Model Output Discussion - 18z 31/10/15 onwards

[Cloud 10]

GFS playing catch up with the magnitude of the Canadian ridging at day 6.

 

yesterday..  today..

[bluearmy]

As ed pointed out last night, gfs very top layers of the strat picking up some warming over Asia in two weeks. that remains on the subsequent runs but could, easily fail to make it below T300. It's not getting any stronger with each run so at the moment, odds against it becoming significant (though as we've seen over the past 48hours, odds against isn't always the least likely outcome)

[Polar Maritime]

The GFS 6z shows the Northerly for the 20th really digging South over the channel to France, Taking the Jet with it.. Pushing snow right down to the South coast, With some heavy falls model'd for the North all subject to change..

Edited November 14, 2015 by Polar Maritime

[phil nw.]

The GFS 6z shows the Northerly for the 20th really digging South over the channel to France, Taking the Jet with it.. Pushing snow right down to the South coast, With some heavy falls model'd for the North all subject to change..

Yes we are still on course for a much colder little spell from around the 20th.

Good agreement from the op runs for the cold established by next weekend,

 

 

Not the Greenland high of last evenings ECM and more amplified than the GFS in fact something in between-  a decent Atlantic ridge as shown by the UKMO  yesterday.

Slow movement west to east so the cold trough easing towards Scandiavia later with the Atlantic high moving towards the west of the UK.

 

In the shorter term though plenty of rain to worry about in some areas before the change.

 

those wriggling weather fronts bringing spells of heavy rain for the next few days.

[johnholmes]

Picking up on the last sentence from phil

UK Met warning for designated areas, part of their text

I am not 100% sure but this amount of rain must be a very rare event even for the areas mentioned? 250 mm is 10 INCHES of rain!

This flow is expected to bring a period of heavy and persistent rain, with 50-100 mm of rain falling in many areas. However, as much as 200 to 250 mm may fall across some of the most exposed high ground. 

Edited November 14, 2015 by johnholmes

[SMU]

Afternoon -

So things have settled a little today, the GFS has made the biggest movement in the last 24 hours - significantly increasing the amplitude of the wave over the states so that we get positive heights over greenland-

The ECM however has slightly toned down its extreme solution from yesterday with no cut off high - just the initial canadian blocking -

So either way the decent convergence still indicates a strong probability of cold weather spreading south in the latter stages of next week -

Post that there is still a chance of a significant block over greenland developing- Im pretty sure nearly all of our greenland highs have manifested out of vertical advection & ridging out of the atlantic, not out of a ridging canadian high ( at least not on its own )

However around day 9-11 there is a possibilty of x2 high pressures morphing into 1 as a deep polar low cuts across the pole -

If people can remember the second phase of cold - coming in mid dec 10 this came from this scenario

An atlantic high meeting a canadian high with a polar low -

If someone can care to post 14/15/16 of dec 10 then you will see what I mean ....

Cheers

S

Edited November 14, 2015 by Steve Murr

[Cloud 10]

Steve's charts in question from 2010.

 

[Frosty.]

Afternoon -

So things have settled a little today, the GFS has made the biggest movement in the last 24 hours - significantly increasing the amplitude of the wave over the states so that we get positive heights over greenland-

The ECM however has slightly toned down its extreme solution from yesterday with no cut off high - just the initial canadian blocking -

So either way the decent convergence still indicates a strong probability of cold weather spreading south in the latter stages of next week -

Post that there is still a chance of a significant block over greenland developing- Im pretty sure nearly all of our greenland highs have manifested out of vertical advection & ridging out of the atlantic, not out of a ridging canadian high ( at least not on its own )

However around day 9-11 there is a possibilty of x2 high pressures morphing into 1 as a deep polar low cuts across the pole -

If people can remember the second phase of cold - coming in mid dec 10 this came from this scenario

An atlantic high meeting a canadian high with a polar low -

If someone can care to post 14/15/16 of dec 10 then you will see what I mean ....

Cheers

S

Here is another version of the charts Steve requested. I'm pleased to see the chances of a cold spell from the north, our first cold weather of the season is increasing according to the models so far today and the latest met office update mentions it too which is what the majority of us on here were hoping for.

[Singularity]

I have my suspicions that for the south this potential for cold weather will amount to a few bright, chilly days following a dusting of snow that struggles to settle away from high ground, after which Atlantic air floods back in as the high topples.

 

Until see enough to suggest otherwise, my focus therefore turns to the wet and wild conditions of the coming week. What's happening today, with the severe conditions up north that last through Sunday, is just the opening act from what is typically our most troublesome weather pattern; a highly disturbed polar jet along a slow moving planetary wave. In other words, a broad 500 mb trough drifts slowly east while numerous disturbances run along the southern flank, bringing spells of wind and rain to the UK. Whereas from blocked patterns a severe weather event may affect one or two regions in a major way, the setup we have this week has the potential to bring multiple severe events that affect different parts of the UK each time.

 

The fact that we have an ex-hurricane adding to the moisture levels this weekend is really not helpful. Not only that but the Euro High holds on well enough to keep feeding some unusually warm, moisture-laden air up toward the UK periodically during the working week - the south may see temps rising into the mid-teens on one or two occasions, even in the middle of the night.

 

 

To summarise the main threats in the GFS 06z det. run as an example:

 

Sat-Sun

A biblical deluge across parts of North Wales and Cumbria with 150-250 mm possible, and generally very wet across the Northern Half of the UK while the south gets to dry out a bit on Sunday. Wind gusts reaching 40 mph across the central third on Sunday, perhaps as high as 50 mph where exposed.

 

A respite on Monday following a fairly short lived spell of rain and blustery winds overnight.

 

Tue

An energetic shortwave low rides along the polar jet, with some exceptionally warm air in it's warm sector. Again very wet for the northern half of the UK, but faster movement of the system should mean a repeat of the weekend is avoided. The south also sees a spell of heavy rain, but it's the winds that may prove to be the bigger problem here, perhaps gusting above 60 mph for a time even inland. The intensity remains uncertain to best to keep looking out for updates over the next 48 hours. With temperatures reaching 14-17*C widely across England and Wales, it may feel like another ex-hurricane despite being no such thing.

 

Wed

Another shortwave low that may or may not be as vigorous as Tuesday's system. The track is also uncertain, but the worst of the rain is being taken across the northern half of the UK (again!) by a number of models, which is very concerning. Wind gusts may reach between 30 and 70 mph depending on the intensity of the low and could affect anywhere from S. Scotland to the South Coast of England - so definitely one to wait for future updates on!

 

Thu-Sat

The risk of yet another active shortwave low, though there's little telling how deep it may be. This is the one that may feature cold air moving into Scotland on its northern flank, as the models are toying with it tracking right through England. Perhaps, then, the northern half will avoid the worst of the rain on this occasion - but could face a bit of snow instead, depending on how much cold air is pulled in and whether that happens before any rain has cleared away.

England and Wales are at risk of a large rain event as the low wraps in some more of that unusually warm, moist air. The worst of any strong winds are currently suggested to be across the southern half of the UK, but this could easily change given we're now looking up to a week ahead. The same goes for the rain - and I hope with everything I've got that it doesn't adjust further north and soak the areas that are getting hit hardest in the coming few days!

 

Sun

This is when it could turn notably cold across at least part of the UK, with the risk of some snow. It involves one final (hopefully...!) shortwave low that slides southeast through the day - or perhaps it will move differently - we can't be sure given uncertainties about how a ridge in the North Atlantic shapes up and how effectively higher pressure clears out of Europe. Another event to watch closely - this week is going to be busier than a beehive in a battle 

[Captain Shortwave]

The GFS shows around 1-2 inches UK wide with West Wales, Cumbria and south west Scotland seeing somewhere between 4-8 inches depending on elevation mostly. A pretty horrid week coming up.

 

GFS rainfall charts of course should be taken with a pinch of salt but fall within the guidelines of senior forecasters from what I have seen.

 

I guess if anything if we do get this Atlantic high it should start to dry things out a bit hopefully. But a long way to go to get to that juncture.

[Mucka]

I have my suspicions that for the south this potential for cold weather will amount to a few bright, chilly days following a dusting of snow that struggles to settle away from high ground, after which Atlantic air floods back in as the high topples.

 

 

 

 

Could well be, time will tell, but with a trough so close by there will always be the chance of disturbances in the Northerly flow bringing something a little better for some.

As always some might do well while others miss out but details for potential snowfall will be lacking for some days yet.

 

[Captain Shortwave]

Moving on with the 12z runs. A reasonable result from the GFS, enough to wet the appetite for the coming winter.

A rather cherry picked chart, but picked up to highlight a point going forward if we do see this cold snap develop.

 

Note the kink over Southern England, this is carried with 850s of around -6C along the eastern side of this shortwave feature. This would suggest an area of snow pushing south affected areas probably East of Bristol. Rain further west.

Don't take this seriously at this time frame, but this is the kind of thing you want to see if you want to avoid the classic wishbone northerly that we often see.

 

Haha Mucka spotted exactly the same thing...

 

 

Worth noting the UKMO is actually flatter than the GFS at day 6 on the 12z run.

Edited November 14, 2015 by Captain shortwave

[Mucka]

UKMO 144 looks like it would produce a possible channel low going forward

 

 

But thus far the output today has rather favoured a toppler so a cold snap rather than a cold spell.

Still GEM, ECM and JMA to come though plus there is plenty of time for downgrades or upgrades.

 

EDIT

 

GEM 144 possibly the best this evenings output from NH perspective.

 

Edited November 14, 2015 by Mucka

[radiohead]

12Z GEM also a lot less amplified compared to the 0Z run. (T138)

[Liam J]

Well I sure hope we're not just relying on the GEM to save the day.... UKMO shows a 24-36hr toppler then the pattern looks like it would flatten out with no build of heights into Greenland, GFS not quite as fast as the UKMO to flatten but does eventually, then into the depths of FI builds high pressure over the UK.... What will the ECM serve up later... 

 

 

 

 

 

[Ali1977]

Whilst it lookalike the weekend cold spell may only last a few days, further down route we are set up for reloads and possibly ones with better longevity. ECM will be interesting.

[Mucka]

Not the best of runs form GFS 12z for coldies but the bigger picture is quite interesting.

See below how there are repeated WAA episodes to our West and thus repeated attempts to build heights to our North.

 

 

If GFS is onto something then that would likely ensure we would at least get some decent PM air incursions heading into early Dec and with the chance of some more favourable MLB and HLB setting up for a more prolonged cold shot.

 

Edit Ali got there before me

Edited November 14, 2015 by Mucka

[Hocus Pocus]

Whilst it lookalike the weekend cold spell may only last a few days, further down route we are set up for reloads and possibly ones with better longevity. ECM will be interesting.

As per MetO updates. The fact is though this possible upcoming cold snap is already more amplified than previously modelled a few days ago so whose to say the next one down the line doesn't pave the way for a more longer lasting cold spell.

[Thunderbolt_]

It's looking like an exceptionally wet week is on the way, with bands of very heavy rain crossing the UK, pretty much every day between now and Friday. Temperatures will be variable as we bring mild sectors and cold sectors through the country. I wouldn't at all be surprised if we see some pretty widespread flooding by this time next week.

 

 

However, next weekend is starting to look very exciting for cold lovers, with the first cold northerly coming down from the Pole. We will most likely see the first widespread frost with hill snow, some of this even getting down to lower levels in the north and east. We're in for quite a lot of model watching this week, me thinks!

 

Edited November 14, 2015 by Thunderbolt_

[Mucka]

I have just run through GFS ensembles and at 144h it seems all possibilities are well represented from a non event toppler to something much more substantial.

Could go either way - a selection of which are below from non event to winter wonderland.

 

 

 

And of course lots of charts somewhere between the two. No doubt P15 is the holy grail though.

 

Looking at GFS 12z short ensembles for Northern England we can see the average 850 temp has just touched upon the magic -5c line for the first time so the over all trend is to firm up on a cold snap with longevity open to lengthening or shortening 

 

 

2m temps taking a nose dive

 

Edited November 14, 2015 by Mucka

[Mucka]

On the potential flooding.

 

Latest Euro4 paints a dismal picture for the NW over the next 24h

 

 

The threat gradually moves north over the proceeding 24h

[MR EXTREMES]

I word of caution the ecm is notorious for over egging heights,

but first to show a trend!.

but all models recently have shown similar ideas but I'd be inclined to suggest that a cold snap more likely than a spell.

But the eye candy was nice until today's runs gradual climb down has started.

Still not winter yet.

[Cloud 10]

Nasty  little LP in-bound at 72 hrs on the 12z ECM.

 

 

 

[MPG]

I word of caution the ecm is notorious for over egging heights,

but first to show a trend!.

but all models recently have shown similar ideas but I'd be inclined to suggest that a cold snap more likely than a spell.

But the eye candy was nice until today's runs gradual climb down has started.

Still not winter yet.

So a climb up yesterday now a climb down today? You always live up to your profile name! As you say winter not started but great trend in my book to see charts like this so early.

[Tim Bland]

Model performance stats show the facts... ECM is top dog so that is the most important model IMO!