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J10

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I might be wrong, but didn't the polar low in Dec 2000 which affected Western areas come on the back of a NE'ly flow?

I am actually beginning to suspect that was a shortwave rather than a polar low. The more I look at it the less like a polar low the late Dec Scotland/N.I. snowfall was. The synoptic set-up is moving towards a very similar picture between now and then though. Seductively similar :D:)

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Posted
  • Location: Newcastle upon Tyne
  • Weather Preferences: Thunderstorms and heat, North Sea snow
  • Location: Newcastle upon Tyne

Can someone explain what a polar low is please and why it appears to be such an exciting phenomenon?

I believe they are quite intense and can be associated with large precipitation totals (snow). They have been called Arctic Hurricanes before as well. The last one in the UK was in early March 2006 dumping 30-50cm across NE Scotland I believe, mostly 30cm.

I think there is an entry in the Netweather Guides by a more knowledgeable member than myself, but I can't remember where it is. :D

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Posted
  • Location: St Albans, 95m asl
  • Location: St Albans, 95m asl

I know we're all very keen to see what happens into next week. However again the GFS indicates snow showers for E areas tomorrow.

http://www.wetterzentrale.de/pics/Rtavn304.png

During Friday it looks as though a trough is going to push S from the NE.

http://www.wetterzentrale.de/pics/Rtavn424.png

I always find these little features are illustrated well on the vortical lift charts:

http://www.wetterzentrale.de/pics/Rmgfs307.gif

http://www.wetterzentrale.de/pics/Rmgfs337.gif

http://www.wetterzentrale.de/pics/Rmgfs367.gif

Not anything massively heavy but clearly a little feature shown there, with a much heavier feature (again most likely a trough) just coming into NE'ern areas on the last chart - that tracks directly south

SK

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Posted
  • Location: Lincoln, Lincolnshire
  • Weather Preferences: Sunshine, convective precipitation, snow, thunderstorms, "episodic" months.
  • Location: Lincoln, Lincolnshire

I am actually beginning to suspect that was a shortwave rather than a polar low. The more I look at it the less like a polar low the late Dec Scotland/N.I. snowfall was. The synoptic set-up is moving towards a very similar picture between now and then though. Seductively similar :D:)

Nope- there were a few articles on the 27th/28th December 2000 low pressure system in the Weather journal which confirmed that it was indeed a polar low. What we're seeing for Saturday is definitely a shortwave.

I think the GFS is having real problems handling this cold spell at the moment, and so although I think its outputs are quite useful for up to 3 days out in determining temperatures and likely shower distribution, for the longer term I suggest reading rather more into what ECM and UKMO are showing. Although GFS briefly came out on top for Northern Hemisphere accuracy a while ago (around 21 December if I remember rightly) it has since plummeted alarmingly according to the latest model accuracy plots.

The sinking of the high at T+168 and complete mess over Greenland looks somewhat implausible. Normally if a high sinks like that it's accompanied by low pressure coming over the top.

Edited by Thundery wintry showers
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Posted
  • Location: Kemnay, Aberdeenshire AB51 - 135m/440ft asl
  • Location: Kemnay, Aberdeenshire AB51 - 135m/440ft asl

As far as I know Polar Lows generally don't originate from the NE. They usually track long distances from direct north? They do sometimes crop up without being expected by the run of the mill models.

AS far I can remember the last one did form from the NE just about where that low is now, but it was spurred into action by a northerly/arctic flow running along side it, as in the low fed into the colder stream? (PS that is just my take as I was lucky enough to be radar watching that night)

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Posted
  • Location: Peterborough N.Cambridgeshire
  • Location: Peterborough N.Cambridgeshire

Can someone explain what a polar low is please and why it appears to be such an exciting phenomenon?

http://en.wikipedia.org/wiki/Polar_low

My parents often talk about a snow event due to a Polar Low. This hit the E Midlands on Feb 1969. They always refer to the sheer intensity of the snowfall.

Back to the 18Z and blimey this is progressive. So far today the GFS runs have been very different and its this inconsistency I dislike.

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Posted
  • Location: Nuneaton,Warks. 128m asl
  • Weather Preferences: Snow then clear and frosty.
  • Location: Nuneaton,Warks. 128m asl

We may be underestimating the potential for even inland snow as this feature tracks south,

fax60s.gif

With those fronts there is a chance of a band of snow in the flow perhaps.

It may only be a sprinkling inland but it`s still developing so it`s something to watch.

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Posted
  • Location: Waltham Abbey, West Essex 144ft a.s.l.
  • Weather Preferences: snow, thunderstorms
  • Location: Waltham Abbey, West Essex 144ft a.s.l.

Has the pub runstarted coming out yet? :D

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Nope- there were a few articles on the 27th/28th December 2000 low pressure system in the Weather journal which confirmed that it was indeed a polar low.

Glad to hear it! Just that the feature when viewed on the chart archives has all the appearances of a shortwave, thank you for confirming otherwise.

Can it then be said that there is an outside chance of this happening again with the current synoptics?

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Posted
  • Location: Bolton, Lancashire
  • Location: Bolton, Lancashire

I'd have thought thats quite possible, as well as the Kent streamer, that should set-up further east this time round as the flow looks a bit more northerly then last time.

Anyway IMO the most plauseable solution right now is a E/NE/N airflow till about the 9-11th, then high pressure to slowly build over the UK...after that much depends on the exact location of the PV, we want it to get shunted towards Eastern Canada, with a block in place already the southerly jet could try to undercut the high and even if that doesn't happen any shortwaves on the eastern part of the high should keep heights quite close to the UK...

Good evening Kold..

If i'm wrong the model charts before Christmas had the same set up for a wash streamer, winds ENE backing NE

Gave us in Northants very heavy snowfall.

Not a great wash streamer but it happend.

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Posted
  • Location: Upton, Wirral (44m ASL)
  • Location: Upton, Wirral (44m ASL)

We may be underestimating the potential for even inland snow as this feature tracks south,

With those fronts there is a chance of a band of snow in the flow perhaps.

It may only be a sprinkling inland but it`s still developing so it`s something to watch.

I think it's down to how much moisture it can pick up from the North Sea before the fronts cross Scotland. Also how much of that moisture is deposited over the Scottish highlands will determine what is left for areas to the south.

As TWS mentioned earlier, I believe the greater potential is for coastal shower activity as that trough moves south and temporarily modifies the flow direction.

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Posted
  • Location: Carlisle, Cumbria
  • Weather Preferences: Atlantic storms, severe gales, blowing snow and frost :)
  • Location: Carlisle, Cumbria

We may be underestimating the potential for even inland snow as this feature tracks south,

fax60s.gif

With those fronts there is a chance of a band of snow in the flow perhaps.

It may only be a sprinkling inland but it`s still developing so it`s something to watch.

i hope there is no warm sectors in this as normally there is and we get rain event!!

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Posted
  • Location: Eastbourne and Larnaca,Cyprus .
  • Location: Eastbourne and Larnaca,Cyprus .

You do have to laugh at the gfs ability to go from one extreme to another between its different runs, at 240 hrs the gfs 12hrs had a greenland high and this time the PV is up there on the gfs 18hrs. Anyway regardless of the gfs's behaviour it's been a very good evening in the model output.

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Posted
  • Location: south london, sutton
  • Location: south london, sutton

We may be underestimating the potential for even inland snow as this feature tracks south,

fax60s.gif

With those fronts there is a chance of a band of snow in the flow perhaps.

It may only be a sprinkling inland but it`s still developing so it`s something to watch.

the most amazing thing about that fax is that you can see just how far south the jet stream is , look at all those lows queing up in the atlantic and heading towards Spain

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Posted
  • Location: st albans
  • Location: st albans

sorry, but in the context of the 12z NAEFS ens, the evolution of the 18z isnt possible. as darren says, far too progressive.

Nick S, i note that the NOAA discussion tonight talks about the upstream pattern getting a shove eastwards. given the canadian/greenland ridge holding reasonably firm, this will have the effect of pushing the atlantic trough ne towards us and increasing the chance of a snowy breakdown from the sw.

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Posted
  • Location: Lincoln, Lincolnshire
  • Weather Preferences: Sunshine, convective precipitation, snow, thunderstorms, "episodic" months.
  • Location: Lincoln, Lincolnshire

Glad to hear it! Just that the feature when viewed on the chart archives has all the appearances of a shortwave, thank you for confirming otherwise.

Can it then be said that there is an outside chance of this happening again with the current synoptics?

I think there's an outside chance of a polar low forming if we get a subsequent northerly around 5 January as is shown on the models- particularly if it starts off as more of a direct northerly rather than being north-easterly from the word "go".

On Saturday a polar low is very unlikely but you may get some kind of trough develop in conjunction with the shortwave to produce more organised snowfalls out west in the Irish Sea- again something worth monitoring.

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Posted
  • Location: Waltham Abbey, West Essex 144ft a.s.l.
  • Weather Preferences: snow, thunderstorms
  • Location: Waltham Abbey, West Essex 144ft a.s.l.

I think it's down to how much moisture it can pick up from the North Sea before the fronts cross Scotland. Also how much of that moisture is deposited over the Scottish highlands will determine what is left for areas to the south.

As TWS mentioned earlier, I believe the greater potential is for coastal shower activity as that trough moves south and temporarily modifies the flow direction.

I agree its def going to be shower activity the main focus for eastern half of the UK. Hopefully they will penertrate well inland, also chance of the channel low for southern half of the country.

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Posted
  • Location: Upton, Wirral (44m ASL)
  • Location: Upton, Wirral (44m ASL)

the most amazing thing about that fax is that you can see just how far south the jet stream is , look at all those lows queing up in the atlantic and heading towards Spain

Yes! You can see that effect really well on the sat24 animation as well. Our current "lazy" low has been sat piddling about off SW Ireland for 48 hours and systems have been hurtling past below it headed for southern Europe.

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Posted
  • Location: Liphook
  • Location: Liphook

The sinking of the high at T+168 and complete mess over Greenland looks somewhat implausible. Normally if a high sinks like that it's accompanied by low pressure coming over the top.

See I think its quite possible BUT way too fast...the reason for this is because the PV itself is what dictates the change. The 18z flips the AO back towards positive and as a result the upper high actually is forced southwards...however at the same time we still have a undercutting jet stream so the high sort of gets forced to stay between 45-55N, its the sort of set-up that could lead to a rather prolonged HP set-up, as well as a cold flow.

Of course I suspect the models are rather overprogressive with the evolution as they usually are as such extreme -ve AO bouts don't usually flip over the space of 2-3 days like the GFS is trying to have us believe.

Saying that there are many types of evolutions that could evolve once the PV finally does start to get its act together again...

Edited by kold weather
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Posted
  • Location: Hull
  • Location: Hull

We may be underestimating the potential for even inland snow as this feature tracks south,

fax60s.gif

With those fronts there is a chance of a band of snow in the flow perhaps.

It may only be a sprinkling inland but it`s still developing so it`s something to watch.

My only worry with that, is the increasing dew points due to the warm sector on the LP, probably nothing, as this 18z is messy, progressive and packed full of shortwaves.

Lewis

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Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

regarding Polar Lows-they are usually fairly obvious and are picked out by the models but there is a tendency amongst some posters to see them when they are not there!

this NW Guide gives a reasonable idea of what they are and also links to some other reading which may help those new to the fascinating www world of meteorology.

http://forum.netweather.tv/topic/21629-the-polar-low/

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Posted
  • Location: Eastbourne and Larnaca,Cyprus .
  • Location: Eastbourne and Larnaca,Cyprus .

sorry, but in the context of the 12z NAEFS ens, the evolution of the 18z isnt possible. as darren says, far too progressive.

Nick S, i note that the NOAA discussion tonight talks about the upstream pattern getting a shove eastwards. given the canadian/greenland ridge holding reasonably firm, this will have the effect of pushing the atlantic trough ne towards us and increasing the chance of a snowy breakdown from the sw.

Well the good point about that is that it reduces the chance of a western based negative NAO which is always frustrating and at least any angle of attack will be favourable, however i'm not convinced of any possible attack apart from the very uncertain possible event for early next week, basically we want the southern arm of the jet to remain as flat as possible, so we could make a case for the greenie high weakening but the jet still being favourable enough to keep the uk in a cold pattern.

I'm still thinking that perhaps we might see the ridge toppling ne' wards towards Scandi, and if this does happen and with the PV remaining disorganised this might be a case of waiting for another reload with the PV disrupting again and the high eventually backing nw with trough developing over Scandi and further WAA in the west Atlantic bringing back our friend the Greenland high. Anyway theres loads of weather to get through before then. At the moment it's hard to say where the pattern could eventually end up, often in recent winters you think when one door closes it's going to remain shut but this time perhaps we'll have a couple of keys up our sleeve! :)

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