Model output discussion - into the start of Winter

[nick sussex]

Major upstream drama !

A chasm between the big 3 now at day 6 . Until that gets settled then not much point worrying about what comes afterwards .

[Snipper]

Is this yet another year for so much hype but so little action?  Difficult to be positive from previous years experiences. 
 

Really hope my pessimism is proved to totally wrong. Got my skis ready. 

[Radiating Dendrite]

2 minutes ago, nick sussex said:

Major upstream drama !

A chasm between the big 3 now at day 6 . Until that gets settled then not much point worrying about what comes afterwards .

It's like Eastenders in here! BBC should just show zoom clips of people following the 12z runs!

My thoughts - ECM tends to over amplify and GFS usually always picks out the spoiler shortwave (mainly through luck than skill). Could be a mid Atlantic high, but something may scupper its sleigh ride to Greenland. 

[Skullzrulerz]

18 minutes ago, Tim Bland said:

ECM disagrees....

Unfortunately these "snow depth" especially at that range is quite unreliable but by no means it could be right 

Get to around 1-2 days before that said event and check them I don't think it's going to be anywhere near this 

[chris55]

9 minutes ago, Tim Bland said:

Looks good to me ...

Those milder 850s being forced north up into Scandi (previously modelled to sweep west over us) look to be staying out east allowing the U.K. cool pool to sustain at 168. Nothing spectacular but a good trend. 

[BlueHedgehog074]

Looking at various operational models at 72 hours for Friday, at the moment I think it’s fair to say the North-East of the UK is the favourite for the centre of the Low Pressure:

12Z GFS

12Z ECMWF

12Z UKMO

12Z GEM

 

12Z ICON

12Z NAVGEM

 

12Z ARPEGE

 

Northern-Eastern areas would seem like the target for the rain, sleet or snow. Since, though, it’s at 72 hours out, even at the range things can still change a bit. Shape of the Low Pressure not all the same on the models above. UKMO generally the most rounded with the Low. Plus, models, such as the ICON, has the Low Pressure more directly to the North of the Midlands in the middle of the UK, so does show that there is a bit of room for further alterations to the timing, shape and track of the Low Pressure on Friday. This affecting exactly where the coldest and most wintriest (especially over high ground) conditions end up.

For now, good support for areas to the North and East of the UK to see the longer spells of precipitation, again wintry over hills and probably to lower levels in heavier bursts. There is a possibility the Low Pressure through Friday could start winding back down South or South-West throughout the day carrying the wintry mix of precipitation down with it. 

Still going to be the case of looking out of windows to see whether anything falls, and if so, whether it will be wintry or not. Remember though, even if most areas, especially over low level ground, just see rain or sleet, it’s not 

 

Especially since more surprises through the Winter could easily crop up. A lot of time for those prospects. 

Edited December 1, 2020 by DiagonalRedLine

[ICE COLD]

Nice seasonal run from the ECM again .  No it’s not a major cold spell and blizzards but at least it’ll feel like winter in December for once .

[Kirkcaldy Weather]

@Steve Murr has taken over the GEM control run  

few others and also some of the GEFS still taking interest in getting blocking toward Greenland at some stage. Blocked in one way or another sums it up at the minute 

[nick sussex]

Yet more annoying shortwave activity upstream from the ECM at day 8 and 9. 

The one to the west needs to clear off se as the upstream pattern amplifies. Hopefully the day ten will stop all this nonsense and finally allow some deeper cold south .

[That ECM]

21 minutes ago, nick sussex said:

Major upstream drama !

A chasm between the big 3 now at day 6 . Until that gets settled then not much point worrying about what comes afterwards .

Nick. We are Going to run with ECM, would you let the other two know?

[Zak M]

12z ECM ends on a positive note with a northerly.

   

[Ali1977]

What a cracking chart for mid (ish) Dec, this would be a great place to be with the surface temp gradually getting colder in this set up I imagine!! 
 

[Mike Poole]

ECM finishing its innings on a fairly solid note, T240:

No route for Atlantic, and increasingly colder air over UK, and low pressure, snow chances increasing.  All good.

[chris55]

ECM 216

Slider incoming with a decently cold continental ‘pick up’ available (French airmass looks good to me).

In Summary, general synoptic pattern looks pretty decent for early winter  

[Allseasons-Si]

That's better at day ten...arctic rabbit='s arctic weather

Edited December 1, 2020 by Allseasons-si

[booferking]

To some up EC run rather cold start to finish. Trying to develop Greenland/Iceland heights all the time amen.

[nick sussex]

God it’s like the Alien Queen popping out these shortwaves like there’s no tomorrow ! 

The ECM day ten is littered with them although the chart is acceptable but jeez enough with these shortwaves .

[ICE COLD]

1 minute ago, booferking said:

To some up EC run rather cold start to finish. Trying to develop Greenland/Iceland heights all the time amen.

The pv is in bits too . Nice run from the EC again

[Catacol]

2 hours ago, Snow lover 2020 said:

What will wave 2 vortex do? 

Imagine a balloon pinched between your fingers. You end up with 2 smaller balloons. This is what warm air fired up into the polar vortex can do. The warm air acts to significantly reduce the temperature gradient in parts, and if 2 blasts of warm air are fired into the vortex from opposite sides of the globe then this acts to “pinch” the vortex just like the balloon between your fingers. We call this a wave 2 event. 

In situations where this happens the removal of strong westerly influence in sectors where the pinching occurs tends to encourage strong high latitude blocking and cold air spills out. However it is extremely difficult to be sure where the cold will end up. In Feb/March 2018 we hit the big jackpot though it was 2-4 weeks too late really to maximise cold impacts. Equally as the blocks form warm air is forced north....and so a split vortex event like this can produce very warm temperatures for some parts. Therefore it is a scenario laced with various scenarios....but in general the disruption to the vortex caused by the pinching increases cold outbreaks in lower latitudes.

Wave 1 events can also occur - warming on only one side of the vortex. Rather than pinch and split the vortex these events push it off its central axis and this can also promote cold outbreaks to favoured parts. Much depends on where the displaced vortex ends up. If Siberian led warming pushes it over Greenland/Canada it tends to be bad news for us (unless you like rain that is....)

What causes these warming wave attacks on the vortex? That’s a very complex subject. Not time to go into that here - go read up on it. Suffice to say that forecast patterns for the next couple of weeks are suggesting the possibility of a wave 2 attack. This doesn’t mean the vortex will automatically split (often the fingers don’t pinch the balloon hard enough to do more than force it a bit out of shape) but it is a start. Weaken it....hit it again in January and we stand a chance of a SSW inspired vortex split. 50% of Niña wQBO winters produce a SSW event big enough to cause serious grief for the vortex. Fingers crossed.

 

[Matt H]

1 hour ago, PolarWarsaw said:

I posted on Sunday that patterns quickly find a way to revert against us, our cold spells practically never in well over a decade of model watching come from having to sit, wait and patiently hope things fall into place for us (because they don't, a few days later a new pattern is always picked up and 99/100 it's an Atlantic set up) and although there is no consistent signal for the Atlantic to pick up strength, there's been small signs creeping in that after a few cooler days this weekend, we are heading away from a colder set up into the middle of next week. If that happens then I suspect that the positivity we've seen up to now will be replaced a more realistic vibe...this set up is firmly the lip stick on a pig scenario. 

We are very far down the line from anything remotely like a widespread, recognised cold spell with lowland snow. 

This aged like a fine wine. There’s plenty of potential for a cold spell at the moment even if nothing comes of the model output. I’ve seen far worse model output than this, particularly in recent Decembers.

[TSNWK]

And... even all those short waves the overriding pattern is positive for coldies.. usually the whole lot comes crashing down in heap of Atlantic gunk on the back of one shortwave that pops up completely unannounced ( most impolite ) currently we have short waves all over the place and pretty much from now until end of the run... yet still the overriding pattern is positive..

 

for once we are dealing with variation of theme cold wise....

[Allseasons-Si]

3 minutes ago, nick sussex said:

God it’s like the Alien Queen popping out these shortwaves like there’s no tomorrow ! 

The ECM day ten is littered with them although the chart is acceptable but jeez enough with these shortwaves .

Get the shortwaves in first Nick and then the cold and snow will follow

Jokes aside,there is so much uncertainty at days 5-6 between the models it's like watching dancing on ice one minute then watching strictly come prancing the next

let's see where this week takes us first before worrying about the following week and the next,and the next etc.

[tight isobar]

@nick sussex#shortwave dramas . They are paramount via ecm 12z .. but also easily overridden, if ya look through winter rose   tinted specs!   Anyway enough of this surface graduation temp “probability “??!. It makes my teeth itch!!. Upper level overhead and evolutionary head height.. is only deciphered at the point in time NOW .. we are a maritime island.. with vast SL differentiations.. and minimalist exactions play out... as they play out!!..  and have mass ramifications..short/mid term there are huge potentials for suprises.. this atm being a classic for evolution overide!.   But the bigger picture... paints pretty... well unless some ya look in the mirror ... jokes aside.. hemispheric gold...@going forward

Edited December 1, 2020 by tight isobar

[chris55]

9 minutes ago, nick sussex said:

God it’s like the Alien Queen popping out these shortwaves like there’s no tomorrow ! 

The ECM day ten is littered with them although the chart is acceptable but jeez enough with these shortwaves .

Is that from U.K. perspective or SW France?

[Man With Beard]

Nice to be in game for snow, at least!

However this is going to be a high stress period, with snow marginal at low levels, and probably localised. Most will miss out but some will get an early winter. Enjoy if it hits!