Model output discussion - The run up to Christmas

[Daniel*]

Diving low further east compared to ECM op centred in North Sea not Irish Sea.

[Kent Clipper]

An absolutely fascinating set up emerging. 

Its the perfect time of year to put faith in the UK's ability to see how effectively it can generate its own special cold pool next week. As we all know the longer the synoptic pattern holds up, the denser the air, the harder it becomes to shift.

Rather than focussing too much on 850Hpa's we need to keep an eye on the 925's and 950's. If you can get temps at this height close to 0c then you have every chance of bringing the snowline to the boundary layer if the precipitation is heavy enough and the lack of breeze prevents mixing. Easier still if pressure is low. eg. if its 0c at 950Hpa and you have a SLP of 980Hpa its closer than it would be if the SLP was say 1010 Hpa.

Living on the SE coast my chances of snowfall are probably less but convection is possibly enhanced due to proximity of the English Channel. Its a wait and see thing. I'm encouraged though to see that the chance of some snowy stuff is on offer during the course of the next week or so, including Christmas Eve and Christmas Day !

Loads to keep us occupied...what else can you do in tier 4 ? 

Wetterzentrale.de - Diagrams

WWW.WETTERZENTRALE.DE

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Forecasted New snow depth from GFS, 12Z

 

Edited December 22, 2020 by Kent Clipper

[Mr Frost]

Forget all the fancy number of snow parameters - when most of us see a bit of green or pink on the charts/models the chase is on! 

Few UKV precipitation snapshots looking ahead to the 27/12.

09:00:

 

12:00:

 

15:00:

 

Bank! 

[Allseasons-Si]

19 minutes ago, Zak M said:

Evening all, I just saw a snapshot of the UKV on Twitter - chance of sleet/snow for inland parts of EA on Christmas Eve if this was to come off:

Also, there's some pretty interesting feature on the day 10 ECM chart for eastern Europe - a sudden cold pool develops out of nowhere. Does this feature have a specific name?

   

Polar continental low!!!

[MATTWOLVES 3]

Little change with the extended ECM ens to day 14. We keep the cold theme going out to Jan 6th..around-3.5 to -4c uppers. Obviously could end up a degree or 2 below that...hopefully.

[iowpompeylee]

5 minutes ago, Portsmouth Sun said:

Really, half a cm?

Absolutely. It’s been a while 

[Allseasons-Si]

Ext EPS clusters show three clusters and are still looking good

[northwestsnow]

Dont read the met office contingency planning update.

Its a wash out ...

I thought it was from 2019 when I first read it.

I wonder if it was written prior to Glosea seeing  a SSW.. 

Edited December 22, 2020 by northwestsnow

[Northwest NI]

8 minutes ago, northwestsnow said:

Dont read the met office contingency planning update.

Its a wash out ...

I thought it was from 2019 when I first read it.

I would imagine that was written at the start of December?

[Dave Kightley]

8 minutes ago, northwestsnow said:

Dont read the met office contingency planning update.

Its a wash out ...

I thought it was from 2019 when I first read it.

Do you have a link? It has been a wash out for the South of late but that is what has happened not a plan

[Eastbourneguy]

Good evening everyone!

Exciting model watching times ahead!

One thing I would like to add when thinking about the 500 hPa Geopotential height, and forgive me if its already been discussed, but the height is taken from a reference level of 1000 hPa and not the surface. Adjustments to the actual thickness of the layer above the surface need to be made depending on the surface pressure pattern. 

This is an important to know when you're thinking about the general thickness/temperature of the layer, because if you're in a really low pressure pattern (quite often the case in the UK), the blues and purples can make it "look" like a colder/lower thickness than it really is in relation to the surface.

Here's an example: 

Which area has a lower thickness? A quick glance and you might think over the UK, but on closer inspection the pressure over the northern circle is far higher. If we look at the area of 520 thickness and take away 20 hPa to account for the ~ 1020 hPa SLP, the actual thickness between the surface and  500 hPa is around 500 dm (a very cold thickness very rarely seen in the UK). Where as over the UK, adjusting the blue 510 area up by 20 gives you 530. Still a cold thickness, but a marginal one at the surface, as you usually want around 528 or lower for snow at sea level. 

 

This theory can be confirmed by looking at the 500 hPa and 850 hPa temp charts.

 

The 500 hPa temp and height chart at the bottom is important here because even though the area over the UK has "lower heights", we know that's in reference to 1000 hPa and we can clearly see that the -35 C area at 500 hPa is far wider in our northern circle compared to over the UK.

 

Happy model watching peeps

 

 

 

 

Edited December 22, 2020 by Eastbourneguy

[Mike Poole]

7 minutes ago, northwestsnow said:

Dont read the met office contingency planning update.

Its a wash out ...

I thought it was from 2019 when I first read it.

I cannot believe this is out so early.  Maybe it relates to runs by their own models before GFS was shown to have predicted the upcoming spell better, much better.  They don’t look much at the GFS, but this for Jan-Mar:

Can I get 20/1 on the cold option then?  Is that how it works?  I’d put £1000 on tomorrow!

[Mapantz]

If you find that your post has disappeared, then it has ended up over here

Please stay on the topic of model discussion. 

[Scott Ingham]

26 minutes ago, Mr Frost said:

Forget all the fancy number of snow parameters - when most of us see a bit of green or pink on the charts/models the chase is on! 

Few UKV precipitation snapshots looking ahead to the 27/12.

09:00:

 

12:00:

 

15:00:

 

Bank! 

All in very modest 850 air in Scotland which shows the potential later in the week

[Updated_Weather]

2 minutes ago, Mike Poole said:

I cannot believe this is out so early.  Maybe it relates to runs by their own models before GFS was shown to have predicted the upcoming spell better, much better.  They don’t look much at the GFS, but this for Jan-Mar:

Can I get 20/1 on the cold option then?  Is that how it works?  I’d put £1000 on tomorrow!

How often has this actually been a decent indicator of what actually happens? Generally curious? 

[MATTWOLVES 3]

9 minutes ago, northwestsnow said:

Dont read the met office contingency planning update.

Its a wash out ...

I thought it was from 2019 when I first read it.

I wonder if it was written prior to Glosea seeing  a SSW.. 

Shocking mate...January 15% cold chance..55% near average..30% mild.

The 3 seasons on whole...5% cold...55% average...40% mild..

And good point...was this based on the Glosea run of a couple of weeks ago..if this is a recent run then its basic cancelling out any SSW chance,or not a significant one. Yet going on there monthly update,the outlook beyond mid Jan is again very uncertain.. 

[Man With Beard]

Still expecting the center of the low to be off the east coast, personally! I would expect any shifts to take place by T72, so still a couple of days to go for that.

Not seen a cut off low stuck over the UK since this one

uppers were a bit more favorable though

 

 

[Mike Poole]

Just now, Updated_Weather said:

How often has this actually been a decent indicator of what actually happens? Generally curious? 

It varies, it has been right when predicting mild, but maybe not beyond the probability that the weather will be mild in UK winter.  It has been awful at predicting cold, but that is less likely in UK so less data to form an opinion.  

One further point, this used (until last month) to be written with some science in it, but the new version is so dumbed down as to be not worth reading if you follow the weather, we’ve already seen the output from most of the models it is based on in some form, e.g. GloSea5 results were out about 11 Dec if only 3 month means, CFS we can see for free, and someone usually posts the ECM seasonal.  

[Tim Bland]

Do high res models such as UKV have more data on the variables required for snow than say the ECM? Ie does GFS & ECM have less data available to accurately calculate the likelihood of snow making it to ground level ? and for high res models that show it (ie Euro4) more accurately predict accumulation?  In a few days we will have a host of high res models to start looking at ! That will keep us from having to talk to our families in-between model runs

[bluearmy]

5 minutes ago, Man With Beard said:

Still expecting the center of the low to be off the east coast, personally! I would expect any shifts to take place by T72, so still a couple of days to go for that.

Not seen a cut off low stuck over the UK since this one

uppers were a bit more favorable though

 

 

Notice a sig difference of around 20mb in slp ! 

[Kasim Awan]

1 hour ago, Optimus Prime said:

On closer inspection we have this;

That looks very cold to me. Not far off early January 2010.

Looks like some special weather is on the way. Makes a change. 

A surface inversion will almost certainly develop inland from 2 days in that flow.

This will massively help with snow opportunities 29th/30th. An inversion essentially gives you as good snow parameters as the altitude of the summit of the inversion by removing the milder air between the surface and the summit. So it's like being 300m up if there was no inversion.

I do think it's a very fine margined set up - these have a potentially high impact yet low to moderate risk.

[Kasim Awan]

I think by Xmas day we will be in a position data wise to discuss potential snow outcomes 27th-29th.

Edited December 22, 2020 by Kasim Awan

[MATTWOLVES 3]

1 minute ago, Mike Poole said:

It varies, it has been right when predicting mild, but maybe not beyond the probability that the weather will be mild in UK winter.  It has been awful at predicting cold, but that is less likely in UK so less data to form an opinion.  

One further point, this used (until last month) to be written with some science in it, but the new version is so dumbed down as to be not worth reading if you follow the weather, we’ve already seen the output from most of the models it is based on in some form, e.g. GloSea5 results were out about 11 Dec if only 3 month means, CFS we can see for free, and someone usually posts the ECM seasonal.  

Mike the long range EC anomalies point to an above average temperature winter on the whole.. but this was last updated on the 5th of December.. im hoping the update for January is better..another thing worth mentioning is the fact some of these Long Rangers may have the Global Warming aspect programmed into them,like the met super computer. This could be another reason they go above average more often than not.

..

[Catacol]

42 minutes ago, jules216 said:

i have given up on trying to put my point across.Ever since november I have been mentioning here tíme and tíme again to look east as well not only NAO/AO "fetish" This winter has proven me right 100%.Appart from north of Scandinavia and Alps above 1000m there has Been no Snow in any major European Capital. EC 12Z run is perhaps the best example of blocking with very little cold- poor pattern to the east. 

It’s been a poor winter so far for Central Europe....but in response to more complaints about the Russian High - without it I don’t think we would be looking at such a meridional pattern now and the end of Atlantic influence, and in addition it is still incredibly early! It is only Dec 22....and if the split SSW happens (another product part driven by that Russian High) then probably cold will come to Europe. The U.K. will need some luck to ensure cold (some good stats on this over on the strat thread) but mainland Europe less so.

The meridional pattern has so far had you on the warm side. This won’t last....

[Updated_Weather]

6 minutes ago, Mike Poole said:

It varies, it has been right when predicting mild, but maybe not beyond the probability that the weather will be mild in UK winter.  It has been awful at predicting cold, but that is less likely in UK so less data to form an opinion.  

One further point, this used (until last month) to be written with some science in it, but the new version is so dumbed down as to be not worth reading if you follow the weather, we’ve already seen the output from most of the models it is based on in some form, e.g. GloSea5 results were out about 11 Dec if only 3 month means, CFS we can see for free, and someone usually posts the ECM seasonal.  

Noted. 
 

Thanks