[Model Output Discussion - Colder but how cold and for how long?]

25 minutes ago, Met4Cast said:

I think the hope of wedges remaining to the north with colder air across the UK beyond the 20th can be discounted now, this is a very strong signal from the EPS for a return to milder, wetter weather. 

The Canadian PV lobe being pulled towards Siberia (likely thanks to the recent warming) is the dominating signal and will override any potential blocking. 

Late January into early February however does still hold potential for a return to more blocked conditions with this next momentum surge. 

Before all of that though - A week of cold weather across the whole of the UK with the potential for snowfall just about anywhere. 

So the bitter irony and one we’ve seen before is the strat warming turns up and messes up the blocking by moving the PV .

It’s bit like heads you lose tails you lose ! 

[Model Output Discussion - Colder but how cold and for how long?]

From a low base a slight improvement in the ICON 06 hrs run . Less progressive so if it carried on likely a small extension to the cold .

 

[Model Output Discussion - Colder but how cold and for how long?]

Just now, Continental Climate said:

That's what has shocked me the most nick the rate of collapse. I thought 22nd/23rd but not this. The collapse is actually being brought forward. 18th/19th on some models. 3/4 day cold snap. 

Yes I think most thought we’d get to around that time .

Once the models latch onto a progressive signal it normally ends this way . The signal is even stronger today with as you said some ending the excitement by the 18/19 . I use that term with some sarcasm !

I’d prefer the GEM solution which keeps the rain and muck further away .

This is when the ECM now delivers the parting of the Red Sea and throws a morsel of hope to coldies ! 

Come on ECM you know it makes sense ! 

 

[Model Output Discussion - Colder but how cold and for how long?]

Just now, mountain shadow said:

Probably right by default though as it always ramps up the PV.

The biggest failure for me is the GWO/EAMT/MT teleconnections which really sucked me in to a proper snow cold spell of a couple of weeks or more.

 

Even the UKMO were duped .

As for the EC 46 I always thought it was tripe especially when forecasting colder conditions . 

That changes just as quickly as the rest of the NWP .

Just too much inherent chaos in the atmosphere . 

[Model Output Discussion - Colder but how cold and for how long?]

The models barring timing differences and the odd ensemble member which survives the carnage bring a rather depressing outlook towards next weekend .

The Canadian troughing ejects at rapid speed , flattens the pattern and very little energy heading se .

I don’t think anyone saw this rate of collapse . 

The ECM to come but it would be close to a miracle if that didn’t follow the other models .

 

[Model Output Discussion - Colder but how cold and for how long?]

Just catching up with the evening outputs which to be frank are underwhelming after Friday .

Just too much energy spilling east . There were some signs earlier that the energy would split with some heading se .

But the PV blob looks remorseless going by the day ten means .

The UKMO tries to split the energy but still finds an annoying shortwave to the nw .

It’s a bit frustrating in all honesty that the renewed upstream energy decides to turn up after downing a whole lot of steroids !

At least there’s a week of more interesting weather before the crapola hits the fan .

And although disappointing to see the block up sticks at the first sign of trouble some will at least see some snow and likely the odd surprise along the way .

I’d give it till tomorrow to see if we could just squeeze out less energy upstream .

It’s still just that far out in timeframe to hope for some changes .

 

[Model discussion highlights]

The GFS the most progressive solution .

The ECM makes changes upstream but still pushes too much energy eastwards .

Still time for that to change with more energy heading se .

The GFS is an outlier solution in the ne Pacific as it allows a ridge to move sw earlier than the others which helps to eject the Canadian troughing earlier and without any hang back so the whole thing barrels eastwards .

 

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5008188

[Model Output Discussion - Colder but how cold and for how long?]

The GFS the most progressive solution .

The ECM makes changes upstream but still pushes too much energy eastwards .

Still time for that to change with more energy heading se .

The GFS is an outlier solution in the ne Pacific as it allows a ridge to move sw earlier than the others which helps to eject the Canadian troughing earlier and without any hang back so the whole thing barrels eastwards .

 

[Model Output Discussion - Colder but how cold and for how long?]

The ECM, UKMO, GEM and ICON all disagree with the GFS in the ne Pacific at T96 hrs .

More about the impact of that area on the upstream pattern a bit later after my coffee !

[Model Output Discussion - Colder but how cold and for how long?]

2 minutes ago, TillyS said:

Totally agree Tom.

A cold week under an arctic flow, although nothing exceptional, before the Atlantic pushes back in c. next weekend without much in the way of boundary snow for most except Scotland and northern high ground.

Let’s see what the ECM brings.

 

Are you always this positive ! 

Clearly if the overriding signal was for a complete reset to gales and rain the GEM wouldn’t have made that overnight change .

I suspect this was an initial over reaction to the Canadian troughing ejecting.

Lets give it a few more runs .

 

[Model Output Discussion - Colder but how cold and for how long?]

A dramatic overnight change in the GEM which went mobile crazy last night .

Today the flow is more split with energy heading se .

The UKMO looks good upto day 6 and sort of drops the Ming vase at day 7 but still cold . Some energy moving se but you expected a better looking day 7 .

The GFS not as good as last nights 18 hrs run but it does look a bit suspect given the UKMO , GEM and ICON runs .

The uncertainty in the medium term is really how  the Canadian troughing ejects .

The whole lot moving east or whether some of that energy splits se.

Surely more changes to come there .

[Model Output Discussion - Colder but how cold and for how long?]

Indiana Jones And The Mystery Of The Disappearing Shortwave !

Very bizarre turn of events . 

This must be the first op run for days without that shortwave . 

[Model Output Discussion - Colder but how cold and for how long?]

1 minute ago, Bricriu said:

So maybe nothing  will be resolved till Sunday  evening as regards next week?

The northerly we can tick off .

The Atlantic low effecting the UK , still a question mark .

A few shallowish shortwaves effecting parts of the UK , I think that’s likely so some more prolonged snow for those lucky areas l

Any proper breakdown another question mark. Could be some parts stay in the cold for longer .

[Model Output Discussion - Colder but how cold and for how long?]

The wheels come off later on the ECM  as the Canadian troughing is ejected but then sort of runs out of puff .

The ECM is a bit like the GFS later which is somewhat bizarre given the divergence in the ne Pacific . 

And also bizarrely the ECM is a close match to the UKMO in that region but we can see two quite different outcomes downstream .

If we accept that the ECM GFS idea of ejecting that troughing is more likely we then now have to see whether we’ll see more of a split in energy and so could see some wedges of heights which can at least keep some parts still in the cold with continued snow chances .

The UKMO doesn’t have a great track record at day 7 but a combo of the Euros might be okay .

The GFS has that progressive bias .

If we are to see a bit of a reset then it can take a few runs to settle down.

Earlier there’s a lot going on , the brief but potent north to nw flow . Then the Atlantic low drama , a few other shortwaves thrown into the mix .

It’s hardly bridge night at the village hall ! So a lot to keep us interested .

 

[Model Output Discussion - Colder but how cold and for how long?]

Just now, MAF said:

YES YES YES.

all I want to know is the next 3-5 days, not might be in the next month. When will people acknowledge that past 3-5 days is totally unpredictable regardless of what a computer model is saying? I treat this as a Marmite thread. only because some people wax and wane over every output instead of just looking a few days in advance where the probability chances are massively reduced 

It depends on the pattern . Colder synoptics tend to be more volatile because they’re  not the default winter pattern .

And if we only discussed upto 5 days it would be pretty boring .

[Model discussion highlights]

Just now, Drifter said:

‘Scribble’ - great description for what GFS churned out in FI. 

I think I’d call it dog vomit ! 

 

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5007290

[Model Output Discussion - Colder but how cold and for how long?]

Just now, Drifter said:

‘Scribble’ - great description for what GFS churned out in FI. 

I think I’d call it dog vomit ! 

 

[Model Output Discussion - Colder but how cold and for how long?]

Some wild differences over the north east Pacific between the GFS and UKMO at day 7.

Because of this the GFS will shunt the Canadian troughing into the Atlantic.

The UKMO has a similar pattern over the ne Pacific to this mornings ECM op .

A lot of uncertainty in the outlook towards next weekend .

 

 

[Model Output Discussion - Colder but how cold and for how long?]

So the GFS 06 hrs run moves towards the Euros .

The interest now moves onto that upstream troughing .

The ECM has the more amplified set up . The direction of energy is se .

 

The GFS has the flatter troughing with the energy moving east .

 

The upstream troughing is now key moving forward in terms of extending the cold .

Anytime you get energy moving se good things can happen .

[Model Output Discussion - Colder but how cold and for how long?]

1 minute ago, Kasim Awan said:

Yes but with a slack flow the coverage of these features will be relatively poor, slack flow also means they will struggle to develop into larger features. December 2022 and November 2023 spring to mind. We need the low from Iceland & the one to our South to make better inroads for anything really significant otherwise a slack flow will just generate a lot of very dry cold weather with snow limited to a few coastal areas.

I think it’s best to save the obituaries till after the event .

Let’s just get the cold in with no dramas and go from there .

[Model Output Discussion - Colder but how cold and for how long?]

You’re going to have disturbances popping up with low heights over the UK .

I remember the last time we saw a slack cold flow and there was a lot of moaning that it would be dry and it turned out there were some surprises.

[Model Output Discussion - Colder but how cold and for how long?]

10 minutes ago, stewfox said:

Do you lean towards ECM or GFS or more runs needed 

The ECM is an upgrade this morning after last nights underwhelming effort .

Together with the UKMO and the GFS bias I think the Euros are more likely to have the correct trend .

 

 

[Model Output Discussion - Colder but how cold and for how long?]

The key is that the ECM sharpens up the upstream troughing at day 8 .

This means energy is moving se and will help to extend the cold .

[Model Output Discussion - Colder but how cold and for how long?]

A mixed start to the day with a blend of good and less good output .

The UKMO is the pick of the bunch with a cold extension likely post day 7 .

The NA models want to collapse the block quickly and become very messy.

[Model discussion highlights]

5 minutes ago, The Northern Ramper said:

Tamara has just casually thrown 1978 out there as the most likely set up, there has never been such a ramp.

That’s funny because the end of 1978 31st December I was flying back from Cyprus with family into Heathrow and there was loads of snow and the North Circular was bedlam .

And I’m flying back next week from Cyprus around the time of the Atlantic low drama .

Is this a sign ! 

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5005919