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Model output discussion - 7th January onwards


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Please keep this thread solely to discussing the model output. The model banter thread is available for more loosely model related chat, ramps and moans.

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4 minutes ago, Nick F said:

Afternoon all

After some uncertainty with regards to the track of a winter storm over the eastern USA this weekend and how far out into the far north Atlantic it will track and interact or phase with low pressure ahead of it near Iceland diving southeast towards the North Sea Tuesday, it appears the models are starting to converge on the idea of low pressure over North Sea Tuesday dropping southeast across mainland / central Europe into Wednesday, while pressure / geopotential height rises build in to the north of the UK and over Scandinavia

The buckling of the jet over the far north Atlantic ahead of that storm passing Nova Scotia Tuesday and jet stream downwind over the NE Atlantic turning southeast as a result, allows low pressure to dive southeast from Iceland towards the North Sea then into mainland EU and looks to be the main trigger for pressure to build to the north and northwest of the UK later next week.

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However, there are also signs, from the ECMWF high resolution, of an arctic high forming over eastern Greenland, I mentioned this yesterday too, perhaps in response to easterly winds starting to propagate down through the troposphere from the lower stratosphere – following the Sudden Stratospheric Warming to start the year.

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EC, with its better vertical resolution, probably get a better handle on the downwelling and how it will affect trop patterns and yesterday's EC stratosphere charts on the Berlin site showing easterly winds finally reaching down into the troposphere by the middle of next week.

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06z GFS also has the easterlies reaching down through the troposphere, perhaps a few days later

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This arctic high has, on a few ECMWF runs now, been indicated to drop south to Scandinavia intensifying high pressure there, this and the sequence of events leading to the flow buckling northeast over the Atlantic portending to an easterly or northeasterly flow to develop towards the tail end of next week. 

However, there is still a fair bit of uncertainty how the synoptic pattern will evolve in detail for now beyond Wednesday, suffice to say an increasing risk, say 70%, for very cold air and increasing snow risk to arrive from NE Europe by the end of next week or next weekend. This very cold pattern could be sustained into early January, thanks to the delayed and slow downwelling of easterly winds in the stratosphere impacting circulation in the troposphere but over a protracted period too, so high latitude blocking could persist for a few weeks at least.

Before then, worth keeping an eye on Monday night - active frontal system diving SE with quite cold northwesterly flow immediately behind coming from a very coold Greenland and NE Canda, 00z ECMWF was not overly keen on back edge  snow away from more northern areas, 00z and 06z GFS show back edge snow all the way to southern England. Sleet and snow showers packing in behind across the northwest.

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Thanks Nick, all makes sense in there.

One small typo, you mean into February not January?

 

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I assume the overnight ECM has (temporarily at least) put an end to the glass half empty stuff from some posters yesterday. I'm sure the next variation in op run will bring them back out - but if you

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Just now, johnholmes said:

Thanks Nick, all makes sense in there.

One small typo, you mean into February not January?

 

Yep, just notice and changed

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This potential cold spell is also going to fall in just about the optimum time for cold as well. The equivalent of big summer heat towards the end of July/beginning of August. It’s all looking good - at the moment!

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10 minutes ago, kold weather said:

Right everyone, eyes down because the 12z suite are upcoming, starting with the intial stages of the ICON 12z, out to just 12hrs.

Next 4 hours are going to be either very stressful, very sad....or VERY happy.

As long as we continue to see the broad trend of HP forming either to our north or east then the rest will hopefully come in tow.

Best of luck, everyone!

Tis like bingo in here..Well Im hoping for a full house..!!

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ICON has the low MUCh further SE at 108hrs coming out the states, though still worth noting there is a fair amount of lower heights over Iceland this time but looks like a decent start.

Looks like things are further west, for example the upper high is further west to our north (and weaker).

Edited by kold weather
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9 minutes ago, CSC said:

Sometimes surprises for snow in short term can happen and I do think there is the chance of snow Tuesday right down to the South Coast.

A very nervous few hours await..

 

Not convinced - experience tells me that these marginal events tend to fall the wrong side as they come into the 36-72 range. Rather like tonight's prospects were looking a couple of days ago. Not a problem, as this was only the breadstick course.

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42 minutes ago, tight isobar said:

Well for all the talk of brexit etc..

This one up n, coming could put the agenda/issue to the bk of the pack 4 a while...

And our weather could become the main headlines....

Into the freezer we go...

And the rest of europe joins us..

No getting out of this 1 theresa!!!?

temp4 (3).png

Sorry, I maybe being dumb, but don't those first 2 charts indicate only the West of the UK getting cold conditions and everyone else getting between 0-4c which is cold but nothing out of the ordinary, just typical winter temperatures?

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5 minutes ago, Stu_London said:

Not convinced - experience tells me that these marginal events tend to fall the wrong side as they come into the 36-72 range. Rather like tonight's prospects were looking a couple of days ago. Not a problem, as this was only the breadstick course.

A good point.. 

The timing of the low on Tuesday is mixed on many different models. A 6 hour difference could mean the low from the NW hits colder air than what is forecast. Maybe the snow laying is far fetched, especially for the S and SE coast but certainly not impossible at this range. 

None the less, you need the ingredients before you make the cake and as you rightly stated, this is only the start of what could be a memorable spell of wintry weather.

Edited by CSC
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4 minutes ago, Stu_London said:

Not convinced - experience tells me that these marginal events tend to fall the wrong side as they come into the 36-72 range. Rather like tonight's prospects were looking a couple of days ago. Not a problem, as this was only the breadstick course.

Agreed, nearly always Jam side down. Can't remember the last time a marginal event flopped in our favour along the south coast. 

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Just now, Alderc said:

Agreed, nearly always Jam side down. Can't remember the last time a marginal event flopped in our favour along the south coast. 

always a big ask to get settling snow down that far south

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Just now, kold weather said:

Well 12z ICON is a bust because the upper low doesn't cleanly come south and leaves a lobe of energy near Scandinavia so it all kinda flops and a LP comes through the gap.

Those Austrians would soon find the snow depth reaching the top of their mountains !!

seeing as icon doesn’t seem to have grasped this whole evolution thus far we can hope it’s still struggling....

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Just now, Fender.. said:

always a big ask to get settling snow down that far south

Absolutely, only really polar lows moving east to west or channel lows in most cases which is why down here I'm not really interested unless uppers are around -10C, anything higher its too marginal. 

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Just now, kold weather said:

Well 12z ICON is a bust because the upper low doesn't cleanly come south and leaves a lobe of energy near Scandinavia so it all kinda flops and a LP comes through the gap.

As last night, this remains a source of concern for me in the shorter term - there's been quite a few examples of clean separation of lower heights being modelled at extended timelines, only for smaller shortwave features to crop up the closer we get to T+0 and spoil the first bite of the cherry

Fortunately, this is just the ICON, and despite what anybody might suggest on here, it still verifies poorly compared to the EC, UKMO and even the GFS - so nothing to panic about for now

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1 minute ago, bluearmy said:

Those Austrians would soon find the snow depth reaching the top of their mountains !!

seeing as icon doesn’t seem to have grasped this whole evolution thus far we can hope it’s still struggling....

Its funny because the upstream actually does look better, the US low looks more favourable early on in the run, but this time its on our side that things go wrong!

Ah well, the GFS coming up soon! We should know by 4pm what type of run its going to be, happy or sad!

Edited by kold weather
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Just now, bluearmy said:

Those Austrians would soon find the snow depth reaching the top of their mountains !!

seeing as icon doesn’t seem to have grasped this whole evolution thus far we can hope it’s still struggling....

Or we all move to Austria. 

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1 minute ago, Alderc said:

Agreed, nearly always Jam side down. Can't remember the last time a marginal event flopped in our favour along the south coast. 

It might surprise but we haven't really had many penetrating frosts to cool the soil down (last night was about -1)

However as per previous post, we are only really taking are seats for dinner at this stage. The table is booked for the whole evening and the reliable models are screaming after hours lock-in.

Hopefully ICON isn't the babysitter that will call and tell us we have come home because little Johnny has been sick down his pyjamas.

 

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anim_sdc0.gif anim_xxy4.gif

We can see where the ICON kills the pattern. At around T138 the next wave (far SW), instead of joining the Atlantic ridge it gets blocked off by a cut off low. It then forces the pattern east rather than pumping warmer air north via the Atlantic ridge. GFS 06z for comparison.

One to watch...

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