Model Output Discussion 5/12/2012 18Z onwards - the one after THAT ECM

[Paul T]

I think a full blown, dry and straight easterly is very unlikely. A slack and mixed up flow is looking more likely; if you like snow, thats much more favorable than the dry Easterly set up.

The way the models are integrating low pressure from continental europe flowing over the UK are what brings the 'fun'. However, these lows, the ppn and actual temps at the time are nowcast events, looking at these from 7+ days out should be for general trend reference only.

There will be shortwaves developing over North Europe and the North sea. These temselves will hugely influence the flow and patterns, but these are typically not accruately progged until <96hrs.

Having a cold and frozen France will massively help margin events/attacks from the south/south-west; I am mainly looking at the cold pools over Europe with more interest than the complexities of movements of low pressure and slight changes in wind direction >144hrs.

As an illistration of where this cold spell may be going i will use the 168hr chart.

The 168hr charts alludes to the feb 91 Easterly.Not when it was at its most 'classic' shape, but when it involved a little bit more 'fun' for snow lovers from low pressure systems.

Feb 91:

168hrs: (next week forecast)

Interesting times ahead

[MKN]

Bbc weather just said temps next week are proberly going to take a plunge

Down from a high of 2c today.

[jessandjon]

Down from a high of 2c today.

Very true!!!

[BLAST FROM THE PAST]

Here's the situation as I see it developing and going along. Cold to very cold air embedding itself over the UK and westward from a decent easterly. The overall signal is for the HP to our NE to extend / retrogress towards Greenland and Iceland. Now this is the interesting bit and the crucial bit for longevity, there is likely to be an attempted eastward assault from troughs, however, from the SW. Due to the retrograde the block wont sink or retreat E or SE. Thus the LPs will bump and grind along the southern flank and eventually we could see the trough settle to our east as the HP settle more to our N/NW with a NE'ly flow. It will elongate the cold pattern and indeed re-inforce a further colder shot down the line later in the month if the retrograde occurs. Southern half at risk of highest snow accumulations initially transferring to NE later. The key is the retrogression, that must occur/continue.

BFTP

[craigore]

I think a full blown, dry and straight easterly is very unlikely. A slack and mixed up flow is looking more likely; if you like snow, thats much more favorable than the dry Easterly set up.

The way the models are integrating low pressure from continental europe flowing over the UK are what brings the 'fun'. However, these lows, the ppn and actual temps at the time are nowcast events, looking at these from 7+ days out should be for general trend reference only.

There will be shortwaves developing over North Europe and the North sea. These temselves will hugely influence the flow and patterns, but these are typically not accruately progged until <96hrs.

Having a cold and frozen France will massively help margin events/attacks from the south/south-west; I am mainly looking at the cold pools over Europe with more interest than the complexities of movements of low pressure and slight changes in wind direction >144hrs.

As an illistration of where this cold spell may be going i will use the 168hr chart.

The 168hr charts alludes to the feb 91 Easterly.Not when it was at its most 'classic' shape, but when it involved a little bit more 'fun' for snow lovers from low pressure systems.

Feb 91:

168hrs: (next week forecast)

Interesting times ahead

I see what your getting at ,but wasent it a lot colder feb 91??

[Frosty.]

Here's the situation as I see it developing and going along. Cold to very cold air embedding itself over the UK and westward from a decent easterly. The overall signal is for the HP to our NE to extend / retrogress towards Greenland and Iceland. Now this is the interesting bit and the crucial bit for longevity, there is likely to be an attempted eastward assault from troughs, however, from the SW. Due to the retrograde the block wont sink or retreat E or SE. Thus the LPs will bump and grind along the southern flank and eventually we could see the trough settle to our east as the HP settle more to our N/NW with a NE'ly flow. It will elongate the cold pattern and indeed re-inforce a further colder shot down the line later in the month if the retrograde occurs. Southern half at risk of highest snow accumulations initially transferring to NE later. The key is the retrogression, that must occur/continue.

BFTP

That would be brilliant Blast, win win for the uk and that seems to be the likely longer range trend, so we get blasted by easterlies next week, then gradually the winds back towards the north east or north later, the current ens mean signal though is for the easterly to gradually back more south easterly as the scandi high pushes further north east and low pressure advances from the southwest, lots to look forward to next week though with wintry showers (snow and hail) becoming more widespread in the east and pushing west south west on bitter ENEly winds.

[Summer Sun]

Ben Rich on the news channel just a moment ago temperatures will turn milder briefly over the weekend (wind chill will make it feel cold though) before they plunge next week as winter bites back

The models are certainly on to something here that's for sure

Edited December 6, 2012 by Gavin.

[weather eater]

Yes, there is absolutely no point anyone getting hung up on this, the METO have to mention it in their updates because they see the possibilities of Atlantic attacks but don't forget that the models will always want to break down a blocked set-up quicker than is likely.

I think the sort of set-ups being progged in FI gave the West Country some huge snowfalls in the classic winters of years gone by. It is potentially more complex than a Scandi block being attacked from the SW because the HP belt could be aligned across towards Iceland. Anyway, I would be surprised to see an attack from the SW or S this side of T240.

Very true Ian, in fact some of the county’s most memorable snowfalls have occurred in the SW, including one report from the edge of Dartmoor, (In I think the 1920s, will have to check) of 6 ft of undrifted snow, it was described as being shovelled out of the sky.

[akelly1962]

Hi I'm a total newbie to this but am always checking this forum. Any thoughts for Ireland easy side.

[akelly1962]

Sorry meant to say east side eg dublin. I have a very keen interest in weather especially cold and snow. Met eireann not giving anything for next week. Models look for the uk though.

[Nick F]

http://www.meteo24.f...html?eps=london

Yes noticed that but London ECM ensembles show the control is colder for London than it was for De Bilt and the mean around the same as it has been the last few days. Like y ou said, the UK could possibly stay colder for longer and I think this is what we might see in this situation. London ensembles may become a better guide than de bilt.

Matthew

The 06z GFS T850 ENS for London show a lot more scatter after the 12th than those for Aberdeen too, which suggests the uncertainty further south over the potential attack from the SW on this run.

- London

- Aberdeen

Though I think the GFS is often too progressive in trying to break down cold blocks, such as the one that seems likely to back west across Nern Europe next week.

However, even if we do get an attack from the SW, and if the cold block holds or not, we could of course see some significant snowfall somewhere in the next few weeks, akin to those we see across the eastern seaboard of the US

Edited December 6, 2012 by Nick F

[adalton]

Sorry meant to say east side eg dublin. I have a very keen interest in weather especially cold and snow. Met eireann not giving anything for next week. Models look for the uk though.

Met Eireann have this on their site:

Next week will be extremely cold with east or northeast winds and day time temperatures of between 2 and 5 degrees. Night time values will drop as low as -5 or - 6 degrees. There'll be widespread frost, fog and icy stretches at night and each morning. Monday and Tuesday will be dry and bright. From Wednesday onwards there'll be an increasing risk of wintry showers of sleet or snow near east and north coasts.

[weather eater]

Was that the famous Tavy Cleave (sp?) one?

Edit : I think this happened in March 1891, so probably not the one you mean.

Holne Chase 6ft in 15hrs, 1929, but we digress, 12z out shortly, the thread will soon be revving up for that.

Edited December 6, 2012 by weather eater

[Bonjangle]

Holne Chase 6ft in 15hrs, 1929, but we digress, 12z out shortly, the thread will soon be revving up for that.

12z Looking forward to that and also all the peeps on here overloading this Thread , makes my day run smoothly .

[Paul_1978]

What does 'retrogression' actually mean, in laymans terms?

A word I see on the thread regularly but not sure if I've got my head round it!

[Bonjangle]

What does 'retrogression' actually mean, in laymans terms?

A word I see on the thread regularly but not sure if I've got my head round it!

either moving backwards or in a reverse direction i think .

[Panayiotis]

What does 'retrogression' actually mean, in laymans terms?

A word I see on the thread regularly but not sure if I've got my head round it!

Normally used when high pressure from Scandi 'moves' west into Greenland.

[weather eater]

What does 'retrogression' actually mean, in laymans terms?

A word I see on the thread regularly but not sure if I've got my head round it!

I would say the movement of areas of pressure from East to West, sometimes from South to North though I wouldn’t use it that way. For instance the block moving from Scandinavia to Greenland.

[PubliusEnigma]

I think a full blown, dry and straight easterly is very unlikely. A slack and mixed up flow is looking more likely; if you like snow, thats much more favorable than the dry Easterly set up.

The way the models are integrating low pressure from continental europe flowing over the UK are what brings the 'fun'. However, these lows, the ppn and actual temps at the time are nowcast events, looking at these from 7+ days out should be for general trend reference only.

There will be shortwaves developing over North Europe and the North sea. These temselves will hugely influence the flow and patterns, but these are typically not accruately progged until <96hrs.

Having a cold and frozen France will massively help margin events/attacks from the south/south-west; I am mainly looking at the cold pools over Europe with more interest than the complexities of movements of low pressure and slight changes in wind direction >144hrs.

As an illistration of where this cold spell may be going i will use the 168hr chart.

The 168hr charts alludes to the feb 91 Easterly.Not when it was at its most 'classic' shape, but when it involved a little bit more 'fun' for snow lovers from low pressure systems.

Feb 91:

168hrs: (next week forecast)

Interesting times ahead

And this is an extract of the forecast from Feb 1991

Edited December 6, 2012 by PubliusEnigma

[Met4Cast]

What does 'retrogression' actually mean, in laymans terms?

A word I see on the thread regularly but not sure if I've got my head round it!

Retrogression; Moving backwards

When High Pressure moves from Scandinavia West towards Greenland we refer to it as Retrogression because it's moving against the prevailing West - East flow. Talks of retrogression often mean cold weather could be on the way!

Edited December 6, 2012 by Daniel AKA WMD

[latitude]

And this is an extract of the forecast from Feb 1991

You wont get that will the slack flow being modelled.

[Weathizard]

And this is an extract of the forecast from Feb 1991

Never seen that before, was before I was even a glint in my dads eye!! Incredible to see that sort of forecast though, not often you see weather like that, I doubt we'll get anywhere near that standard, in our dreams maybe!

What I'm going to do today, as well as comparing 6z to 12z. I'm going to compare yesterdays 12z to todays 12z. Lets hope for more upgrades today!

[paul tall]

And this is an extract of the forecast from Feb 1991

Aaaaaaah! I remember that week well - we got buried!

In fact I remember watching that actual forecast1

[P-M]

You wont get that will the slack flow being modelled.

Erm........

[Paul_1978]

Many thanks for all the replies regarding 'retrogression'!