at a guess.

Have to say though that the milder output looks far more likely this morning. One wouldn’t expect the lower verifying models to have called this correctly with little to no support  from the higher verifying models. It’s not impossible but it’s very unlikely, and weather forecasting is all about probabilities.

[Singularity]

The two lows saga also continued after all - they now interact more due to staying maybe 100 miles closer at the critical point.

That’s put the past 5 days at the top of my ‘most ridiculous modelling sagas’ list. I first started paying close attention in 2008 so that’s a major accolade

This does mean I can offer a few words or comfort to newer model-watchers: it’s not usually this bad!

This will need bearing in mind as the MJO & AAM cycle promote a similar overall sequence during the next few weeks to what we’ve seen this past fortnight: High builds up from Europe, then heads north or northeast, then either journeys west to become, or just gives way to, a Greenland High of some manner.

Stage one is evident in the model output for 7-10 days from now. Remains to be seen how much the surface flow is maritime versus continental at that point.

[BarometerCat]

Following same time frame  - 25th...

 

0z Yesterday (left) and today.    

 

Edited December 22, 2021 by B-C

[Earthshine]

7 minutes ago, blizzard81 said:

See my post above about solar activity. Has to be something major to cause that overnight flip. 

Well it was always fine margins whether it was cold or mild.  It didn't take much to push the models to converge on a particular outcome.  That's the thing with a chaotic system, very slight changes in the initialisation of these models can result in dramatic differences.  The cause of the flip was likely not anything major, it was just on a knife edge to begin with so didn't take much to push it to one outcome.

[Lukesluckybunch]

Just now, B-C said:

Following same time frame  - 25th...

 

0z Yesterday (left) and today.  Cold edging away again on this run. 

 

it doesnt get much worse then this,how has it dissapeared so quickly!

[camturbo]

Oh dear looks as if the mild will win out as things stand,could it flip to cold maybe possibly hopefully. Just goes to show how models flip and change and not rule anything out.

[winterof79]

Bang goes the theory that a True greenland high is the answer to all our prayers

[Kasim Awan]

6 minutes ago, MKN said:

Somewhat favoured?

Its around a 95% chance of being mild lol. Time to move on from this chase.

95% is ridiculously high given the volatility in output in the last 48 hours.

Remember it's an extremely finely balanced conjuncture. Only small changes in the atmospheric forces are needed to flip the balance in favour of the other outcome, which is why we're seeing huge swings as models attempt to handle these various forces. Each modelling handles them slightly differently which leads to an amplified knock on effect on UK surface conditions.

Importantly this means only rather insignificant changes in these forces could massively switch us back to a more optimal partern. 55/45 for milder outcome.

Edited December 22, 2021 by Kasim Awan

[Earthshine]

2 minutes ago, Earthshine said:

 

I'd say solar activity wasn't the cause of the flip it was just very fine margins to begin with

Edited December 22, 2021 by Earthshine

[IDO]

6 minutes ago, blizzard81 said:

See my post above about solar activity. Has to be something major to cause that overnight flip. 

I think with wedges, subtle changes in the energy distribution can have a knock on effect. We know in FI models tend to over do height rises and that dynamic here has meant the Greenland wedge is less distinct and the forcing of the trigger low under the block has failed, setting us on a new course:

Yesterday 06z> today>

It is endemic in modelling; micro-changes like this with subtle differences lead to exponential changes in some areas. The ens were always concerned with this possibility and FI remained under 4-days so it was always a possibility whilst there was model divergence.