Model Output Discussion - 18z 31/10/15 onwards

[BlueHedgehog074]

A glance at the latest fax's show,in the short term,the troublesome wavering frontal systems bringing the pulses of heavy  rain to some areas over the next few days....

Indeed Phil. A lot of action-packed weather for many places, particularly for North-Western UK areas, in the next few days. Though I know as a lot of others have said, some care will need to be taken with that likely flooding risk for Western and Northern areas.

Interestingly, for those who like cold weather, the 10 day 500mb outlook chart from the NOAA tonight seems to be continuing to head in a chillier direction with some kind of ridging and high heights likely in the Atlantic forcing some kind of downstream troughing over and to the East of the UK. This of which could help bring some chilly bursts of air down from between the West or North (especially with a mean 500mb North-Westerly flow over the UK) and perhaps a chance for a wintry mix of weather for places, especially Northern UK. With heights over the UK being a little lower than average, it could support disturbances slipping down from the North-West (or perhaps North) to bring some wintry possibilities. Otherwise, it does look encouraging for a colder period of weather to develop for a time and does follow similar ideas to a number of the operational models tonight.

http://www.cpc.ncep.noaa.gov/products/predictions/610day/500mb.php

Maybe would need another update or two from these anomaly charts to have additional confidence for next weekend's possible cold spell/snap as it is still a few days away. And there's always a risk that something could spoil the party for cold weather developments, even though there is some pretty decent support for a chillier spell. (For the cold weather fans, hopefully this won't be one of those situations. Wouldn't mind seeing an early wintry spell).

Edited November 14, 2015 by DiagonalRedLine
To add quote from Phil's post, plus added the 'even though there's pretty decent support for a chillier spell'.

[radiohead]

18Z GFS looks a little less amplifed than the 12Z at this point. The 12Z was in turn a little less amplified at this point than the 06Z. Hopefully this isn't a trend or we won't even have a toppler!

[knocker]

Funny how things change. You post chart after chart showing low heights over Greenland. Then when pressure does rise over greenland you forget to dicuss what that actually could mean for the UK and talk about westerlys at T360!!

 

I haven't a clue what you are talking about, have you? When exactly have I been posting chart after chart showing low heights over Greenland? The post you quoted was just just this evening's anomalies and I did discuss, albeit briefly as is only meant as a general comment, what it could possibly mean to the UK. The T360 was just the end of ext ecm and just mentioned in passing. I would be obliged if would explain what you find so objectionable about that and if you have a specific problem with my post(s) just spell it out.

Edited November 14, 2015 by knocker

[knocker]

My observation on the extended eps knocks, is the Atlantic anomoly pushing back north days 11/12 before it falls away and a lowish anomoly drops into nw Europe for the end of the run, (all the time post day 10, a euro low anomoly persists, though not too low). Will be interesting to see how much the clustering is on the cold side for London re that low euro anomoly.

 

Yes I wouldn't argue too much with that blue as I wasn't attempting to describe the whole of the ext period (being in a hurry at the time). I don't think the weak Euro low of any particular consequence so all in all a fairly benign westerly flow.

Edited November 14, 2015 by knocker

[ANYWEATHER]

No, you rightly point out the distinction between snow *falling* versus *accumulating*. And yes, ongoing depth temperatures at many lowland sites are likely to mitigate against anything other than temporary settling. However, this depends on PPN rates too. Either way, it's too early to even discuss snow in any semblance of reality. The actual pattern is yet to be resolved... it's still effectively a whole week away. For what it's worth, last two EC runs accumulate truly measurable snow only over northern uplands (Snowdonia/Pennines northwards). But it's only November, so it'll take a proper run of ongoing cold conditions to drop depth temps down into a reliable window for prolonged settling, irrespective of diurnal cycle.

I really see any real wintry stuff confined to northern Britain next weekend and that is subject to big change! If the models are correct there will be some real fireworks over any places exposed to the freezing airmass Ie West Wales where I will be parked just in time if that does verify !

[bluearmy]

Yes I wouldn't argue too much with that blue as I wasn't attempting to describe the whole of the ext period (being in a hurry at the time). I don't think the weak Euro low of any particular consequence so all in all a fairly benign westerly flow.

If there is a euro low then there will have to be a ridge somewhere between that and an Atlantic regime. Note that the extended ECM ens mean has a very weak Atlantic jet stream. Within the mean westerly dam lines, I expect to see an Atlantic area of high pressure through week 2. Too early to say how far south it might end up being. And if it's there, an upstream inland running system could well retrogress it.

[snowking]

It's very much worth noting that the ECM ensembles, even at the day 5-7 range, diverge into two camps in terms of the strength of any heights across the Greenland locale. Both clusters send a ridge into that region but one is distinctly more robust looking than the other.

 

Beyond this things become a bit of a mess so probably best not to pay too much attention to the suite in terms of longwave pattern beyond this (the ENS means are likely to be rather diluted this evening) but the majority favour things at the surface at least remaining a little closer to average or even slightly on the chillier side

 

SK

[knocker]

If there is a euro low then there will have to be a ridge somewhere between that and an Atlantic regime. Note that the extended ECM ens mean has a very weak Atlantic jet stream. Within the mean westerly dam lines, I expect to see an Atlantic area of high pressure through week 2. Too early to say how far south it might end up being. And if it's there, an upstream inland running system could well retrogress it.

 

What exactly do you mean by, "an upstream inland running system"? Anyway what the heck this is the chart for day 12 and I thought we had already agreed the ridge. And the flow flattens by the end which is not altogether unexpected.

Edited November 14, 2015 by knocker

[snowblizzard]

What exactly do you mean by, "an upstream inland running system"? Anyway what the heck this is the chart for day 12 and I thought we had already agreed the ridge. And the flow flattens by the end which is not altogether unexpected.

Really sorry but, I've never really understood these anomaly charts.

Could someone please explain what they mean/show and what the blue, yellow, red area's indicate?

[Mucka]

GFS 18z was more of a sinker/stinker than a toppler wasn't it?

Still a mixed bag in the ensembles though from stinkers to winter charmers.

Here are a few to keep the spirits up until the next runs.

 

 

 

I think we need a lot to go right to have a chance of lying snow in lowland England from this as things stand and I a have more hope of a proper wintry spell form a ppossible reload end of Nov early Dec.

Whatever we get this time around fingers crossed the pattern doesn't flatten out and we get zonal Dec.

[Yarmy]

Really sorry but, I've never really understood these anomaly charts.

Could someone please explain what they mean/show and what the blue, yellow, red area's indicate?

An anomaly is a departure from average. The yellows and reds mean higher than average heights in the Iceland area, and the blues mean lower that average heights over mainland Europe.

FWIW, I don't like the term "anomaly" as it suggests something unusual, but we are stuck with it.

[Nick F]

Do wonder whether ECM maybe over-amplifying the Greenland positive height anomaly in response to the deepening trough upstream over N America next week. Certainly 18z GFS and 12z GEFS mean showing a flatter upper flow over the N Atlantic. Though still enough amplitude later in the week/early weekend to allow a brief bitter arctic incursion by Saturday that would bring wintry showers south. But still maintaining a cold Pm flow from the NW thereafter at least.

Over amplification or not, GFS and EC deter to day 10 broadly agree on persisting wave pattern of upstream ridging over NE Pacific, troughing over N America and downstream ridging over the Atlantic, troughing digging deep into Europe. The GEFS mean indicating the wave pattern flattening with time over N America and NW Atlantic, whilst EPS mean nudges the N American trough and downstream +ve height anomaly over the NW Atlantic further east.

So, the cold and wintry weather still likely on to arrive at the end of the week, but question marks on how long the sub -5C T850 flow can maintain before the flow flattens out and the cold polar or Arctic flow is diluted.

Edited November 14, 2015 by Nick F

[knocker]

Really sorry but, I've never really understood these anomaly charts.

Could someone please explain what they mean/show and what the blue, yellow, red area's indicate?

 

I was just about to answer when I notice Yarmy has already done so. Some time ago JH did a more detailed answer using the NOAA charts which may be of interest.

500mb charts-are they a useful guide-8 feb 12.pdf

[johnholmes]

NOAA has joined ECMWF-GFS 500mb anomaly charts with, see below, a noticeable ridge for the Greenland area and an equally noticeable trough east of the UK. It is only one output but it is rare for these 3 to be very similar and the pattern they are predicting not to occur. So nextweekend and possibly 3-5 days it would seem for a colder upper flow into the UK. Beyond that and a more westerly looks like being the pattern. That is based on the past 24 hours but it may change. As to how cold, when/where any snow then obviously that comes several days from now with the synoptic models.

CAUTION:- Do be aware that predicting anything falling from the sky is very difficult even 12 hours ahead, snow and you need to add about 6 possibly 8 more variables into the mix, obviously one of these is your height above sea level.

http://www.cpc.noaa.gov/products/predictions/610day/500mb.php

[Cheshire Freeze]

0z GFS- looks a lot more like the GEM upstream at this early stage- better amplified with deeper troughing further S over the other side of the pond

 

 

Snow showers digging S with uppers of -8 sinking southwards too

 

Edited November 15, 2015 by CreweCold

[Mucka]

Morning Crewe, think you're still bleary eyed, you mean 00z 

 

Some pretty cold 850's on this run with a band of snow moving South.

 

 

I would take that at this stage I think.

 

Another poor UKMO though, sinker.

 

Edited November 15, 2015 by Mucka

[Cheshire Freeze]

Morning Crewe, think you're still bleary eyed, you mean 00z 

 

Some pretty cold 850's on this run with a band of snow moving South.

 

 

I would take that at this stage I think.

 

Another poor UKMO though, sinker.

 

 

Oops yes- just on my way to bed, edited now. Yes UKMO poor and GEM at 90 hours looks to be a slight downgrade on the 12z. Lots still to be resolved upstream obviously!

 

I'd 'deal' on the 0z GFS too.

Edited November 15, 2015 by CreweCold

[Mucka]

Oops yes- just on my way to bed, edited now. Yes UKMO poor and GEM at 90 hours looks to be a slight downgrade on the 12z. Lots still to be resolved upstream obviously!

 

I'd 'deal' on the 0z GFS too.

 

LOL thought you were just getting up rather than just going to bed, I guess it was Saturday night - you young uns eh?   

Yeah upstream far from resolved so just a case of enjoying the run to run rollercoaster at the mo.

I'm keeping my eye out for potential reloads though as I think it could lead to a proper cold spell if it happens.

Edited November 15, 2015 by Mucka

[knocker]

This morning's gfs is not without interest. It initiates the 'cold Plunge' around Saturday and maintains until Thursday ( and quite cool for a period after that) when the HP makes ingress from the west. the upper trough in fact drags the cold air down to North Africa.

Charts weatherbell

Edited November 15, 2015 by knocker

[solarcycle]

This morning's gfs is not without interest. It initiates the 'cold Plunge' around Saturday and maintains until Thursday ( and quite cool for a period after that) when the HP makes ingress from the west. the upper trough in fact drags the cold air down to North Africa.

Charts weatherbell

Thanks knocker. When you post about cold I can believe it might happen.

[dragan]

This morning's gfs is not without interest. It initiates the 'cold Plunge' around Saturday and maintains until Thursday ( and quite cool for a period after that) when the HP makes ingress from the west. the upper trough in fact drags the cold air down to North Africa.

Charts weatherbell

Knocker the voice of reason,

to me it looks like a fairly chilly high pressure once/if it gets established, how do you read this?

Thanks

[knocker]

Well that certainly could be the case but i wouldn't read anything into the evolution at that time frame, especially on the strength of one run. The clever money is looking at temps around average but best wait a day or two for any particular evolution to firm up.

Thanks knocker. When you post about cold I can believe it might happen.

 

You know me solar. objectivity is my second name.

[bluearmy]

I'm wondering how much the Siberian ridge is going to be displaced south and East and how amplified the ne Pacific can become. the former will dictate how sustained any Scandi trough might be and the latter how flat upstream might become. the entire gamut of solutions available across the GEFS members through week 2!

would plump for a more seasonal last third of the month here with the odd surprise chucked in. Average to cool, occasionally cold. hardly a brave prediction but the likelihood of ridge or trough across nw Europe is really 50/50 imo so detail elusive to say the least.

EDIT: the ECM op delivers a light covering Friday night in the se/ea. exposed upland areas UK favoured for some reasonable cover fri thru Sunday.

Edited November 15, 2015 by bluearmy

[tinybill]

http://www.meteociel.fr/modeles/gfse_cartes.php?mode=2&ech=6

 

well  with the horrible weather to-day  once the coldies see what coming  later   things could get a touch cold  soon :cold:

[Polar Maritime]

The GFS this morning continues to show a very cold wintry blast from the North next weekend, With -8/-9 even a cluster of -10 850's pushing South over a vast swath of the UK. After a very stormy week coming up..

Edited November 15, 2015 by Polar Maritime