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Model Output Discussion - The Start Of Winter


Paul

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Posted
  • Location: Drayton, Portsmouth
  • Location: Drayton, Portsmouth

So what do the anomalies have in store tonight.

 

The NOAA 6-10 has a broad area of weakfish low pressure Greenland east to Scandinavia which intrudes on the northern parts of the UK. Underlying this is the Azores high. Upstream not a huge amount of amplification with HP NE North America and SE Pacific and LP Alaska.

The 8-14 weakens the LP north of the UK a tad and moves it slightly east which allows a very weakfish positive pressure over the Atlantic linking to the NE American high. Also more influence from the HP in the eastern Pacific.

 

There are some variations with the GFS and ECM but they are on the same page.

 

This would seem to indicate no major changes in the overall pattern with LP to north and and probably a little further east with Azores HP to the SW maybe moving a tad east, So generally a continuation of the zonal flow.

 

Further down the line indications of an Alaskan ridge, LP N. America and HP from Greenland ridging south mid Atlantic and a more meridional flow. The evolution from here may be interesting.

 

814day.03.gif

 

Charts courtesy weatherbell

 

I hope you don't mind me focussing on just one of your charts Knocker, but just to add to what you say, if a proper freeze-up is what is wanted, this chart shows a good trend, as it suggests pressure is perhaps going to increase around the tip of Greenland in the 8-14 day period, whilst the Azores High stays mid-Atlantic - a possible way forward from this is a link up of Highs between the Atlantic and Canada, which would force any weather coming to us to be sourced nearer Greenland.

 

Of course, it is just one run and, besides, just a subtle shift from what we already have - but if we're going to end up with a freeze from the North, this is the direction things will probably need to go in.

 

Edit: Blessed Weather - just seen your post above, agreed.

Edited by rjbw
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Posted
  • Location: Manchester
  • Weather Preferences: Sunny and warm in the Summer, cold and snowy in the winter, simples!
  • Location: Manchester

GFS 18z Op has a think about setting up a cold pattern boxing day.

 

gfsnh-0-300.png?18

 

But decides against it.

Edited by Mucka
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Posted
  • Location: Camborne
  • Location: Camborne

Hi Knocker. I don't always agree with your posts but tonight I think your analysis (in both posts) is spot on. The anomaly chart for 28th Dec (copied below) is indeed very interesting, suggesting the UK could be in a bitter Northerly flow if it verified. Of course, it's a very long way off but it does tally with the thinking of several posters on here that the first real cold spell will arrive from the North. Softly, softly but is a trend developing?

 

attachicon.gifpost-12275-0-41469400-1418505948 NCEP GEFS 28Dec14.jpg

 

I'll sleep easy tonight then BW. :) Having said that I'm not sure there is any indication on that anomaly chart of any cold from the north. Agreed there may be northerlies for a time but that could easily revert to run of the mill NW then W.

Edited by knocker
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Posted
  • Location: Manchester
  • Weather Preferences: Sunny and warm in the Summer, cold and snowy in the winter, simples!
  • Location: Manchester

Here is p4

 

gensnh-4-1-348.png?18

 

Somewhat cherry picked but the 18z ensembles have the strongest signal yet for a pattern change around Christmas and i picked this chart not only because it is a thing of beauty but because it typifies the sort of pattern change GFS is toying with. Atlantic ridge - deep trough to east/Scandi with WAA into Greenland and possible Greenland high forming.

 

Fingers crossed this signal strengthens over coming days and Christmas could still be cold though likely any real cold will be the other side of Christmas. (should it happen!)

 

Edit.

Just to add GFS flattens out most attempts at building a strong Atlantic ridge but that is to be expected in deep FI

Edited by Mucka
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Posted
  • Location: Broxbourne, Herts
  • Weather Preferences: Snow snow and snow
  • Location: Broxbourne, Herts

Here is p4

 

gensnh-4-1-348.png?18

 

Somewhat cherry picked but the 18z ensembles have the strongest signal yet for a pattern change around Christmas and i picked this chart not only because it is a thing of beauty but because it typifies the sort of pattern change GFS is toying with. Atlantic ridge - deep trough to east/Scandi with WAA into Greenland and possible Greenland high forming.

 

Fingers crossed this signal strengthens over coming days and Christmas could still be cold though likely any real cold will be the other side of Christmas. (should it happen!)

 

Edit.

Just to add GFS flattens out most attempts at building a strong Atlantic ridge but that is to be expected in deep FI

I like P4 :) When runs like this are being produced, even if in apparent isolation, is it an indication that the PV is in a more fluid state and liable to move around more and perhaps throw off lobes in our direction?

And if that us the case, does it also mean that if such an outcome as P4 did come to fruition, it wouldn't necessarily mean a long term cold spell as the continuing fluidity of the PV then moves it away from the areas that benefit us for cold?

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Posted
  • Location: Manchester
  • Weather Preferences: Sunny and warm in the Summer, cold and snowy in the winter, simples!
  • Location: Manchester

I like P4 :) When runs like this are being produced, even if in apparent isolation, is it an indication that the PV is in a more fluid state and liable to move around more and perhaps throw off lobes in our direction?

And if that us the case, does it also mean that if such an outcome as P4 did come to fruition, it wouldn't necessarily mean a long term cold spell as the continuing fluidity of the PV then moves it away from the areas that benefit us for cold?

 

 

It can indicate that conditions in the Northern hemisphere will likely be more conducive for promoting HLB when we see it being modeled. If P4 was in total isolation it wouldn't mean anything but if you check though the charts of the ensembles and even the Op and control for around 25th/26th we can see there is clear potential for an Atlantic ridge to form which would be the first step to a possible cold spell. add to that the reports from Fergie and longer range anomaly charts and it amounts to a signal but that  doesn't mean it will happen or even if it does we will get deep cold.

No certainties in weather unfortunately but we do need a MLB or HLB to set up for a chance of sustained cold. After that, where any block sets up and how it orientates itself will determine if we get deep cold or not.

Usually if we can get a good Atlantic ridge and proper Greenland high we will get cold weather though it still depends on the above factors.

 

In short it is better to see it being modeled than not and the more we see it the better.  :laugh:

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Posted
  • Location: Manchester
  • Weather Preferences: Sunny and warm in the Summer, cold and snowy in the winter, simples!
  • Location: Manchester

Good morning.

 

GFS like a Dog with a scent. It knows there is a bone buried somewhere but it is going to have to dig a few holes before it finds it. (we hope)

 

gfsnh-0-336.png?0

 

Still no cold being modeled at the moment though.

 

 GFS (p) a bit of a dogs dinner. (Maintaining the theme)

 

gfsnh-0-276.png?0

 

So still plenty of uncertainty on what Christmas day will bring or if we will get a more blocked pattern as we get into the last week of December.

If the models do latch onto blocking and experiment with it then we could suddenly be looking at exciting charts for coldies soon but of course there is also no guarantee this signal will come to anything.

Edited by Mucka
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Posted
  • Location: South ockendon essex
  • Weather Preferences: thunderstorms and HEAVY snow
  • Location: South ockendon essex

Hi knocker/ mucka. What does HLB and MLB mean please. Ive tried searching all weather abb. sites and cant find it. Sorry mods :) thank you

Edited by snowsummer
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Posted
  • Location: Reigate, Surrey 78m asl
  • Location: Reigate, Surrey 78m asl

Hi knocker. What does HLB and MLB mean please. Ive tried searching all weather abb. sites and cant find it. Sorry mods :) thank you

If you click on HLB or MLB, it tells you :)

But it's high level blocking or mid level blocking - I think!

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Posted
  • Location: Penrith Cumbria
  • Weather Preferences: Cold, snowy winters and warm sunny summers
  • Location: Penrith Cumbria

Trends trends trends and this morning GFS has sent Uncle Barty packing for Christmas with a pattern switch to mid or high level blocking.

No cold for the UK yet although by Boxing Day Scotland could be under much colder air with snow.

It's all FI yes but it's a big switch by GFS and following the MetO MRF yesterday which made subtle but better changes to the wording of the potential cold spell I can't help thinking something is up.

In 2017 NW posters could be saying 'remember 2014 and the sudden switch in the output mid month that led to that white Christmas and the big freeze that followed'...............

I still belief in the OPI.

Andy

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Posted
  • Location: st albans
  • Location: st albans

Starting to see what follows the ens prediction of amplification to our west approaching year end. Alas (for coldies), it appears to me that mobility remains. However, the good news is that the cold shot due post Xmas should be more than just a blink and you'll miss it affair and, given it would last a few days and is scandi trough led, it should provide some precipitative interest. I would put the odds on the new year seeing us remain under the influence of a cold scandi/nw European trough/ renewed push ne of the Azores ridge at 50/50. The former option is a very interesting one for coldies, given the time of year and if mobility remains and the jet is displaced far enough to our sw, mobility would be fine as it would feed the trough with moisture.

waiting to see the ECM extended to get a feel as to whether they agree with this broad brush assessment based mainly on the gefs (and previous suites of all extended ens)

Re kris' post yesterday evening, I would love to see the vortex absent from the Canadian side but at the moment, I see no evidence that a segment will not remain into new year. We need to get that split from the parent nw Siberian though currently, I would see the two continuing to exchange their heights without strat influence to split them. it does seem that any Canadian chunk is displaced far enough away from s Greenland to allow a decent mid Atlantic ridge so not a lost cause, even if one remains.

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Posted
  • Location: Penrith Cumbria
  • Weather Preferences: Cold, snowy winters and warm sunny summers
  • Location: Penrith Cumbria

ECM not too bad either despite several days of very mild weather pre Christmas, however, Christmas Eve brings a potent north westerlies with -5c uppers reaching the west coast of the UK.

Plenty of snow north of Manchester on that +240 Christmas Eve chart!

I wonder what odds the bookies are putting on snow in Glasgow Christmas Day, might be worth a shot.

Andy

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Posted
  • Location: Camborne
  • Location: Camborne

The extended GEFS this morning is less meridional than yesterday and with less emphasis on the NE America/Greenland Atlantic ridge and eastern Pacific HP. Thus tending towards a zonal Atlantic and, to my untutored eye, no apparent indication of a major pattern change.

Charts courtesy weatherbell

post-12275-0-47541500-1418542907_thumb.p

post-12275-0-78928200-1418542915_thumb.p

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Posted
  • Location: Penrith Cumbria
  • Weather Preferences: Cold, snowy winters and warm sunny summers
  • Location: Penrith Cumbria

Not sure I agree Knocker, those charts you posted seem to indicate a noticeable Scandy through with high pressure over Canada edging into Greenland.

Or am I reading them totally wrong?

Confused mate.......

Andy

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Posted
  • Location: ipswich <east near the a14> east weather watch
  • Location: ipswich <east near the a14> east weather watch

Trends trends trends and this morning GFS has sent Uncle Barty packing for Christmas with a pattern switch to mid or high level blocking.

No cold for the UK yet although by Boxing Day Scotland could be under much colder air with snow.

It's all FI yes but it's a big switch by GFS and following the MetO MRF yesterday which made subtle but better changes to the wording of the potential cold spell I can't help thinking something is up.

In 2017 NW posters could be saying 'remember 2014 and the sudden switch in the output mid month that led to that white Christmas and the big freeze that followed'...............

I still belief in the OPI.

Andy

[agree just look deep into f1 and see what happening over  the pond deep in the freezer  on the east coast

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Posted
  • Location: Camborne
  • Location: Camborne

Not sure I agree Knocker, those charts you posted seem to indicate a noticeable Scandy through with high pressure over Canada edging into Greenland.

Or am I reading them totally wrong?

Confused mate.......

Andy

 

I would say a weakish upper trough that would indicate, to me anyway, low pressure centred NW Europe but with low pressure over at the US eastern seaboard and no Greenland blocking nothing to inhibit a westerly zonal flow. So still a fluidity in the pattern. But that's just my take on it Andy.

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Posted
  • Location: st albans
  • Location: st albans

thanks for posting the charts that fed my assessment for the end of the month knocker. not sure i read them the same way as you do though. 

 

look to our south and southwest knocker - its different to now. ecm due out shortly

Edited by bluearmy
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Posted
  • Location: Drayton, Portsmouth
  • Location: Drayton, Portsmouth

Hi knocker/ mucka. What does HLB and MLB mean please. Ive tried searching all weather abb. sites and cant find it. Sorry mods :) thank you

High Level Blocking - Higher pressure at a high latitude so i.e. at a latitude north of the UK.

Mid Level Blocking - Higher pressure at a latitude similar to that of the UK.

the emphasis being on "blocking" - doesn't need to be exceptionally strong high pressure, just enough so that low pressure systems / the jet stream can't go through it but have to go around it.

High Level Blocking is usually necessary to get Arctic air to the UK, since if positioned corrected, it can force air to travel from north to south, rather than west to east which is the norm for us when no blocking exists.

Some of this morning's charts suggest a HLB instance may occur during the Christmas week around Greenland, meaning air will have to go clockwise around the block, leading to Arctic air heading south into the Atlantic - somewhere...

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Posted
  • Location: portsmouth uk
  • Weather Preferences: extremes
  • Location: portsmouth uk

At last I have something positive to say about the output.

 

Whilst the exciting synoptics shown on the GFS might be too far W this isn't something to worry about at this stage. The GFS isn't an outlier and you can see from the Iceland ensembles that pressure is set to rise in the latter stages of the run.The GEFS control skews the mean though.

 

 

http://max.nwstatic.co.uk/ensimages/ens.20141214/00/prmslReyjavic.png

 

When it comes to blocking being shown across Greenland by the GFS I take note due to the exceptional pertormance of this model during the 2009, 2010 cold spells.

Very much agree when the gem or ecm start showing hlb then people normally think of garden path a very long garden path haha!

But the gfs has thrown this into the mix for a fair few days and it drops it and then returns back to this idea.

The gefs was the first model to show this some days ago there for there is most certain some credibility in the hlb idea.

Of coarse it's not showing a quick flip into a dickens Christmas carol style winter just yet but possible but this certainly seems to be a slow burner.

Perhaps Scrooge was visited by the ghost of Christmas past and taken back to 1963 haha but few more days and we're see where this all is heading.

But I'm optimistic for a certainly colder new year

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Posted
  • Location: chellaston, derby
  • Weather Preferences: The Actual Weather ..... not fantasy.
  • Location: chellaston, derby

. Nothing wrong with your assessment if no emphasis on mild as that is not the dominant theme.

 

 

isnt it?

 

post-2797-0-26208200-1418545632_thumb.gi a chilly couple of days, nothing too cold away from scotland

 

post-2797-0-75103500-1418545673_thumb.gi followed by three days of wet windy and mild

 

post-2797-0-95358700-1418545741_thumb.gi three days of 'average' cold before

 

post-2797-0-09425300-1418545783_thumb.gi mild mobile wet and windy weather returns throughout fi...

if the gfs 00z is anything to go by, then the cold pm incursions have been reduced in their potency, and the general trend is for more mild weather as we progress into december. now that looks pretty dominant to me ! so the 00z looks average - above average.

these arent cherry picked charts, i went through the gfs 00z and chose a chart to emphisise the ever changing outlook we have each mild/cold spell. there appears to be a tendancy here to play down milder options because its not what most appear top want. but denying their existance wont change the fact that there are milder options.

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