Model output discussion 24/01/21

[sheikhy]

4 minutes ago, Tim Bland said:

Re ensembles...wouldn’t usually look at them for close range but this caught my eye for snow tomorrow at midday in the south...

Yup mentioned it in the regionals!!!gfs and gfs p further north and ukmo has the low ever slightly further north and deeper for tomorrow lunchtime compared to the 48 hour chart from yesterday

[Allseasons-Si]

2 minutes ago, feb1991blizzard said:

Look at the clustering -8c to -10c in London now, another uupgrade if you ask me.

Wetterzentrale.de - Diagrams

WWW.WETTERZENTRALE.DE

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Forecasted 850 hPa Temp. from GFS, 12Z

 

Yes even in the SE they are taking a nosedive.

the mean averaging out at -7.2c

[Neilsouth]

41 minutes ago, SLEETY said:

dont like this gfs run,messy and looks like quick breakdown,glad its the worst model in the verification stats.

They all look messy to me, little low pressures, not a clean north east wind, mostly -5 in the south. 

[Matt H]

The GEFS 12z ensemble mean is now diving down to around -7C by the 6th February with a significant (and growing) cluster of runs breaching -10C still as well. Looks great for the initial cold spell but the longevity and intensity of it is still to play for obviously. No need to panic yet IMO!

[MATTWOLVES 3]

I'm starting to get a feeling here that some are going to start playing this cold snap down before its given chance to get going on 1 rogue run!! And when it does come,some will be very quick to look for the end if it!! Met are on board this time folks its not the phantom one from 2019. 

Keep a cool head,and don't be surprised to see many more tweaks along the way...a little bit like your wedding vows...FOR BETTER OR WORSE.

Para looking good..

[IDO]

Looking at the d9 gefs and although the control has also flipped with the op, most of the members bringing in a colder few days, especially the further north you are:

That would suggest the op and control in the worst case scenarios and the 06z op was probably the best. So as you were, getting colder but how cold and for how long?

Edited January 29, 2021 by IDO

[Jeremy Shockey]

incredible ensemble mean on the GFS 12 z 

lots of opportunity for coldies after 5th Feb ( and before then too in the next 4 days )

any mild blip lasts about only 3 days

Edited January 29, 2021 by Jeremy Shockey

[Griff]

Parallel satisfactory at 204

[feb1991blizzard]

1 minute ago, IDO said:

Looking at the d9 gefs and although the control has also flipped with the op, most of the members bringing in a colder few days, especially the further north you are:

That would suggest the op and control in the worst case scenarios and the 06z op was probably the best. So as you were, getting colder but how cold and for how long?

One thing i am noticing on the GEFS 12z though, it is looking shorter lived than on previous suites, however it looks the type to me that it could be negatively orientated troughs coming up against bitter surface cold giving an only gradual but very snowy breakdown.

[Singularity]

 

Honestly, there's no reason to complain about the UKMO 12z. It has the stronger low to our east rather than west which means the very cold air would be funnelled in more during the following days.

GFS also places that strongest low further north than GFS(P) for example, which doesn't help.

That said - the single strongest model bias I know of is creating overly large, rounded troughs beneath highs in the Greenland-Iceland area.

Just look at this weekend with only weak high pressure there. We've gone from a balmy southwesterly flow most of the way up the UK to a genuinely cold weekend for all but the southwest corner, as the low has corrected to a flatter shape with secondary features splitting away east and as a result, no Iberian high sustenance.

So really, don't worry about models building broad troughs with Iberian ridges in the longer range. Only if that happens within the 5, maybe 6 day range is there legit reason to be concerned.

[nick sussex]

My Eurovision jury vote scores so far , overall .

6 points 

Thats basically my thoughts ! 

Public telephone vote 

7 points 

I suspect some IMBYISM which is natural as coldies are ruthless about their snow so where you live will determine your view so I’ve guesstimated an average. Put it this way if I was still living in Sussex you’d need the swear filter on red alert ! 

 

[Kirkcaldy Weather]

Just a post on the sea effect snow. From what I remember the thundersnow here at start of December had a 850 hpa / sea temperature difference of about 11C, looking at quite a few of the websites about sea effect snow conditions a temperature difference of 13C looks to be the key for proper snow bands, the current sea temp here  rounding that to 6C for easier calculation 

-5 850 hpa would be an 11 degree temperature difference 

-8 850 hpa (which is appearing as the current trend in the models) would be 14 degree difference 

-10 850 hpa which some runs are trying to get near the east coast would be a 16 degree difference 

I’ll leave the beast type 850s for now but you can probably do the working out for those should they arrive which remains a possibility. 

Lake/Ocean Effect Snow: Basic Ingredients

STREAM1.CMATC.CN

 

LAKE-EFFECT SNOW FORECASTING

WWW.THEWEATHERPREDICTION.COM

Obviously each area has different wind direction requirements for streamers here as straight an easterly as possible is perfect but I know @TomSE12 and @Paul Sherman are the go to for the subtle differences in the Thames streamers

[Singularity]

4 minutes ago, Griff said:

Parallel satisfactory at 204

Good impression of the GFS 06z at that point, funnily enough. 

[Man With Beard]

This is such a good mean chart for cold at D9 - however, there's a lot of flip-flopping at higher latitudes on the mean, which is fairly unusual. That said, it's not a usual set-up. 

Can I slip an extra thought in here? In 2013 and 2018, the SSWs led not just to one easterly, but repeated easterlies over the course of several weeks. 

[Allseasons-Si]

2 minutes ago, Griff said:

Parallel satisfactory at 204

Watch for that chunk of pv to break away to the NE as that separation splits the flow 

a good run this.

[Griff]

Just now, Singularity said:

Good impression of the GFS 06z at that point, funnily enough. 

I liked your recent post and have to agree, let's get to 180 before worrying about deep fi

[on the coast]

3 minutes ago, nick sussex said:

My Eurovision jury vote scores so far , overall .

6 points 

Thats basically my thoughts ! 

Public telephone vote 

7 points 

I suspect some IMBYISM which is natural as coldies are ruthless about their snow so where you live will determine your view so I’ve guesstimated an average. Put it this way if I was still living in Sussex you’d need the swear filter on red alert ! 

 

The UKMO tomorrow I feel will tell all. Its normally very good at 120.

[Jono E]

This could all go wrong, please please understand and learn the lessons of the past

[nick sussex]

5 minutes ago, on the coast said:

The UKMO tomorrow I feel will tell all. Its normally very good at 120.

Yes , once we get into that range the UKMO needs to be onside . The combo for easterlies is normally that and the ECM .

 

[Battleground Snow]

Most important development of the 12z runs is the Ukmo coming onboard at 120. Everything after this is up for grabs.

I like the control and p2

 

Edited January 29, 2021 by Battleground Snow

[The Northern Ramper]

17 minutes ago, MATTWOLVES said:

I'm starting to get a feeling here that some are going to start playing this cold snap down before its given chance to get going on 1 rogue run!! And when it does come,some will be very quick to look for the end if it!! Met are on board this time folks its not the phantom one from 2019. 

Keep a cool head,and don't be surprised to see many more tweaks along the way...a little bit like your wedding vows...FOR BETTER OR WORSE.

Para looking good..

And it seems to be some of the more seasoned posters getting hung up by a day 7 GFS.

[Man With Beard]

Had a look at ensembles D11. They have absolutely no idea what's going on. It really is like a bomb has gone off and different bits of the PV have been scattered randomly round the NH.

Still waiting for a seriously cold ensemble to pop up - I'm pretty sure a run with -20C uppers over the UK could be achieved from this pattern if everything falls correctly - it's extremely unlikely to happen in reality, but I'd just like to see it!  (it used to be like that chasing the +20C uppers in summer, now we see it every year)

[MJB]

Op 276h                                                        Control 276 h

[MJB]

240h Mean 

[bluearmy]

Genuinely amazed that posters can have any moans about the current output (apart from someone with a squirrel in the sw)

Even if it goes awry, it’s still brilliant model watching and half the reason the vast majority of you are here ! 
 

just enjoy it and ou never know, you may get to enjoy a few walks in the snow at some point in feb ....