Model Output Discussion - cold spell to end Autumn

[Man With Beard]

34 minutes ago, Man With Beard said:

Certainly has trended that way. Just the hint of a height rise towards Scandi there.

But it always seems harder for the models to pick up on a pattern change than when the pattern is staying the same. I think we're fairly well at until T192 with the coldish theme, thereafter I think we'll need to wait to see if the PV really will build into Greenland at last.

no, I take that back, looking through the individual ECM ensembles for D10, it's quite westerly dominated. The more amplified cluster D11-D15 tonight will be in the minority for the first time in a while tonight.

But still generally cold until D8/D9, and snowy episodes around (although nothing like yesterday's ensemble run for snow on the 16th)

[bobbydog]

26 minutes ago, snowking said:

For the South-East contingent - the ECM Control has an almost identical secondary snowfall event via that channel low for Monday Morning (this stretches up into East Anglia too). In fact, by my counting 29 of the 51 members produce some significant snowfall across southern counties (primarily CS & SE England) from that secondary feature around Monday morning.

The EPS overall still hugely varying on the snowfall line for Sunday, but the consensus remains M4 - M62 for the heaviest falls.

i just cant see it (yet...) the mean is colder than the Op so there must be a good few very cold members (oo-errr...). i'm certainly not dismissing it out of hand (heavy snow for southernmost counties that is) but we need to see strong signals from the rest of the models as we get closer to the 'event'

obviously i'll be watching intently.... 

[Paul]

So yet again, one entirely off topic post turns into 10. Come on folks, help us out a bit here and keep it to the models. 

[nick sussex]

The time between GFS runs seems to be very long when you're desperate to find out whats going to happen with this slider low especially if you're in the higher risk area for snow.

In the mean time we don't have much new data apart from the more USA focused shorter term outputs.

Now these come with a caveat they're focused upstream but do include the jet track out of the ne USA towards southern Greenland.

So these are the respective changes from their last outputs. The NAM was included in the NOAA diagnostic short term discussions and between its 12hrs and 18hrs, it has slightly increased the amplitude upstream with a small sw correction in terms of jet track in towards the UK for the slider low.

This is supported by the change between the 9am and 3pm SREF which does similar, that's the short range ensemble forecast system.

PS I'm not making any predictions for the GFS 18hrs run! So don't shoot the messenger!

 

 

Edited December 7, 2017 by nick sussex

[Nick123]

1 minute ago, nick sussex said:

The time between GFS runs seems to be very long when you're desperate to find out whats going to happen with this slider low especially if you're in the higher risk area for snow.

In the mean time we don't have much new data apart from the more USA focused shorter term outputs.

Now these come with a caveat they're focused upstream but do include the jet track out of the ne USA towards southern Greenland.

So these are the respective changes from their last outputs. The NAM was included in the NOAA diagnostic short term discussions and between its 12hrs and 18hrs, it has slightly increased the amplitude upstream with a small sw correction in terms of jet track in towards the UK for the slider low.

This is supported by the change between the 9am and 3pm SREF which does similar, that's the short range ensemble forecast system.

 

 

So do you think that is why FI is showing a flip to zonal? It seems a dramatic shift 

[Met4Cast]

1 minute ago, Nick123 said:

So do you think that is why FI is showing a flip to zonal? It seems a dramatic shift 

I'm baffled how you came to that conclusion from what Nick posted

[Nick F]

Extended EPS mean does paint an increasingly mobile / zonal picture out to day 15, as the Euro trough de-amplifies and heights rise toward SW Europe as the trop PV over eastern N America expands east over NW Atlantic. The signal for height rises to the NE rather faint too. As I mentioned earlier this afternoon, the flattening of the +PNA ridge is creating deamplification of the H500 flow downstream and allowing low heights to spread east out of Canada and more jet energy to flow and de-amplify the flow across the N Atlantic.

This from the CPC prognostic discussion today:

Quote

THE 500-HPA FLOW PATTERN DURING THE 8-14 DAY PERIOD IS PREDICTED TO BE SIMILAR  
TO THAT OF THE 6-10 DAY PERIOD, THOUGH WITH CONSIDERABLE DEAMPLIFICATION. THIS  
SIGNALS AT LEAST A TEMPORARY BREAK IN THE HIGHLY AMPLIFIED FLOW PATTERN ACROSS  
NORTH AMERICA, BUT ONLY TIME WILL TELL IF THE HIGHLY AMPLIFIED FLOW PATTERN  
WILL BE RE-ESTABLISHED SHORTLY THEREAFTER. INSPECTION OF THE WEEK-2 SPAGHETTI  
CHARTS CONTINUES TO REVEAL MODERATE TO LARGE SPREAD OVER THE EASTERN PACIFIC  
AND WESTERN CONUS, AND LOW SPREAD OVER THE CENTRAL AND EASTERN CONUS. 

http://www.cpc.ncep.noaa.gov/products/predictions/610day/fxus06.html

However, the extend ens means are prone to change and the 12z GEFS mean indicates H500 mean ridging over Norwegian Sea and Svalbard, so there is still chance yet of this height rises to the NE scenario unfolding in the run up to Xmas.

Anyway, lets enjoy the cold and snow prospects on offer the next 4 days and hopefully, in the meantime, the medium-longer term outlook will improve from EC/EPS over next few days.

Edited December 7, 2017 by Nick F

[Nick123]

Just now, Danny* said:

I'm baffled how you came to that conclusion from what Nick posted

Sorry maybe I didn't understand. I have very limited knowledge of the models! 

[nick sussex]

2 minutes ago, Nick123 said:

So do you think that is why FI is showing a flip to zonal? It seems a dramatic shift

Eh! No those outputs only go upto T84 and T87 hrs. This is just regarding the slider low drama.

[Nick123]

1 minute ago, nick sussex said:

Eh! No those outputs only go upto T84 and T87 hrs. This is just regarding the slider low drama.

Thanks for the reply. I shouldn't comment on stuff I don't understand haha.

[karlos1983]

Who broke the GEM it’s stuck on 48 on meteociel 

[bobbydog]

5 minutes ago, Nick123 said:

So do you think that is why FI is showing a flip to zonal? It seems a dramatic shift 

obviously nick can answer this but i think we are seeing the pattern change to blocking on our side. according to members with better access to other models, we should be seeing the pacific ridge fade and heights building to our north-east/west. i believe this 'zonal' period should be brief and transitional and should be expected. then leading to better things....

edit- the other Nick came in and peed on my fireworks....

Edited December 7, 2017 by bobbydog

[Nick123]

Here's hoping! With regards to the slider low is it a case of we want it to go south because that is a better indicator of longer term cold? I live In Newcastle and would love to see some of the white stuff but I would prefer shorter term pain for longer term gain!

[Summer Sun]

4 minutes ago, karlos1983 said:

Who broke the GEM it’s stuck on 48 on meteociel 

Updated hours ago here http://www.wetterzentrale.de/en/topkarten.php?model=gem&lid=OP

[nick sussex]

2 minutes ago, Nick123 said:

Thanks for the reply. I shouldn't comment on stuff I don't understand haha.

Everyone here started off on the net as a likely beginner and trying to understand about this complicated weather in the UK. So you shouldn't feel worried about asking questions and theres lots of different threads and a learning area to help you along the way.

[I remember Atlantic 252]

2 minutes ago, Summer Sun said:

Updated hours ago here http://www.wetterzentrale.de/en/topkarten.php?model=gem&lid=OP

bloody 'ell SS looks good! shame cannon fodder model

[Johnp]

3 minutes ago, Summer Sun said:

Updated hours ago here http://www.wetterzentrale.de/en/topkarten.php?model=gem&lid=OP

That's yesterday's 12z isn't it?

[Summer Sun]

Just now, Johnp said:

That's yesterday's 12z isn't it?

Oops was looking at the 00z

As you were not updated yet

[CK1981]

17 minutes ago, nick sussex said:

The time between GFS runs seems to be very long when you're desperate to find out whats going to happen with this slider low especially if you're in the higher risk area for snow.

In the mean time we don't have much new data apart from the more USA focused shorter term outputs.

Now these come with a caveat they're focused upstream but do include the jet track out of the ne USA towards southern Greenland.

So these are the respective changes from their last outputs. The NAM was included in the NOAA diagnostic short term discussions and between its 12hrs and 18hrs, it has slightly increased the amplitude upstream with a small sw correction in terms of jet track in towards the UK for the slider low.

This is supported by the change between the 9am and 3pm SREF which does similar, that's the short range ensemble forecast system.

PS I'm not making any predictions for the GFS 18hrs run! So don't shoot the messenger!

 

 

We may see the low slide further to the south in future runs then?

[alexisj9]

3 minutes ago, Summer Sun said:

Updated hours ago here http://www.wetterzentrale.de/en/topkarten.php?model=gem&lid=OP

Gem is a gem. It has a slack flow slider on Sunday channel low on Monday. And then more sliders and doesn't let the Atlantic in although it does seem primed and ready to pounce.

[snowbob]

13 minutes ago, Nick123 said:

Thanks for the reply. I shouldn't comment on stuff I don't understand haha.

No you should, as long as it’s model related, that’s how you learn !

there are some amazing knowledgable members on here and most always take the time to show you where you have gone wrong.

great thread this,and good luck.

18z now is it south or north or the same is the biggest question right now

Edited December 7, 2017 by snowbob

[Daniel*]

We tend to see the ensembles and everything go mild when a pattern change could be on the cards, one with blocking to the north east is quite seismic change to what we’re seeing currently. As Tamara eloquently says it’s the signals that drives the models not the other way around it takes time to filter through, and these signals are certainly not indicative of a hindrance towards cold blocked patterns.

Edited December 7, 2017 by Daniel*

[nick sussex]

2 minutes ago, CK1981 said:

We may see the low slide further to the south in future runs then?

No comment!

You have to bear in mind those outputs are US focused, sometimes they do give a preview of the GFS 18hrs run in the early stages but not always.

The slider is very complicated and that's why the BBC are being vague because its a difficult forecast.

[CK1981]

Just now, nick sussex said:

No comment!

You have to bear in mind those outputs are US focused, sometimes they do give a preview of the GFS 18hrs run in the early stages but not always.

The slider is very complicated and that's why the BBC are being vague because its a difficult forecast.

Thanks for the insight, Nick. It’s really useful and makes this situation all the more interesting!

[bluearmy]

7 minutes ago, alexisj9 said:

Gem is a gem. It has a slack flow slider on Sunday channel low on Monday. And then more sliders and doesn't let the Atlantic in although it does seem primed and ready to pounce.

00z run