Model Output Discussion - Deeper into Autumn

[cold snap]

6 minutes ago, Ed Stone said:

Well, the GEFS 12Z temperature ensembles are not exactly world-beating. But, hey, the winter-weather rollout is only just beginning!

    

Very very meh.

Blocked but not in a notable way.

[Kirkcaldy Weather]

It's wayyyy wayyy too soon to be stressed over the fine details re what type and amount of precip or level of cold 850s those specifics will still be shuffling positions on each newer run. If you want to focus more on the GFS 12z any showers that did develop wouldn't be rain, actually would be wintry showers with sleet and bits of snow as the 528 dam circles around the country  

Other factors in snow forecasting play an equally important role like dewpoint which needs to be at zero or below for proper snowfall and 850hpa temps but you don't always need -8 850s though that normally gives higher confidence in any precip being of snow, -5 850s normally begin to turn precip wintry so sleet and snow mixing in too again thats what the GFS 12z has across the country  , then there's evaporative cooling 

'Another reason that evaporative cooling is a significant weather changer is that it can cause a cold rain to turn into wintery precipitation. Evaporative cooling can be enough to cause the ground surface temperature to drop below freezing which leads to ice on the ground and travel problems. For example, the temperature could be 34 F with a dewpoint of 10 F. When rain falls into this air, evaporative cooling will cause the dewpoint to increase and the temperature to decrease. After saturation, the new temperature will be below freezing. This can change precipitation type from rain to snow, sleet or freezing rain. Weather forecasters keep a close eye on the evaporative cooling potential when the temperature is initially just above freezing since the weather could change dramatically to icing conditions after evaporative cooling.' 

WX CHANGERS- EVAPORATIVE COOLING

WWW.THEWEATHERPREDICTION.COM

Many of the GEM ensembles are fantastic

 

[Liam Burge]

42 minutes ago, Eagle Eye said:

Definitely not a bad start to the crossover between Autumn and Winter. MJO phase 6-7, a faily good looking AAM, weak zonal wind. We've seen worse positions,in fact you could argue we haven't seen a better starting position for quite a few Winters as I don't think 2020/21 started like this. If we keep the up for a month or two and don't get decent cold, we'll have to have been really unlucky.

We've already got 1 possible setup and we aren't even in December yet. With the MJO phase 6/7 lag, WAA is pushed up towards Greenland and possibly flips us to a -NAO style pattern over us and some early season colder air.

It's very weird considering the time of year and the oceanic La Nina phase. Like I said, there are worse positions to be in. @MattH a few posts above tells the story a lot better than me, as I'm just an interested 15 year old and I'd advise listening to him this Winter.

You're only 15?? You're extremely knowledgeable and your posts always give me something new to learn about how our weather works!!

[Geordiesnow]

Despite the blocked output, we are a long way off from a cold snowy output in all reality, one of those where patience is a virtue because the main bulk of the PV is heading towards Asia with impressive negative anaomolies whilst Scandinavia and Europe will be dealing with scraps. Unless we see troughing dropping down from the Arctic towards Scandinavia or down the Norwegian sea via a northerly, there won't be any mention of snow in the outputs. Hopefully we can get the dry anticyclonic weather from this rather than the chilly NE'ly the models are showing. 

[Liam Burge]

36 minutes ago, cold snap said:

Very very meh.

Blocked but not in a notable way.

Literally just the start of winter...

[Lukesluckybunch]

i would suggest people take a look at the ECM mean its fantastic!

[cold snap]

34 minutes ago, cold snap said:

 

Cold update from Joe 

 

 

[MattH]

Noteworthy, despite the time frame...

[cheeky_monkey]

1 minute ago, cold snap said:

Cold update from Joe 

 

 

echo's my post earlier about an exceptionally cold start to December here in Canada

[ANYWEATHER]

It's certainly gain traction ,now, still caution needed but looking more and more likely that Winter weather will start when Winter begins.......December!

[bluearmy]

Let’s see where the 00z trend but if you’re looking for euro low heights and high n Atlantic heights in December then you should be content - there has been a marked shift on the 12z eps to drop euro heights by day 10. This won’t be reflected on cpc because it doesn’t use 12z eps data 

[Frosty.]

This is a pretty good ECMWF 12z ensemble mean for the start of the meteorological winter if you’re hoping for increasingly blocked and cold conditions to evolve?!…I’m officially interested!  

 

[northwestsnow]

Just now, bluearmy said:

Let’s see where the 00z trend but if you’re looking for euro low heights and high n Atlantic heights in December then you should be content - there has been a marked shift on the 12z eps to drop euro heights by day 10. This won’t be reflected on cpc because it doesn’t use 12z eps data 

Dickens December ?

️

Just now, jon snow said:

This is a pretty good ECMWF 12z ensemble mean for the start of the meteorological winter if you’re hoping for increasingly blocked and cold conditions to evolve?!…I’m officially interested!  

 

Excellent - temps should start to tumble as the long night draws in..

[TSNWK]

30 minutes ago, Lukesluckybunch said:

i would suggest people take a look at the ECM mean its fantastic!

This....

[Mike Poole]

ECM clusters show a marked shift to totally blocked, T192-T240:

And a shift to Greenland, Iceland area, especially 2 and 3, which we’ve seen on the GFS op amongst other output.

T264+:

Choice of big block over the pole and to our north, and atlantic ridge.  Take either tbh.

Massive upgrades all round on the 12z suite, following a bit of a wobble this morning.

 

Edited November 22, 2022 by Mike Poole

[Lukesluckybunch]

2 minutes ago, TSNWK said:

This....

good isnt it?

[BlueHedgehog074]

Feel it’s worth saying that what it does still show on is latest update, that the NOAA/CPC 8 to 14 day 500mb anomaly chart is showing signs of the Atlantic wanting to go for a snooze out West. A reasonable pressure rise in that area extending from Iceland and Eastwards through Scandinavia. The upper flow across the UK mostly turns to the North-West - rather slack. Should cause the hat and scarfs to start coming out of the wardrobes bringing a few shivers.

 

Climate Prediction Center - 8-14 Day 500mb Outlook

WWW.CPC.NCEP.NOAA.GOV

Edited November 22, 2022 by DiagonalRedLine

[geordiekev]

1 hour ago, That ECM said:

What a pleasant change this would make.

Didn't Storm Arwen start under similar conditions back end of last Nov? Rare for cut off lows to sink South over Scandi & could get interesting as it comes into reliable 

Edited November 22, 2022 by geordiekev

[Uncertainty]

A mean easterly on the eps at day 10

 

The trend today seems to be for the significant amplification to occur to our west behind next Tuesday’s low. But there are variations on the theme.

The ECM is fairly representative tonight, taking the trough down the N sea into Europe with strong high pressure building over the top to the NW.

 

The UKMO looks out of place with this now, surprise surprise.

The GEM is yuck, but as others have pointed out still follows the general pattern it’s still blocked, just the trough gets stuck over the U.K. 

 

The para sends the low through France

 

The point is, there are still a large spread of options for this time next week, even though the destination (blocking to the N and a euro trough) looks rather set.
 

It’s after day 10 though that things could get really interesting…

This morning’s EPS at day 12

Westerly mean flow

This evening’s EPS day 12

Easterly mean flow 

It really is rare to see, in the canonical stormiest time of year, as pronounced an -NAO as that, especially modelled 12 days away. Plenty that can go wrong of course, but this signal has been signposted for months. Should it occur, it will be a victory for the teleconnection tea leaf readers. Of which, I am glad to be a member.

Edited November 22, 2022 by Josh S

[Lukesluckybunch]

its going to be fun watching the 18z unfold,all this blocking forecast is somthing else

[stodge]

Evening all

Steps in the right direction (sounds like something musical) but baby steps and a lot of detail to be sorted.

Hints at blocking to both NE and NW and to be honest most would take either - or perhaps one followed by the other.

As a southerner, the idea of an LP over northern France struggling to make inroads against a frigid E'ly in December isn't without appeal - far more than a straight anticyclonic outlook but I accept that scenario doesn't work so well for those further north.

As others have said, it's unusual as it's often quite a mile or very mild start to December with the vortex and jet at full throttle and +NAO the order of the day.

The GFS OP fragments the vortex while the Parallel move s it further west over Canada allowing heights to rise over Scandinavia and NW Russia and extend the vital ridge west or southwest over NW Europe.

[Eagle Eye]

I'd you were to ask me to get you a late November chart this would not be it.

Very interesting setup going into Winter..

[Lukesluckybunch]

the good news is that the building blocks arenot too far away,between 168-192h being the likely transition period into a colder scenario..the ridge between the two lows is where it all starts with a push of height rises towards iceland,this then combining eventually with heights over scandi,,,to hopefullyproduce a cold or very cold source of air from the east or northeast..the ECM was showing this!

[Eagle Eye]

1 hour ago, Liam Burge said:

You're only 15?? You're extremely knowledgeable and your posts always give me something new to learn about how our weather works!!

Thank you, I've focused mainly on the weather learning for the past 2 years and in recent weeks have been forcing myself to read 1 high level document per week and then discuss it on here and hopefully it's starting to pay off as I'm pretty much the forecaster for my school so people will get very annoyed if I get something wrong .

[Anthony Burden]

1 hour ago, MattH said:

Noteworthy, despite the time frame...

Evening Matt,impressive mean without looking at control.