Model Output Discussion - Into 2024

[January Snowstorm]

The Easterly is almost upgrading by the hour. Latest jma full blown Scandi High

[Rob 79812010]

18 minutes ago, on the coast said:

Brave call saying it wont last six weeks. Freak event coming coming up.

 

81 was definitely not a 6 to 7 week frigid period. Where have you got that from??

[Lukesluckybunch]

18z mean appears to be going the same way beyond 200h..all good news

[Cambrian]

There has understandably been a lot of focus on the initial setting up and location of the high pressure and the extent of northwestward retrogression. The role of specific low pressure systems and the forcing of the lobes of the PV is as vital to the evolution though. 

The 15 day animation of the 12z ECM ensemble mean shows the spawning of a series of lows during the next week, from the eastern North America trough, a southward extension of the Canadian lobe of the PV. 

The first two contribute to the formation of a deep system to the south of Greenland around day 4, which helps pump up the heights for the high pressure over the UK and Ireland. 

The trough moves east with these developments by day 6, and elongates southwards into the Atlantic, squeezed around the western flank of the fully developed, strong high, 1040mb+ now centred just to the northeast of the UK. 

Around day 7-8 (180h) is a critical juncture, as the high pressure intensifies further and begins to move northwestward, and in tandem with the rise in heights up into Newfoundland, breaches the trough, sending the cut-off low southeast towards the Azores, looking to phase with low heights over Iberia, and also bumping the high into further northward migration. 

The low pressure at the base of the residual Greenland trough rides up and over the Atlantic ridge, then down into the Norwegian Sea by day 9,

sealing off any potential eastward movement of the high, and on into Scandinavia by day 10, 

reinforcing the base of the Siberian trough and aligning the PV southwestward towards Northern Europe by day 12, which by then has grown bitterly cold.

 

In this modelling of the evolution, these ripples of energy, provided by the Canadian lobe of the PV, taking form in North American cyclogenesis, sent up and over the ridge, serve to fortify the forcing of a formidably cold European pattern via the Siberian PV, in one of the most compelling runs of the ECM ensemble mean that we are ever likely to see. Awesome. 

Edited January 3 by Cambrian

[MATTWOLVES 3]

18z ens looking sweet. The cold theme continues...solid mean also

Woooohhhhhh...come on dance with me..blackhole anomolies yet again. Strong support growing stronger.

Edited January 3 by MATTWOLVES 3

[easton888]

I've not only told my wife, but shown her the direct comparison between '63 and next week. Sorry everyone. Long time lurker, love the forum, keep it up everyone, you make my days as a dad of 2 little girls a lot easier especially at winter time. I bow to each of your inputs, I confess I can only see colours. But how excited am I for the 15th.....cheers, Adam

[Hotspur62]

Well things have certainly gone up a notch or two from a cold perspective.Got one more deluge to get over tomorrow down here and then we should all start to dry out a bit!Certainly gets colder from Saturday but mainly dry(still a chance of some light snow in East/South East but depends on how north the high gets on Sunday /Monday but not going those details until Friday night/Saturday morning.In the meantime it will be very interesting watching over next few days and all eyes on 14/15 January which seems to be start of possible snow potential for a lot of the U.K.!

[Kasim Awan]

25 minutes ago, Kasim Awan said:

The first few flakes?

Sunday

Temperatures gradually reducing from supporting snow only >400m early on Sunday afternoon to scattered cooled pockets of ground level snow line due to surface cooling by late allowing some of the rogue flurries to fall as sleet / wet snow >50miles inland where showers interact with surface cold, where this cooling does not occur due to cloud etc rain/sleet more likely. Freezing levels around 500m with significant surface warming in the east initially leading to high wet bulb driven melting widely.

Sunday night looks to bring a tight NNE wind which may produce a Kent clipper which would either be full snow or marginal dependent on depth of surface cold modulated by uppers influencing freezing level and wind speed which affect surface dew point layer. Stronger winds are an issue here. Potential for something interesting if it coincides with a cold sector and lightish winds as seen on ICON again which drops off uppers quickly into Monday early hours. -7/-9 850hpa core required so only a 25/30% chance as per current modelling. Combined with evaporative cooling could allow temporary ground level snow lines near the coast Kent etc. Also depends on this NNE wind being retained on output. Localized 2-6cm possible under best case scenario.

Monday

On Monday soundings improve where a 400m asl freezing level is enough in low dew point surface air 20-30 miles inland North of Essex for nocturnal wet snow showers and accumulation at night depends on precipitation though with daytime mixed wet precipitation. Nearer sea the long wind fetch North of Essex likely to result in near coastal warm layers. Few spots perhaps seeing a dusting at night Midlands Pennines East Wales.

Note less precip in SE later Monday but also lower dew points so more likely to fall as snow near to coast Essex South so any rogue flurries will probably be a greater snow to rain ratio than further North.

Bar the potential Kent clipper and perhaps some more organised very light precip Sunday night this is really only the odd shower. These will occur *as long as 500mb heights are kept below 556hpa*. Even if nothing appears on high res.

My snow sense is a bit rusty for obvious reasons.

Kasim ❄

High resolution UKV confirms this ascertion for Monday with the presence of scattered convection beloe 10,000 feet resulting in showers falling as snow into surface cooled air.

A freezing level below 500m and surface cooled air will almost always result in snow. A stronger easterly wind could be an issue here as without a cold surface a 500m secondary freezing level would be marginal. Two more points are the mixed phase precip boundary inlandward depends on wind speed and flurries well inland are possible due to convective mechanisms.

[damianslaw]

13 minutes ago, Bricriu said:

I wonder what the coldest  uppers have ever been from a northerly.  

Coldest upper temps at least in England and Wales tend to arrive courtesy of long fetch easterly incursions i.e. below -15 uppers, Jan 87 and Feb 18 are evidence of this.

Northerlies I don't believe have delivered sub -15 uppers other than north half of Scotland but could be wrong. 

[Nick F]

Oh dear, the annual comparisons to 62/63 being uttered.

Got my tin hat ready in case it goes Pete Tong 

But not often you see such a strong +height anomaly over Greenland at T+300, as below on 12z EPS

Same time Europe in the freezer looking at T2m mean anomaly

NOAA CPC 8-14 day heights look similar 

 

 

[on the coast]

Just now, Nick F said:

Oh dear, the annual comparisons to 62/63 being uttered.

Got my tin hat ready in case it goes Pete Tong 

But not often you see such a strong +height anomaly over Greenland at T+300, as below on 12z EPS

Same time Europe in the freezer looking at T2m mean anomaly

NOAA CPC 8-14 day heights look similar 

 

 

Liking the the little ramp  Must admit it all is looking very good for our small Island.

[Wold Topper]

7 minutes ago, Cambrian said:

There has understandably been a lot of focus on the initial setting up and location of the high pressure and the extent of northwestward retrogression. The role of specific low pressure systems and the forcing of the lobes of the PV is as vital to the evolution though. 

The 15 day animation of the 12z ECM ensemble mean shows the spawning of a series of lows during the next week, from the eastern North America trough, a southward extension of the Canadian lobe of the PV. 

The first two contribute to the formation of a deep system to the south of Greenland around day 4, which helps pump up the heights for the high pressure over the UK and Ireland. 

The trough moves east with these developments by day 6, and elongates southwards into the Atlantic, squeezed around the western flank of the fully developed, strong high, 1040mb+ now centred just to the northeast of the UK. 

Around day 7-8 (180h) is a critical juncture, as the high pressure intensifies further and begins to move northwestward, and in tandem with the rise in heights up into Newfoundland, breaches the trough, sending the cut-off low southeast towards the Azores, looking to phase with low heights over Iberia, and also bumping the high into further northward migration. 

The low pressure at the base of the residual Greenland trough rides up and over the Atlantic ridge, then down into the Norwegian Sea by day 9,

sealing off any potential eastward movement of the high, and on into Scandinavia by day 10, 

reinforcing the base of the Siberian trough and aligning the PV southwestward towards Northern Europe by day 12, which by then has grown bitterly cold.

 

In this modelling of the evolution, these ripples of energy, provided by the Canadian lobe of the PV, taking form in North American cyclogenesis, sent up and over the ridge, serve to fortify the forcing of a formidably cold European pattern via the Siberian PV, in one of the most compelling runs of the ECM ensemble mean that we are ever likely to see. Awesome. 

Fantastic concise post, as always, thank you

[LightningLover]

27 minutes ago, Bricriu said:

I wonder what the coldest  uppers have ever been from a northerly.  

Coldest I'm aware of is this (-17c at 850hPa in Scotland as it arrived!)

Edited January 3 by LightningLover

[IanT]

7 minutes ago, Nick F said:

Oh dear, the annual comparisons to 62/63 being uttered.

…

 

Yep. The models seem to show us a 62/63-like period every year, typically at the Ingham Horizon (T+288). 

Not saying it won’t happen this time round - at some point it will - but we should all be mindful of the verification record for modelled events of this nature.

Edited January 3 by IanT

[Mike Poole]

The 18z was so close to a SSW as well towards the end, here T324, 1 m/s:

Reflecting the new signal observed in the 46.

[Lukesluckybunch]

The mean nowhere near as cold past day 10...hmm

[booferking]

3 minutes ago, LightningLover said:

Coldest I'm aware of is this:

I think it was -18 850s scotland seen the chart on this fourm years ago cant mind when tho.

[January Snowstorm]

Look at the control!! Have we ever seen that depth of cold in Eastern Europe! It looks like some could spill this way too!

[LightningLover]

1 minute ago, January Snowstorm said:

Look at the control!! Have we ever seen that depth of cold in Eastern Europe! It looks like some could spill this way too!

-32c uppers on far right!!

[feb1991blizzard]

4 minutes ago, Lukesluckybunch said:

The mean nowhere near as cold past day 10...hmm

It will be by the end, look out for -10c flatliners galore.

[The Enforcer]

GEFS18z P23 not reading the script:

and unfortunately it's not the only one. Plenty of time for better, though.

[Lukesluckybunch]

2 minutes ago, January Snowstorm said:

Look at the control!! Have we ever seen that depth of cold in Eastern Europe! It looks like some could spill this way too!

I would say it's extremely rare to see the whites..never seen it before in Europe don't think

[Bricriu]

1 minute ago, LightningLover said:

-32c uppers on far right!!

What temperature  would you get at the surface if that made it to  the South East of England without being modified? 

[January Snowstorm]

So the morning will obviously be a key timeframe to see can we continue the trends of today. We are on the cusp of something extraordinary but not there yet... if things were to come off as modeled there is no doubt it would match 2010 and most likely cause huge disruption...IF..

[Bricriu]

2 minutes ago, The Enforcer said:

GEFS18z P23 not reading the script:

and unfortunately it's not the only one. Plenty of time for better, though.

As long as we don't see more of these popping up in the days ahead