Model output discussion - into the start of Winter

[sheikhy]

Aaaand we spoke to sooon!!!!!!!scandi high fights back again!!

[swfc]

2 hours ago, northwestsnow said:

I have the patent on wedges makes sledges....

I'm almost as possessive over it as Ian Brown and the christmas pudding thing ...!!

Anyway, lovely GFS 6Zif you enjoy cold weather !!

Indeed you do NW. Its probably your greatest moment and profound comment ever on here!!!!

[Eskimo]

ICON almost back to what was modelled by GFS and ECM a few days ago. Low across Iberia, dragging up mild upper-air. Will feel chilly at the surface making it seasonal over the course of the run but offering no more than that. 


 

[SMU]

Icon with a correction West shows how having a low close off around biscay can be counter productive for cold as it ushers the mild air up from the south-

Although noted however is at 180 the atlantic is not going to get through as some sort of easterly is in the offering, all be it a mild one...

[Frosty.]

3 minutes ago, PerfectStorm said:

ICON almost back to what was modelled by GFS and ECM a few days ago. Low across Iberia, dragging up mild upper-air. Will feel chilly at the surface making it seasonal over the course of the run but offering no more than that. 


 

Hmmm there is some interest before that timeframe you know ( in terms of snow potential)?..or at least there was on the GEFS 6z...and no doubt there will be on the GEFS 12z too..once it’s allowed to arrive!

[Eskimo]

8 minutes ago, Jon Snow said:

Hmmm there is some interest before that timeframe you know ( in terms of snow potential)?..or at least there was on the GEFS 6z...and no doubt there will be on the GEFS 12z too..once it’s allowed to arrive!

Specifically referring to the ICON 12z run though. Uppers don't appear conducive of any snow away from higher ground,  unless any of us own the Tan Hill Inn then you may be happy with the ICON output. 

Edited November 28, 2020 by PerfectStorm

[Updated_Weather]

Genuine question where does ICON compare to the big three in verifying %?

[SMU]

1 minute ago, Updated_Weather said:

Genuine question where does ICON compare to the big three in verifying %?

Usually a fair chunk below - but occasionally finds the right route..

Looks pretty fair does its 12z - all be it the final location of the lows east or west creates a large variation in upper air profiles over the UK

[Updated_Weather]

Just now, Steve Murr said:

Usually a fair chunk below - but occasionally finds the right route..

Looks pretty fair does its 12z - all be it the final location of the lows east or west creates a large variation in upper air profiles over the UK

Thanks Steve!

Does this model have any issues or biases like GFS tends to have also? Do we think its finding the right pattern regarding the Scandi High?

[SMU]

3 minutes ago, Updated_Weather said:

Thanks Steve!

Does this model have any issues or biases like GFS tends to have also? Do we think its finding the right pattern regarding the Scandi High?

I dont think many people study it to much to know the bias ! I believe what it shows at 180 isnt going to be far away in terms of wind direction IE somewhere from the ENE but finer detail TBC

GFS to 102 > minimal change. Slightly more forward motion off the eastern seaboard may help nudge everything further east

Edited November 28, 2020 by Steve Murr

[BlueHedgehog074]

I’m hoping both the ICON and ECMWF are over doing the Westwards shift of the pattern. Rather have the trough drop Southwards/South-Eastwards through Eastern UK (or at worst directly over us), to minimise the risk of dragging up those milder 850 hPa temperatures from the South. Feels like a waste, too, when you get these milder 850 hPa temperatures wrapped around an Easterly flow through the UK. Something that can make you feel tempted to throw a bunch of rubber ducks out of the pram. 

Having said that, it’s going to take a few more runs until the actual track of that Low Pressure coming down from the North-West early next week becomes clear enough. It looks likely at least that High Pressure will be amplifying upstream, which in turn forcing the Atlantic troughing ahead of it to drop some of its low heights down towards us. That Russian and Scandinavian blocking putting some pressure on the Atlantic trough also, and help with it disrupting. This is certainly different from the typical Atlantic, dominated, Westerly pattern that raids our weather. Quite a lot for the cold weather fans to be interested in at the moment. Even if this upcoming period doesn’t deliver much wintry weather, there could always be better possibilities further into December and the rest of Winter. By then, the upper cold pooling to our North-West, North, and (hopefully) East should become more expansive and be easier to tap into for cold and snowy weather. 

Edited November 28, 2020 by DiagonalRedLine

[Eskimo]

Relatively cookie-cutter stuff from the GFS in terms of the low's placement. 


 

[SMU]

GFS 12z pretty much a carbon copy of the 06z, as is the UKMO a carbon copy of its 00z.

Cold air arriving from the NW throughout Friday- chances of rain turning to sleet & snow over high ground...

S

[Eskimo]

Could evolve into a good run this (famous last words). Southerly tracking jet allowing heights to build north and west towards Iceland. 

[fromey]

I know these are just Forecasts and can change but looking pretty decent-AO there

[Zak M]

The GFS parallel has gone a bit bonkers.

-8/-9c uppers reaching S England

   

And a lot of snow for lower levels of south and east England

   

Absolutely ridiculous run!

[Catacol]

4 hours ago, Steve Murr said:

 

Could you based on your explanation inform us how much the NH air mass has been modified upwards?

How much expanse of the Nh of say the -10c isotherm has shrunk V the climatic norm.?

The bottom line here is that there is likely to be 'some' modification in the airmasses however the larger reason that you seem to have glossed over isnt climate change but the simple fact that the vast majority of any cold upper air over Europe is mixed out by warm southerlies ahead of the low - neatly obvious in the chart below-

 

Model - not CC thread - but two responses here. Stratosphere temps have fallen with CC hence sharper vertical temperature gradient and winter vortex speeds at the upper end of average expectations on a more regular basis. Stronger vortex, with elements of downward propagation always likely, means the coldest air more likely to be locked up north in a +AO context. If the AO turns sharply negative then to some degree everything changes.... but with our NAO and AO signature often now sitting in positive territory it means that synoptically there is less cold, dense air around at 55N.

The second response would be with regard to ice. With the retreat of the ice pack, currently in the second lowest position ever, it means less cold air in the troposphere even in the dark winter months, and this is particularly strongly felt in our atlantic sector. Both atlantic and pacific appear to have large expanses of water these days. The debate will continue to rage over reasons for ice melt - but it would seem odd to suggest that less ice = same amount of cold air to draw upon. I think clearly this cant be the case.

Ultimately synoptics will trump background warming for many years yet - and maybe by 2050 we can put CC into reverse - but even observational reality of a fairly loose scientific nature leads many of us old timers (and as I just turned 50 I must fall into this bracket now) to conclude that cold air sources are more scarce than they were 30 years ago.

Meanwhile - somewhat more on topic we continue to ride out a fairly average and non-descript phase. No substantive Nina ridge, MJO still coming back into the more interesting and active phases for us, and the ramifications of a substantive pacific jet extension on the back of a sharp +EAMT gradually coming into play. Some excitement across the pond at the impacts of likely pacific wave breaking from this development creating an alaskan ridge and downstream trough with snow potential for the Eastern USA, in week 2. Lag impacts might begin to interest us shortly afterwards as wave breaking impacts from the momentum surge add some potential to northern blocking opportunities, and on top of this torque inspired event I continue to emphasis the long term benefits of an entrenched ScEuro ridge and a recurrent low pressure signal in the north pacific.

A slightly odd winter so far really. Nino style patterns in a definite Nina background state, and a very strong vortex slow to couple as a result. Which way will it swing? If the vortex overcomes tropospheric forcing and couples, then we may find that Nina background state getting long term primacy and a nasty product for cold lovers. However things don't quite smell that way to me. We may have missed our chance of early Nina cold...but I plumped for an SSW in mid Jan (maybe late Jan) and I'm not changing that opinion for now. Plenty of evidence that this may occur and then true chaos will result in the latter part of winter. Wave 2 forcing signal strengthening mid Dec. Impacts to grow mid Jan.

 

 

 

Edited November 28, 2020 by Catacol

[northwestsnow]

ukmo 144 ...

Hopefully riding over the top of the troughing.....

[Tim Bland]

I get the feeling that this could be the year that everything falls just right for a cold spell around Christmas...

[swfc]

Great nhp profile and synoptics in fi and still zero decent 850s on the gfs 12z

[Tim Bland]

Just now, swfc said:

Great nhp profile and synoptics in fi and still zero decent 850s on the gfs 12z

Yep. So frustrating isn’t it to see the pressure charts then click on the 850hpa ones with anticipation...only to see there’s nothing interesting I think we need to be patient....

[Methuselah]

I'm very much liking the long-term potential... warm air pushing into a cold NE flow, can be one heck of a snow machine. Patience!

    

[swfc]

1 minute ago, General Cluster said:

I'm very much liking the long-term potential... warm air pushing into a cold NE flow, can be one heck of a snow machine. Patience!

    

Yes GC, baby steps

[Scandinavian High.]

11 minutes ago, Tim Bland said:

I get the feeling that this could be the year that everything falls just right for a cold spell around Christmas...

After the year we have gone through what’s betting we have first proper  white Christmas in a while

Edited November 28, 2020 by abbie123

[SMU]

4 runs of the GFS with no atlantic in FI - indeed what a signal-

Also the mean beginning to follow suit!