Model output discussion - Closing in on Christmas

[feb1991blizzard]

Here she comes!!!

 

 

 

Edited December 20, 2020 by feb1991blizzard

[Snowman.]

FI but a proper Greeny block has been set-up, very cold uppers rushing south quickly.

[Tim Bland]

7 minutes ago, feb1991blizzard said:

This is going to be a proper Greenland high though, note the frigid air flooding SW towards us in a minute.

It’s like the weather god is pointing a finger straight at us

Edited December 20, 2020 by Tim Bland

[Vikos]

GFS is again

 

Yet again, everything after lets say 168h is like guessing the lotto numbers. But at least, the chase for cold isn't getting boring at all...

 

At least EC seems a bit more stable

 

[SLEETY]

2 minutes ago, Snowman. said:

FI but a proper Greeny block has been set-up, very cold uppers rushing south quickly.

We can build a proper Snowman like you when these uppers arrive 

[Frosty.]

I don’t think there would be much tinkering required with the current output to obtain a BLOCKBUSTER cold spell for the u k in the not to distant future (heights sucked NW)!..even now (with the colder trend during the week ahead)..it’s light years better than the mild crap we have seen in recent Christmas periods!

Edited December 20, 2020 by Jon Snow

[Methuselah]

Is the Finger-of-Frost headed for the Azores? Shirley not!

    

[Valleyboy]

27 minutes ago, SLEETY said:

What are the Sea temperatures now compared to 50 years ago,its the obvious reason why the uppers aren't lower

Nothing changed that much.  The problem with northerlies is that they always get moderated so much by the large expanse of sea they cross.  I can go back 50 years and remember the same frustration.  That’s why I don’t rate northerlies.  Easterlies for me.  The only good northerly is one that becomes established for a longer period.  Thats when lower temps can lock in.

[SLEETY]

Uppers being underplayed IMO especially at the time-scale being shown.Everyone should at least see snow falling out of the sky at worse.

Edited December 20, 2020 by SLEETY

[TSNWK]

Really enjoyed that 06z over a tier4 coffee and bacon roll. Synoptic wise more than content to bank and with an reasonable and considered view think we have enough going to scrape out a couple more points on the 850s and thickness to put the vast majority of us in the running for what we really want....

now.. how do spend the next 5 hours to 12z....

 

 

[captaincroc]

14 minutes ago, Battleground Snow said:

For those worried about uppers at 180-240.. we have seen a drop of 2 degrees within 72 hours for Xmas eve.. not impossible for them to come down again at longer ranges, plus this is just one model op run. Let's wait to see what happens once we bring this into the 72-96 hour range with higher resolution short range models before we proclaim it will all be cold rain.

I was reading through the posts and about to reply the same thing but you have done it for me.  I remember quite a few spells that started off being modelled at -4/-5 uppers to then creep lower -6/-7 nearer the time...  If this gets locked in then i suspect the same.

[pdiddy]

Quite a range of options available for Zonal winds!

[cheshire snow]

8 minutes ago, captaincroc said:

I was reading through the posts and about to reply the same thing but you have done it for me.  I remember quite a few spells that started off being modelled at -4/-5 uppers to then creep lower -6/-7 nearer the time...  If this gets locked in then i suspect the same.

Also not forgetting snow fell to low levels a few weeks ago with -2 to -3  uppers seems to be some who think -10 uppers are required not the case.

C.S

[Downburst]

19 minutes ago, General Cluster said:

Is the Finger-of-Frost headed for the Azores? Shirley not!

    

It is and don’t call me Shirley

[Midlands Ice Age]

10 minutes ago, captaincroc said:

I was reading through the posts and about to reply the same thing but you have done it for me.  I remember quite a few spells that started off being modelled at -4/-5 uppers to then creep lower -6/-7 nearer the time...  If this gets locked in then i suspect the same.

As an oldie can I also agree.

Many times I remember the MetOffice having forecast rain 2 to 5 days in advance, then change to sleet or hill snow. only to end up as all snow inland.

It is the distance to travel over the open waters that have the most  impact.

These 'open waters' SST's are about 0.2C higher than they were 50 years ago.

The effect is small and not really the reason. Temperatures (2M) South of Svalbard have been raised this year (so far), That is being corrected as we speak.

MIA 

 

[iowpompeylee]

1 hour ago, Jeremy Shockey said:

GEFS 06 z ensemble mean Christmas Eve 850 s

I'm still pretty interested in the " reliable " timeframe of 102 hours.  That is a very good mean for Christmas Eve. 

Wintry showers and some snow likely for a few lucky locations if we get precipitation. 

This is what I’m interested in. Xmas eve/day. Very cold winds. If only we can pick up some precipitation! Game on, anything after that period can wait. Just trends we have to look for! 

[kold weather]

This is going to be a tough call, the set-up IS there for snow but the airmass coming down at the moment doesn't look especially cold.

However you may well have multiple lows/fronts circling round an area of reasonably cold uppers and lower thickness. If we get any situation where we pull the winds in from Europe around any LP circulation we stand a good chance of turning any front to snow, as we saw a few weeks ago. The airmass ias it stands is likely to be colder than it was a few weeks ago as well.

Nothing screams snowfest *yet*, but there is more enough there that a watchful eye is deserved

[captaincroc]

16 minutes ago, cheshire snow said:

Also not forgetting snow fell to low levels a few weeks ago with -2 to -3  uppers seems to be some who think -10 uppers are required not the case.

C.S

I know this may sound very unscientific but also the short days and long nights I think actually help in marginal circumstances. For example on my birthday a few years ago (10th Dec) snow was moving in from the SW, I was living in Crewe at the time and it was snowing but wet and was struggling to stick...then as the light start to fade about 4pm the temp must have dropped ever so slightly but it just pushed the temps below 0 and it just started to stick. Plus with lower sun etc snow melt is less.

[SLEETY]

Dec 81 had UPPERS similar to what's being forecast ahead and look what happened that month, repeated heavy snowfalls and severe FROSTS. 

[Matt H]

GEFS 06z ensemble mean is virtually flatlining at -5C all the way through after Christmas other than a brief uplift on Boxing Day. Hopefully as we draw closer to the potential northerly blast there will be further upgrades as well. The best news of all is that there’s nothing resembling endless zonality in the model output for the foreseeable future.

Edited December 20, 2020 by Frosty Winter

[johnholmes]

45 minutes ago, TSNWK said:

Really enjoyed that 06z over a tier4 coffee and bacon roll. Synoptic wise more than content to bank and with an reasonable and considered view think we have enough going to scrape out a couple more points on the 850s and thickness to put the vast majority of us in the running for what we really want....

now.. how do spend the next 5 hours to 12z....

 

 

How about go outside and have a walk, breezy here but dry so far, very enjoyable!

 

[Tim Bland]

5 minutes ago, Frosty Winter said:

GEFS 06z ensemble mean is virtually flatlining at -5C all the way through after Christmas other than a brief uplift on Boxing Day. Hopefully as we draw closer to the potential northerly blast there will be further upgrades as well. The best news of all is that there’s nothing resembling endless zonality in the model output for the foreseeable future.

Excellent aren’t they! Almost every single run near or below -5. And right clustering / confidence, which in itself is unusual ! See below for London in list form for 28th

[swfc]

Gfs control in deep fi is pretty good 850s wise and nhp.

[IW Met]

2 hours ago, Penicuikblizzard said:

I thought it was better having the cold strengthening in Siberia for a bitter NE wind to be unleashed in weeks to come

Yes but it all depends on the synoptic setup.
If the cold is too far east, it will most likely stay there. The ideal scenario is for a low to plunge deep into russia and sink south/southeast followed by high pressure settling to the north of it (east/northeast of UK). This is when we get the super deep cold. You can on occasion get a retrogressing high but these tend to be on the same latitude as the UK, so yes they can bring cold but that tends to be later in Jan or Feb when the continent/russia/siberia is at its coldest.

 

[Allseasons-Si]

That's an impressive gefs 06z mean.

I'll say no more