Model output discussion 24/01/21

[sebastiaan1973]

Thanks Scandinavian High. Yep, that is a real Scandinavian High

[Man With Beard]

5 minutes ago, sebastiaan1973 said:

I see a lot of northern blocking. What a beast is member 10.

Model charts for Europe (Mean Sea Level Pressure) | ECMWF IFS HRES (10 days)

METEOLOGIX.COM

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ECMWF IFS HRES (10 days) - Current forecast valid for 02/07/2021, 01:00am of parameter "Mean Sea Level Pressure", model chart for map "Europe"

 

Yes sure, but not many of them engage really cold air within the 15 day period. The mean maximum for London between D11-D15 is 4C or 5C. Not bad, but not "beast".

[Stu_London]

Overall good trends for cold on this afternoon's suite. 

But, this aint no December 2010 or February 2018, where the models nail a pattern and we just count down the hours. 

There will be lots of twists and turns. A fair few ensembles stick fairly mild throughout. 

I feel resolving the events this weekend where there is lots of cross model conflict will go a long way to setting the pattern, but I wouldn't be brave enough to call where we will be in 10-12 days time.

Interestingly, the long term BBC video is massively ramping mild for 8-9 days time - guessing it must of been based on EC 0z, which I didn't see, but must have been not much cop.

 

 

 

 

[Johnp]

 

1 hour ago, MJB said:

I am Central Southern England and its gone from -2 to -4 

South Midlands, surely!

[Mike Poole]

ECM clusters from the 12z, T192-T240 and T264-T360:

As one might have expected given the mean, plenty of northern blocking there, first plot mostly -NAO (green border), second plot Scandi block (red border) significant - I think having looked at previous runs of these that Scandi blocking is the direction of travel.  But the second diagrams shows distinct options some better than others for UK, I like Clusters 2 and 1 in that order.  

[MJB]

1 minute ago, Stu_London said:

Overall good trends for cold on this afternoon's suite. 

But, this aint no December 2010 or February 2018, where the models nail a pattern and we just count down the hours. 

There will be lots of twists and turns. A fair few ensembles stick fairly mild throughout. 

I feel resolving the events this weekend where there is lots of cross model conflict will go a long way to setting the pattern, but I wouldn't be brave enough to call where we will be in 10-12 days time.

Interestingly, the long term BBC video is massively ramping mild for 8-9 days time - guessing it must of been based on EC 0z, which I didn't see, but must have been not much cop.

 

 

 

 

Yes I agree , it certainly isn't a '10 or '18 so expectations shouldn't go through the roof .

I noticed that with the Beeb , it's not out of the question they are playing catch up as you suggest.

[winterof79]

As stonking as some say the GEFS are it's not swaying the mean which is cool

[MJB]

2 minutes ago, Johnp said:

 

South Midlands, surely!

I think the Thames Valley / Chilterns can be both , but happy to be in either ( South Midlands / Central Southern England ) if that's where the snow is forecast lol 

[SqueakheartLW]

To show really how much even the next few days are still not nailed on you just have to take a look at how much variety there is just with the GFS 12z for Scunthorpe

First here is the ensemble spread

As can be seen a lot of scatter even in the near term but I have focused on key periods based on the average of the ensembles line

+72 hours - Saturday 30th January 12pm

At this range the difference between the mildest and coldest are as shown

Coldest

Mildest

At even this short term range there is some difference, mainly down to the placement of that low pressure to the south and where it crosses over the UK so the path of Saturday's low still isn't certain yet but for a colder outcome we really need it as far south as possible

+150 hours - Tuesday 2nd February 6pm

The next main period to focus on is the milder spell on average in the ensembles that peaks on Tuesday 2nd February at 6pm. Here is the difference between the coldest and mildest option at this range

Coldest

Mildest

The difference by this stage is much more noticeable. In the coldest option the low pressure out to the west clearly remained a weak feature and pushed across the UK to the south, a bit like the one due this Saturday so keeping us on the cold side of the jet stream and providing a potential snow event. The mildest scenario clearly blows this low up a lot more and sends it much further to the north so putting us on the milder side of the jet.

+234 hours - Saturday 6th February 6am

Our next main period of interest is at the colder dip of the average line further out where our next potential colder spell could be and the difference here is even more marked between the coldest and mildest options.

Coldest

Mildest

A big difference here with what is taking place and all is really down to how much of a Scandi block is there to the east of us. In the coldest option a pool of colder air sits to the east as well as a decent Scandi block and this is causing the low trying to push in from the west to stall and create a battleground with snow potential in the spine of the UK in particular. The mildest option has no such block to the east so there's nothing to stop the low just pushing in another milder sector across the UK

+318 hours - Tuesday 9th February 6pm

The next period I have picked out is where there is a big difference between the mildest and coldest options. Here they are

Coldest

Mildest

A stark difference here between the mildest and coldest options but what both do feature is anticyclonic conditions so maybe a hint here for dry weather in the 2nd week of February. What is crucial here is the positioning of this high pressure. In the coldest option it is more of a northern blocking feature feeding in some very cold air from the east. The mildest option is dragging very mild air up and around the top of the high pressure. No doubt a substantial difference in temperatures between each option.

+372/378 hours - Friday 12th February 12am/6am

The last two options I have featured are not from the exact same time of day but both are from the same day of the week and are simply the mildest and coldest options right near the end of the runs.

Coldest

Mildest

A big difference here between mildest and coldest but what both do have in common is northern blocking around Greenland. The main thing that separates them is the strength of the low pressure in the Atlantic. In the coldest option low pressure is rather weak so allowing the northern blocking to dominate the pattern in NW Europe so putting the UK into the deep freezer with a nice beast from the east setting up with even colder air to come. The mildest option has a much deeper low pressure out in the Atlantic bossing the pattern so despite the northern blocking the low pressure is forcing very mild air up over the UK so keeping the cold pool away over Scandinavia out of reach.

[Singularity]

Worth saving this, it's a weird work of art really - extremely anomalous warmth to the south of the complete opposite.

I'm not sure I've ever seen a stronger contrast in the Mediterranean-Europe area.

12z runs sure have been interesting but one has to wonder, having seen so much adjustment in the past 24 hours, might things adjust far enough further that the route changes yet again? Keeps me wary - but I guess that would at least make dry conditions more likely, which many areas could really do with.

If we do get an easterly via that wedge formation, though, then it will surely be GEM's biggest ever win.

[SqueakheartLW]

4 minutes ago, Singularity said:

Worth saving this, it's a weird work of art really - extremely anomalous warmth to the south of the complete opposite.

I'm not sure I've ever seen a stronger contrast in the Mediterranean-Europe area.

12z runs sure have been interesting but one has to wonder, having seen so much adjustment in the past 24 hours, might things adjust far enough further that the route changes yet again? Keeps me wary - but I guess that would at least make dry conditions more likely, which many areas could really do with.

If we do get an easterly via that wedge formation, though, then it will surely be GEM's biggest ever win.

Does that cold/mild boundary look like it is roughly following the M4?

[Singularity]

Also while we're in the downtime between runs - a gentle reminder that when there are easterly possibilities in the mix, the 850 hPa temps become a more complex guide with respect to snowfall potential as a whole.

If you want biting cold with long-distance 'streamers' then yes, feel free to seek the really low 850s of -10°C and below. Rarely easy pickings, mind!

If anything conducive to snow from disturbances floats your boat, then 850s as high as -2°C can be sufficient with a continental feed. The caveat being that you need those disturbances!

[Mike Poole]

ICON 18z T120 a little more amplified with more trough disruption than its 12z counterpart at T126:

[Chesil View]

8 minutes ago, Singularity said:

Also while we're in the downtime between runs - a gentle reminder that when there are easterly possibilities in the mix, the 850 hPa temps become a more complex guide with respect to snowfall potential as a whole.

If you want biting cold with long-distance 'streamers' then yes, feel free to seek the really low 850s of -10°C and below. Rarely easy pickings, mind!

If anything conducive to snow from disturbances floats your boat, then 850s as high as -2°C can be sufficient with a continental feed. The caveat being that you need those disturbances!

With regard to your last Paragraph James. I've been telling them this for years.  Viva Feb 78.

[sheikhy]

Today was nearly 10 degrees in leicester!!to even think that we could see significant snow in 2 days time is quite something!!!i think it will push further south in the next few runs

[sheikhy]

Keep me up to date my peeps!!just watchin footy right now!!!doing alright in fantasy football

[TallPaul]

2 hours ago, Kentspur said:

Is ECM out to wind us up in the SE corner or what

Hey K, count your lucky stars!.... just call it a minor blip...here (so far this winter) on the far south coast it's been one continuous blip! Call it Karma i say...our winter will end with 'the mother of all channel lows'...(one hopes!) ❄❄

[Tim Bland]

Icon looks like a sleet fest when you compare falling snow Vs accumulating. Wouldn’t take much to tip it the right way though obviously. Come on GFS .please match the ECM 

[Trom]

1 hour ago, Noob said:

Thanks for the replay Paul, so if thats the case how come models can show complete opposites at the same time frame ? Is there some human input involved or more a case of models see outcomes differently ? 

Each of the models is a set of fluid dynamics algorithms.  No two models are the same algorithm.  The major differences can be explained by:

1. Different starting data (the data is not perfect)

2. The set of algorithms

3. The resolution of the model (essentially they divide the globe into boxes, with each box impact the boxes next to it and so on).  More resolution = smaller boxes.

Due to the issues with incomplete and sometimes errant starting data the models also run ensembles.  These tweak the initial starting data to see what impact it has on the model over its run.

Hope this helps

[sheikhy]

1 minute ago, Tim Bland said:

Icon looks like a sleet fest when you compare falling snow Vs accumulating. Wouldn’t take much to tip it the right way though obviously. Come on GFS .please match the ECM 

Should know about now which way its goin for saturday on 18z!!if the low is further north in the atlantic for friday then its game on!!if its further south on friday then probably be further south compares to 12z come saturday!

[Tim Bland]

Goes for the north midlands but very marginal so mainly Pennines 

[sheikhy]

Just now, Tim Bland said:

Goes for the north midlands but very marginal so mainly Pennines 

Looks pretty good to be honest!!!midlands northern england!!more ecm than icon!!!we in the game buddy!!

[Mike Poole]

GFS T78, and channel low, but not cold enough in the areas that matter:

Still, wasn’t expecting much from this, it is the appetiser before the starter which happens in about 10 days, yes!  

[I remember Atlantic 252]

2 minutes ago, sheikhy said:

Looks pretty good to be honest!!!midlands northern england!!more ecm than icon!!!we in the game buddy!!

need a southward shift next few runs, it's too far north

[Griff]

Cue the discord...