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

[PubliusEnigma]

Tonight's GFS and UKMO have slackened off the easterly flow and made it more of a N to NE'ly at times in the south- this means colder weather than on previous runs, drier inland, but also snowier within 20 miles of the east coast. The UKMO charts in particular have kinks in the isobars which would be likely to be associated with heavy snowfalls over eastern England, extending from Northumberland to East Anglia, and probably SE Scotland as well. A slacker east to north-east flow was suggested by some of the ECMWF ensembles this morning, so it will be interesting to see if the ECMWF also slackens off the easterly flow tonight.

Given the fairly significant changes with this evening's runs so far, I remain cautious regarding the amount of showery activity we'll get off the North Sea next week- a slack anticyclonic dry type is looking like more of a possibility from tonight's runs for instance- but it almost certainly looks like turning very cold. The low-res part of the GFS 12Z run, ushering in a zonal type, is somewhat at odds with the teleconnection and other atmospheric signals for continued northern blocking so I would advise not getting too worked up over it.

But if it becomes too slack could we not see endless days of stratocumulus off the north sea and temps around 3 or 4 degrees staying just above freezing at night ?

Which is fairly typical pattern associated with a slack NE flow off the north sea ?

[Captain Shortwave]

I think the fi in this should be taken with a massive pinch of salt. Up to about Monday/Tuesday things looks pretty set, but what the trigger low does after this is paramount to how our cold spell develops. This run is silly from there on as that low goes south, then east, then back west and finally north. That low is officially doing a tour of Europe.

Likewise the runs preceeding this should also exhibit the same treatment. But still an Easterly is on the card, just what weather/wind/temperatures are the things up for grabs tbh.

[German Sheperd]

the mad house returns!

Know what you mean.........I thought for a minute reading this thread, I had gone back in time and this was Snowatch.

Anyway, good runs so far tonight, couldn't really expect anything better than last night TBH, and I think we're all in a really good postion moving forward to next week.

Awaits the ECM.

[egret]

The Atlantic wins the first battle by next weekend.

http://cdn.nwstatic....228/h500slp.png

well if that chart is correct we shall be cooking xmas lunch over open fires - plenty of fallen timber and pretty few power lines!

[Snowman.]

I would like to say that CFS picked this up a while ago and it seemed to materialize I would start to look to the CFS for similar trends it may not be good at closer range but its a very useful model as its TWO colder trends that its picked and actually pulled through!

[LomondSnowstorm]

Always a good tip when looking at the beginnings of a potentially major cold spell: don't take any model showing a swift breakdown past +120 as anything more than conjecture, certainly not when we're still 4-5 days away from the start of the cold spell. Models tend to be overprogressive with this and often handle it very badly, only to prolong the cold at relatively short range. For where we may go next, it's best to, for want of a better phrase, stick to your ensemble means and your teleconnections, and anything completely at odds with that is, more likely than not, pretty far from being accurate.

We still most of the details to be worked out over the coming days e.g. potential undercuts, direction of the flow, uppers, possible disturbances in the flow etc. but the important thing is that, broadly speaking, we're still on the same track we were yesterday, and that's the important thing at the moment for me.

[weather eater]

I suspect the GFS is struggling with the evolution but I wouldn’t dismiss it out of hand, here’s my chart save from the 3^rd, check it against the 12z 72hr chart it’s pretty similar and I would suggest that 72hr chart will be a reasonable match come 0hrs

[Summer Sun]

The 12z looks fine for snow in the east next week 2 exmaples below

[john mac]

This place is a joke!!!! A few changes on one run and the Prozac is being ordered! Get a grip!!!!! Does anyone bother reading what GP and others post. Or do you just take every run as gospel!!!!. Like TEITS and Steve said the cold spell will last longer if the gfs verifies.

[Rob K]

People that compalin about the "dry" flow... I remember with great clarity how people were moaning about the Jan 2010 NE flow being "bone dry". Then at 36 hours' notice this low cropped up and dumped several inches of snow across much of the south.

http://www.wetterzen...00120100106.gif

There was no hint of it even 2 days before - the models just showed a straight and slack flow.

My point it, trying to pin down specifics more than a couple of days ahead is pointless. Look at the bigger picture.

Edited December 6, 2012 by Rob K

[jessandjon]

Then again it all goes t*ts up!

What is wrong with this chart?

[GoonerGregg77]

Come next week, we'll be opening our fridges to keep our hands warm! Brrrrrrrrr

I was very excited by the ECM yesterday as everyone of the 2000+ members and guests were, but you just knew things would downgrade, and for the record, not verify. But the scope from the heights of the ECM's charts, to what they are currently showing now, well, there very good still! Those charts were so extreme, even 50% of that potential would be more than acceptable.

People worrying about a slack flow? N-NE, E, SE winds, anywhere from the east will be very cold, end of, and if there was precipiation, then it will be longer spells of. I'll be delighted. As regards to where snow will fall, forget about that for now, let's enjoy what's evolving in front of us and get the cold in place first, after all, look at it this way, I'd rather be seeing and hearing about real potentials and getting excited from it, rather than hearing about the possibilities of mild S Westerlies and rain!

Things could be brain numbingly boring this early in the winter, but there far from it!

Edited December 6, 2012 by GoonerGregg77

[Anti-Mild]

Know what you mean.........I thought for a minute reading this thread, I had gone back in time and this was Snowatch.

Hear hear, we'll be hearing from Bill Farkin and his waxwings next!

As always the 12z GFS way to eager to revert to zonality, the ECM will ease some worried souls when it comes out.

[DanDorsetUK]

I knew it, with years of watching the charts i knew last night was way too good to be true, Been used to being let down by GFS so many times, im pretty sure this will end up being a little cold for 4- 5 days at the most with dusting of light snow here and there and with the atlantic winning over. Its a good start for this time of year and hopfully a precursor of whats to come for Jan and Feb. But to be honest i think people got there hopes up way to quickly last night!

[Fred Sykes]

What is wrong with this chart?

Nothing if you like wind and rain!

[Snowman.]

What is wrong with this chart?

It's V FI wouldn't even happen but look at the central point of that low and pressure the is just SCREAMING mild, wet and zonal winds!

That wouldn't happen but it just really horrible to see!

[weatherguy]

If charts can downgrade, they can upgrade. Critical period still days away yet.

[kold weather]

I suspect the GFS is struggling with the evolution but I wouldn’t dismiss it out of hand, here’s my chart save from the 3^rd, check it against the 12z 72hr chart it’s pretty similar and I would suggest that 72hr chart will be a reasonable match come 0hrs

There is a rather large difference though between 72hrs and 240hrs difference, which is about the time things really go wrong on this run.

As long as its cold and we keep some form of upper high near Greenland/Iceland, we will do ok.

[Bristawl Si]

i read GP's post earlier today and that's good enough for me.

A number of people on here, incl some regs, are just posting comments to spark a reaction and they're prob at home getting v excited because following posts react to their posts.

[SMU]

http://www.meteociel.fr/modeles/gefs_cartes.php?code=0&ech=6&carte=1&mode=0

one last comment before the ECM- the 12z GFS control is bias to undercutting- ( you will have to trust me on that ) - looks much more realistic-

After reviewing the 12's one thing has developed at 120-144 is the for the UK to possibly sit in slack frigid air-

If you review ALL the models bar the GFS tonight then watch the evolution with the slider shortwave-

The slider shortwave at 144 is the biggest thing with the slack air tonight & is fantastic news to reinforce the cold...

S

[johnholmes]

Some rather premature posts in here, I do urge some of you to read your posts over several days. One does not need to know what the models are showing simply read some folks posts, up-down several times I won't say a day but certainly several times a week.

When the froth subsides a bit I will post my weekly look at what seems the probable weather pattern 6-15 days or so from now.

[Frosty.]

The Atlantic zonal back after T8 till the end of FI. Downgrades all the way.

nice to see you being positive for a change

Models look super for a very cold wintry outlook, late FI is trash, the cold spell will last for weeks!

[cooling climate]

Very good UKMO tonight plus the 12z control run wets the appitite.

I am not surprised really at the extended model output from the GFS and the

ECM this morning they both show a sausage shape high and I think it is only

natural that the models will over do this.

Once the models settle down in a few runs or sooner we will have the jaw

dropping charts again in the 144- 240+time frame.

[Nick L]

I knew it, with years of watching the charts i knew last night was way too good to be true, Been used to being let down by GFS so many times, im pretty sure this will end up being a little cold for 4- 5 days at the most with dusting of light snow here and there and with the atlantic winning over. Its a good start for this time of year and hopfully a precursor of whats to come for Jan and Feb. But to be honest i think people got there hopes up way to quickly last night!

We're in a maritime climate. The Atlantic will ALWAYS win. And I wish these overly-negative posts would have some charts to back up the drivel. The UK is under cold 850s all the way until 192 on the GFS...and then it just reverts to its default zonal overload setting.

Really, some posts I'm reading in here are ridiculous. Of course it was going to be a downgrade on last night.

[jessandjon]

Nothing if you like wind and rain!

I thought the big blue meant cold