General Model Output Discussion

[igloo]

i cant see the atlantic very happy being blocked for a fortnight or so.im sure it will hammer us stupid for the best part of january with past experiences.

[Don]

If my memory serves me correctly, wasn't there a stratospheric cooling event at the end of December last year, which saw the return to more zonal conditions after the first week of Jan, but this was of a cooler zonality type? Todays BBC monthly update certainly hints at cool zonality as we move through January

[geoffw]

as i said earlier we need gp to explain what is going. Im very worried we will see a flat jet and low after low for the whole of Janruary. Is anyone feeling the same or am i over-panicking?

I know gp stated we would get a milder interlude before we get severe cold mid-jan onwards in his winter forecast. Is this still true? Also, does anyone have a link to his forecast so i can re-read it?

Edited December 21, 2009 by geoffw

[karyo]

I suppose there must be examples of cold winter months despite a cold stratosphere, but it's risky, especially with the el nino in force!

Karyo

[weather eater]

A return to rampant zonality does not seem on the agenda according to GPs last post on the technical discussion thread.

[Thundery wintry showers]

I think all this concern about a PV return at T+240 is rather looking too far ahead at this stage given the uncertainty involved. Certainly, I can see potential for some kind of northerly toppler event on around 27-29 December but by this stage we're out at >T+180 again- not the best of timeframes to be looking for changes! With the jet tracking quite a long way south I think any zonality would be likely to be of the cool zonal type anyway.

[Richard Lake]

Funny how when exciting-low temperatures are being shown more than 10 days in advance no-one really believes it will materialise yet when mild temperatures are being shown the majority believes its definitely on the cards. I think people have to be more open minded and not look past 4 days as the best weather forecasting models in the world aren't really that great after all.

[Snow Queen one]

Well so many times the temps have been right for milder weather so people tend to err on the side of caution. We have been fooled by the models before so find it hard to trust what they say. This spell however has been different in so much as we all hoped the cold would come but didn't quite believe it would so now it is here it is too good to be true and people are looking to the models to see when it will go.

We as weather watchers are a fickle lot. lol

[Thundery wintry showers]

I'm sure that milder weather is on the cards because it has to turn milder eventually (yes, even the severest winters had occasional mild interludes) but I also think it will be temporary.

The models are strongly agreed that something less cold, albeit probably still a little below average in the north, will move up from the south-west during Boxing Day. This will bring a thaw except on high ground. However it may not last as the low pressure looks set to move away eastwards, and another low take a southerly track across the south allowing cold Arctic air to return into northern areas, and probably, eventually, southwards across the whole country.

[J10]

I think most people would take this chart if the Meteociel chart accuracy is good.

Even the NW Snow Forecast charts, while not being as snow laden, would give a sleetinees to technically give a White Christmas for many.

[azores92]

couldnt it also be argued that a cool stratosphere could lead onto a surface high developing over the united kingdom, which was what TWS was suggesting earlier. this would keep the cold going and bring fog and frost a plenty. im not convinced the further outlook is conducive is the jet firing up over greenland leading us back to full blown zonality, and as GP has hinted at a ridge over iceland, i am certainly not buying into the wet and windy january just yet. going by the lrfs, few have called a mild wet and windy january. as someone else said, this time last year we were looking at a similar scenario in the stratosphere, and jan 09 was hardly blowtorch?

[swfc]

Good run this from gfs.The only thing that can kill it is the low coming off the usa.?????

Edited December 21, 2009 by swfc

[Thundery wintry showers]

Still don't like the way that evolution would thaw any snow near the east coast of England just in time for Christmas Day and give a dull drizzly sleety day to those regions- indeed even inland it looks pretty marginal. I'd take a snow cover over a thaw and a bit of sleetiness on the big day. However for some central regions it could add a wintry flavour to Christmas Day which could otherwise be cold and dry with no snow in the air or on the ground. I'm very surprised no-one else seems to have picked up on the likelihood of that system bringing a thaw to currently snow-covered areas, and I guess most of those who see these GFS runs as upgrades are coming from the midland counties that see an upgraded chance of the white stuff.

Still up in the air though as the ECMWF and UKMO outputs for Christmas Eve look rather different to the GFS. Will tomorrow's runs, a mere 2-3 days from the event, come into agreement at last?

Edited December 21, 2009 by Thundery wintry showers

[Troubleatmill]

good agreement out to new year? you knows what is round the corner right now

http://www.wetterzentrale.de/pics/Rz50010.gif

Edited December 21, 2009 by arron123

[swfc]

Decent run but id put fi at 70 hrs.great long cold spell but know doubt gone in the morning

[damianslaw]

Increasing signs that the blocking to the NW over Greenland is about to relinquish its influence over our shores as we get past christmas day allowing a more westerly atlantic flow to move in resulting in a thaw for all expect higher ground in the north.

However, we maintain a southerly tracking jet and the prospects of a northerly of sorts developing early next week look quite high - whether this is just the pre-requisite for the atlantic to steamroller in on a more SW-NE trajectory who knows, it could be followed by mid atlantic blocking.

My hunch is for a temporary cool unsettled spell as we end the year and start the new, with the cold ready to pounch thereafter.

[Yozzer]

Taking a rest from model watching for couple of weeks. Will take this pub run with me though! Mild never quite makes it this far north, with a rapid reload and some real wintry weather throughout. Also seems to dovetail with Stewart's thoughts on the way the picture is panning out, so it may have some truth to it.

[Guest North Sea Snow Convection]

I think all this concern about a PV return at T+240 is rather looking too far ahead at this stage given the uncertainty involved. Certainly, I can see potential for some kind of northerly toppler event on around 27-29 December but by this stage we're out at >T+180 again- not the best of timeframes to be looking for changes! With the jet tracking quite a long way south I think any zonality would be likely to be of the cool zonal type anyway.

You do your own monthly forecasts and make suggestions as to how the models may pan out in the FI period (and beyond) so I am not sure that discussions about the further outlook here are any different or any less valid than your own - even if we are not 'forecasters' and are just humble members.

You have conceeded on a different thread that your own predictions for December have not panned out (which is quite acceptable of course ) but I think on that basis we should all be entitled to assess the further outllook on the basis that it is at least based on some background signals that are relevant to the outlook. I would agree with your own thinking that the models may just be defaulting to a zonal basis, but the thinking that I am applying here is, nevertheless, based on some facts.

Ironically as a well renowned cold and snow fan I am discussing a potential return to a milder type here, of which usually I would be put in a box as not ever being willing to discuss - so it seems a case of not being able to win perhaps

[john w]

good agreement out to new year? you knows what is round the corner right now :lol:

http://www.wetterzentrale.de/pics/Rz50010.gif

Id say there is actually a seemingly strong agreement for zonality, yes some of the scribbles on the plot would throw up any random output but actually there are a lot of consistant runs going for a westerly zonality on that chart

[Optimus Prime]

Don't often see the spaghetti charts being posted.

[Thundery wintry showers]

I think you've strongly misinterpreted that post- I was merely referring to the fact that some members are worried about a possible PV setting up at T+240 when it's way too far out to be getting concerned about, especially as some model runs in the past have progged the PV setting up at T+180 and failed to materialise.

I didn't say anything about it being inappropriate for people to discuss the future outlook- that's just what you've assumed. A model output discussion can and should, indeed, look at both short and long-term trends, but at the same time, it's worth pointing out when model uncertainty is so high that a particular outcome shouldn't be taken as gospel!

[ISAAC]

In the shorter term, an intense band of rain pushing accross England and wales Wednesday Night giving a possible 1-2 hour heavy snow event in parts of the North Midlands according to the GFS. Very marginal indeed.

Any thoughts?

Edited December 21, 2009 by ISAAC

[swfc]

Latest fax updates look slightly rank but tie in with ecm.All to play for after next weekend in my opinion. :lol:

[Supercell]

Still don't like the way that evolution would thaw any snow near the east coast of England just in time for Christmas Day and give a dull drizzly sleety day to those regions- indeed even inland it looks pretty marginal. I'd take a snow cover over a thaw and a bit of sleetiness on the big day. However for some central regions it could add a wintry flavour to Christmas Day which could otherwise be cold and dry with no snow in the air or on the ground. I'm very surprised no-one else seems to have picked up on the likelihood of that system bringing a thaw to currently snow-covered areas, and I guess most of those who see these GFS runs as upgrades are coming from the midland counties that see an upgraded chance of the white stuff.

Still up in the air though as the ECMWF and UKMO outputs for Christmas Eve look rather different to the GFS. Will tomorrow's runs, a mere 2-3 days from the event, come into agreement at last?

Have to agree with you there re: the dangers of wanting PPN over saving snow cover.

Going by recent model outputs, that potential snow event (although much is still to be decided) would produce, at best, a temporary top-up of what has fallen previously. Only for increasingly wet snow to wash it all away. I think, even with establish cold, this event is pushing the wrong side of marginal.

[Don]

This time last week, or at some point, according to some of the models at least, this cold spell should have broken down today! Now we're looking around Christmas Day or Boxing Day for less cold weather, so it goes to show. Not a bad run of cold weather in my view, even though I haven't done brilliantly in terms of snowfall.