Model output discussion - the beast arrives

[Paul T]

GFS appears to have downgraded that 967mb low from yesterdays models!!

Oh Silly GFS and your overly progressive approach to low pressure to our South West...

 

[Tim Bland]

Wow not often you see 2m temps of -6c in the midlands at 3pm in March! 

Edited February 26, 2018 by Tim Bland

[CK1981]

4 minutes ago, Tim Bland said:

Wow not often you see 2m temps of -6c in the midlands at 3pm in March! 

They’re dewpoints.

[JamesL]

4 minutes ago, Tim Bland said:

Wow not often you see 2m temps of -6c in the midlands at 3pm in March! 

Dew points Tim 

[Badgers01]

5 minutes ago, Tim Bland said:

Wow not often you see 2m temps of -6c in the midlands at 3pm in March! 

thats because its the dew point and not temp

 

[Daniel*]

41 minutes ago, Zak94 said:

 excellent, a significant increase in pressure over Scandinavia at 93 hours, forcing the jet stream to take a more southerly track. This is far from over!

Maybe I’m seeing things I barely see any difference! I think a negligible observation, however I do less of west based -NAO and a more inflated round Greenland high probably negligible too...

[Badgers01]

Just now, Badgers01 said:

thats because its the dew point and not temp

 

definitely an echo in here !

 

[SLEETY]

So what would people forecast for thurs  be now,after looking at all the models.Even the met are not mentioning it in their video forecast this evening,seems it’s got everyone stumped lol

Edited February 26, 2018 by SLEETY

[nick sussex]

7 minutes ago, SLEETY said:

So what would people forecast for thurs Be now,after looking at all the models,even the met are not mentioning it in their video forecast this evening,seems it’s got everyone stumped lol

It’s like Kryptonite no one wants to touch it! 

For good reason as it’s still not sorted 3 days out.

[pages]

ok so lets look at bigger picture beyond Fridays low and where we trending.

I will use Icon to illustrate

18z-

 

12z-

trend is for vortex to be weaker displaced further south over Siberia. our low to go further south and weak surface heights developing to North east. over Pole we are seeing weak heights over Svalbard and each run the Aleutian ridge has a better attempt to gain latitude before it collapses. Now doesn't take great leap if trend continues to think that come day 7/8 that we may surface heights develop in Scandie at the same time the Aleutian ridge manages to get towards pole.

Models very slowly reacting to weaken Siberian vortex in response to second warming and also MJO going into phase 1?

 

[Derecho]

Right the 18z ensembles... time to update the swingometer...



I may have been to quick to make a snap call on the cold spell earlier (or at least my fears were too great) as it looks as though numbers have swung in favour of colder air remaining over England. Some parts of the midlands or wales may face quite a few days were maxima struggles to get above freezing. A weak and unstable set up such as this one however is subject to variation.

Some were difficult to call because the milder dewpoints were on the verge of creeping through most of England. Many ensemble members offer better disruption of the low leading to more widespread snowfalls down south and keeping the cold across England for longer. No outright majority here with the ensembles swinging a fair bit for saturday.

Now hopefully we can fight off more lows and keep the very cold surface air with the colder T850s moving back south....

Edited February 26, 2018 by Quicksilver1989

[Purga]

One of the posters on TWO has been in conference with UKMET (I think he may be involved with Highways / Transport) and says they are very bullish about the very cold and wintry theme continuing into next week, this despite the few challenges. He's based in Kent BTW.

[Snowbound]

1 hour ago, nick sussex said:

And the low drama continues!

A flatter low as Phil just mentioned, this is better at keeping the colder flow ahead of it.

I really wouldn’t look past T96 hrs at the moment because as we’ve seen the models are making a real soap opera over this low.

You also have to factor in what the later output is showing , will that stay the same as they get closer in or will more forcing cause a southwards adjustment .

 

If the low flattens to much or stays too far to the south that would put the mockers on a notable blizzard for Southern England. We don't want it too stay too far away !

[Donna3397]

Is storm Emma the same warm weather system due on Thursday/Friday or something completely different please

[nick sussex]

Regardless of what happens afterwards .

All the 18 hrs outputs so far have flattened the low so chances for snow at least at the start have increased.

You can see the forcing take place , the round shape swiftly turns into the more rugby ball shape within 12 hrs.

It’s still a difficult forecast and still liable to change until T48 hrs where we’ll get a better idea of the margin for error for areas in the highest risk versus those with less margin for error.

Very interesting to see how this develops.

 

[Jemma Croton]

I know this isn’t model specific but it is relevant to anyone dismaying about the events Thurs and Fri based on current output. 

I checked MetO for Swindon at 9pm or so and there was intermittent snow showing late Thurs and a bit of Fri. That’s now changed again to constant snow late Thurs, all of Fri and into Sat AM. 

To me this is a pretty clear indictation that, whatever the big 3 are spilling out, MOGREPS must be showing something else or a more favoured track of that low.

Hope that makes sense

 

[Jemma Croton]

13 minutes ago, DonnaThw said:

Is storm Emma the same warm weather system due on Thursday/Friday or something completely different please

Same but Met Portugal has named the storm hence confusion as we already had our E - Eleanor

[nick sussex]

1 minute ago, Jemma Croton said:

I know this isn’t model specific but it is relevant to anyone dismaying about the events Thurs and Fri based on current output. 

I checked MetO for Swindon at 9pm or so and there was intermittent snow showing late Thurs and a bit of Fri. That’s now changed again to constant snow late Thurs, all of Fri and into Sat AM. 

To me this is a pretty clear indictation that, whatever the big 3 are spilling out, MOGREPS must be showing something else or a more favoured track of that low.

Hope that makes sense

 

H Jemma it does make sense but be cautious when viewing those automated forecasts . 

As for the attention seeking low to the sw we still need more runs because it’s a complicated set up.

It’s always a difficult juggling act for the outputs to work out the forcing from the north and the north ne movement of the low from the south .

50 to 100 miles either way can make quite a difference in terms of ground conditions.

 

[SLEETY]

Surely the huge temperature difference between the bitterly cold air over the U.K. and the milder air associated with the low,is going to produce a mega blizzard somewhere ,hopefully the UK

At least the models FINALLY  agree that dense cold air is harder to push away than they  have been programmed to believe 

[Jemma Croton]

8 minutes ago, nick sussex said:

H Jemma it does make sense but be cautious when viewing those automated forecasts . 

As for the attention seeking low to the sw we still need more runs because it’s a complicated set up.

It’s always a difficult juggling act for the outputs to work out the forcing from the north and the north ne movement of the low from the south .

50 to 100 miles either way can make quite a difference in terms of ground conditions.

 

Always read them with a pinch of salt sweet. Just thought it might help some with the dismay xx

[essexweather]

Very quiet this morning

Both UKMO and GFS have the low further West on the 00Z runs. Slightly colder flow is maintained across much of the UK but for most of us we are stuck in no man's land.

Could be worse, although not what most of us want to see.

GFS:

 

UKMO:

Edited February 27, 2018 by essexweather

[Mike Poole]

Initial low still oval shaped on Friday on GFS at T84:

Cold holds until next week, uppers below 0C even in the south on Wednesday T192:

UKMO more rounded at T72:

 

Edited February 27, 2018 by Mike Poole

[MR EXTREMES]

As I feared the dreaded mixer is back.

Milder air into the south in 72hrs on the GFS 

Hate to say half the UK is into milder air after t72 ukmo and GFS swing back to quickly remove cold but northern England and Scotland remains cold for the rest of the runs.

Still here in balmy Portsmouth the snow is falling so it's still a bonus for down here disappointed to lose it quick.

Shame the second warming event came so late maybe February would have been a great wintry month.

Anyway I do now believe the fat lady is singing and for half of the uk at least it will turn milder or should I say average.

The only crumb of hope is that met office has the low elongated like some have said more easterly influence to start but this low must stay south of UK for it to benefit for longevity.

 

[SLEETY]

What a shambles,gfs has been utterly clueless in this position of the low pressure ,look where it is now compared to earlier runs.

 

Be surprised if they didn’t  give it completely overhaul ,

Like has been said before,probably only hit SW before retreating away S ,don’t think their be a big blizzard across the S now,maybe just SW,at most.

 

[CanadaAl]

21 minutes ago, MR EXTREMES said:

As I feared the dreaded mixer is back.

Milder air into the south in 72hrs on the GFS 

Hate to say half the UK is into milder air after t72 ukmo and GFS swing back to quickly remove cold but northern England and Scotland remains cold for the rest of the runs.

Still here in balmy Portsmouth the snow is falling so it's still a bonus for down here disappointed to lose it quick.

Shame the second warming event came so late maybe February would have been a great wintry month.

Anyway I do now believe the fat lady is singing and for half of the uk at least it will turn milder or should I say average.

The only crumb of hope is that met office has the low elongated like some have said more easterly influence to start but this low must stay south of UK for it to benefit for longevity.

 

To be honest I still think it's an upgrade to what we've been seeing in the last couple of days with the low being sent up across the uk and further north. We're starting to see the GFS model the cold pool and how it is slowing down the low and shallowing it. Don't get me wrong, an easterly trajectory would be far more favourable but the 0c isotherm only tracks inland briefly before being pushed south again on Saturday. Maybe i'm in denial but i don't think the fat lady has sung yet. I think late weds/thurs would be time to call it. I'm seeing echos of Jan 2013 happening. Low was modeled to send southerlies but with only 96 hours ahead, the negative tilt was picked up and there was a big snow event and the cold won (20 January 2013). I've added the models for comparison:

   Left: 0z, 16th January, Right 0z 20th January. 

Maybe not the best example but it shows how the models struggle with cold pools. 

Below is the diagram for the clusters for the 0z GFS (Cambridge). So far the op is on a milder track compared to the other members