Model output discussion - proper cold spell inbound?

[Snowy L]

I think people forget how cold it can get in March. If you're saying first 2 weeks of March is too late then you should also be saying last 2 weeks of December is too early. The reality in both cases is a Scandinavian high will be bitterly cold.

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[Summer Sun]

GFS is definitely colder than GEM at D10 on the 12z

[markw2680]

18 minutes ago, FiftyShadesofSnow said:

Always said it was just a blip...gfs leading the way again

Yeah but look at the dates... getting pushed back as usual

[Polar Maritime]

Can we please use the banter thread to save clutering the thread up, Thanks.

[Thundery wintry showers]

2 minutes ago, Snowy L said:

I think people forget how cold it can get in March. If you're saying first 2 weeks of March is too late then you should also be saying last 2 weeks of December is too early. The reality in both cases is a Scandinavian high will be bitterly cold.

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It depends on the orientation of the Scandinavian high.  A south-easterly off the Balkans will typically be much colder in the last 2 weeks of December than in the first 2 weeks of March, and with the North Sea being near its coldest at this time of year, instability would be limited, and hence my suggestion of mainly dry and cloudy.  On the other hand, an east/north-easterly from northern Russia can still be very cold even into late March, as we saw in 2013.

[nick sussex]

At last some redemption after a downward spiral.

This evolution doesn't rely on an initial splitting of upstream energy but just the jet tracking ne so probably has a better chance of verifying.

The next few days will be a good test of the NWP in terms of pre SSW modelling versus post that.

[snowice]

33 minutes ago, ICE COLD said:

Ok I lied ? I'm not taking a break nice point to that high pressure and angle of attack . 

is it Tuesday 

[Weathizard]

Control going for the same theme but little worried about phasing across the top of the attempted ridging, quite knife edge this.

[Ice Day]

Out to 180 and the Control and Op are very much on the same page

Control  Op 

[Stuie]

I may be on my own here regarding Tuesday but I have my straws firmly clenched.

[Chris101]

I still can't help looking at that GFS run and thinking that is what i'd be happy to see with an mjo hanging in 7 for a bit (mlb) and then eventually getting to 8 (hlb), i just dont yet see a record breaking ssw smashing the vortex to pieces, i would like to think that is yet to really be seen. 

Edited February 11, 2018 by Chris101

[That ECM]

 Gfs mean with heights to the ne that drift to the nw. 

[Derecho]

Looking through the GEFS only 2 out of 21 runs show a disruption to the PV over Greenland/NE Canada up to T192. Quite a lot of runs do build high pressure and leave us in a rather cold easterly flow but generally mostly anticyclonic.

By T240 its still the same and many have a very organised PV around Greenland. High pressure over Scandi also a recurring theme.

However around T300 is when the output swings and from here a load of blocked charts start appearing. Not all of them have the UK under cold air however. It appears somewhere between T240 and T320 is the period where the SSW effects start filtering to the surface though it may be a bit more of a drawn out process then originally thought or the models may not have grasped it yet.

Alternatively some other factor could be hindering the potential for northern blocking but I remain to be convinced because of the magnitude of the SSW event taking place. It would require a very resilient PV indeed to withstand the SSW but the PV near Greenland has been dominant since 2013 (winter months) so who knows?

Chilly op run though.

Edited February 11, 2018 by Quicksilver1989

[Snowjokes92]

A quick one from me. Just running through the gfs 12z ensembles theres a few going back to the pattern dominant from the last 48 hrs with atlantic ridge blowing up the scandi high and strong easterly set up. A few other runs also build heights to east but take a different route and build over uk and into north east europe. We see the models drop scenarios like a hat, then revert back to old scenario. My opinion we will see the scandi block been the outcome, but i think it will occur few days later than original modelled. I also think the route of the block may occur how recent runs have been showing, where the high builds more over the uk, rather from atlantic. As for details i dont think its too much to worry yet anyway as output usually chops and changes and output swings this winter have well and truly been the form horse!

[EML Network]

Going through the various GFS runs and it's all getting very messy by next weekend, I really think we should ignore anything past then, a few examples showing just what a mess the output is, going to be some time before things firm up IMO. 

 

 

That's just a few cherry picked charts. 

There doesn't seem to be much support that follow the ECM route with HP to our South and the Jet stream running straight across the UK as if there's been no SSW what so ever, there's a few, this one for example, so that outcome can't be discounted. 

 

 

General consensus seems to be that High Pressure will come into play next weekend, it may stall out to our West it may dive south, it may pass through and to the East, or it may sit over the top of us. 

If I had to place a bet i'd go for the later, what happens beyond that...?? I don't think anyone can say with any degree of certainty, I was giving up hope completely of seeing a decent cold spell this winter that produces the goods, but after seeing today's set of ensembles I'm beginning to wonder if winter might just arrive in the nick of time.

 

[Frosty.]

Shirley the Ecm 12z will look better than this tonight!!..Anyway nice to see an improvement from the latest Gfs run!❄❄❄❄❄❄❄...it's still game on for cold / very cold late Feb.

Edited February 11, 2018 by Frosty.

[Ali1977]

GEFS back looking colder again, anyone fancy looking at a 1947 style period of weather look at P12 - can't post pics sorry.

Several have the cold easterly in by next weekend too.

 

Edited February 11, 2018 by Ali1977

[Daniel*]

3 hours ago, mountain shadow said:

The reality is the models have backed up a quick tropospheric response to provide decent favourable high latitude blocking for us, we therefore need to wait until early March.

This has aged well...

> 

model chaos but the cards are definitely there in our favour. 

[❄️❄️❄️❄️❄️❄️❄️❄️❄️]

P13, unlucky for some! 

[Snowjokes92]

Just cherry picked this lovely chart around 138 hrs from gefs. Theres a few of the runs that go towards a similar evolution. Hence the slght plit on the ensembles around day 5/6 this evolution was form horse in last 48 hours and is cropping up again? Anyone else noticed this in the ensembles. I think this route would be better for quicker and sustained blocking! @Steve Murr @Catacol what you guys think?

Edited February 11, 2018 by Snowjokes92

[Met4Cast]

That's some drop in the mean on the 12z compared to the 6z.

06z

12z

It's almost as if the models are struggling at the moment & Shannon Entropy is high.

[Derecho]

1 minute ago, Daniel Smith said:

That's some drop in the mean on the 12z compared to the 6z.

06z

12z

It's almost as if the models are struggling at the moment & Shannon Entropy is high.

Those are the 12z ensembles for saturday

[Frosty.]

I would settle for P12 on both the 6z / 12z!!

[Met4Cast]

1 minute ago, Quicksilver1989 said:

Those are the 12z ensembles for saturday

So they are.. I hate the new Wetter layout, I have absolutely no idea why they changed it.

[ptow]

1 hour ago, Snowy L said:

I think people forget how cold it can get in March. If you're saying first 2 weeks of March is too late then you should also be saying last 2 weeks of December is too early. The reality in both cases is a Scandinavian high will be bitterly cold.

.

No, it most likely won’t be. Most in mid winter are not bitterly cold let alone March. 

Of course it can happen but 9.9 times out of 10 it will feel cold but with temps well above freezing.