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Guest North Sea Snow Convection
Morning.

Yes, yesterday I thought we would be looking at a positive zonal wind forecast today so to see a further delay was unexpected. I do think GP is right and that we could be looking at something far better later in Feb. Already we have Thursday in our sights after the next couple of days!

c

The type of set up that GP has described as a manifestation of the MMW would be fantastic! It screams to me heavy convective snow showers on a NNE 'erly with a deep cold pool to our east and polar airflow tracking over a wide expanse of North Sea. Increasing solar energy would also actually work in our favour by stepping up the convection even more. Got to think Polar Lows too!

Sounds very Feb 69 to me! :D

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Posted
  • Location: Windermere 120m asl
  • Location: Windermere 120m asl

If this Stratospheric warming event makes its influence felt, lets hope it occurs mid-late Feb when winter can deliver its cruellest blow. I think the third week of Feb is when it will occur and this will bring the coldest and snoweist spell of winter thus far..

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Posted
  • Location: st albans
  • Location: st albans
If this Stratospheric warming event makes its influence felt, lets hope it occurs mid-late Feb when winter can deliver its cruellest blow. I think the third week of Feb is when it will occur and this will bring the coldest and snoweist spell of winter thus far..

doesnt want to be any later damien - 2005 saw it manifest itself last week feb and into march - despite some snow falling on consec days for two weeks, very few places had any decent lying snow. solar input melted whatever settled too quickly.

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Posted
  • Location: hertfordshire
  • Location: hertfordshire
doesnt want to be any later damien - 2005 saw it manifest itself last week feb and into march - despite some snow falling on consec days for two weeks, very few places had any decent lying snow. solar input melted whatever settled too quickly.

There was no decent cold pool to the east in 2005. If G.P. is right and i think he is spot on we could well be drawing air from a cold pool with temps of -30c at 850hpa.

Instead of max's of 2c to 3c we could be looking at max temps of -2c to -6c no problem with thawing snow there.

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Guest North Sea Snow Convection

Yes the polar easterlies continue for quite some time to come - each day forecast seens to add another day.

There is a lot of reverse zonality in the bank now - the ECM tropospheric charts in FI don't appear to jive at all with what the ECM stratospheric forecasts are suggesting. A very big negative AO must be round the corner.

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Posted
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.
  • Weather Preferences: Snow and storms
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.
Yes the polar easterlies continue for quite some time to come - each day forecast seens to add another day.

There is a lot of reverse zonality in the bank now - the ECM tropospheric charts in FI don't appear to jive at all with what the ECM stratospheric forecasts are suggesting. A very big negative AO must be round the corner.

Yes, back to the stratosphere after a very early success with all the snow today. I agree that a big negative AO is around the corner. The full effects of the MMW have yet to be felt and with the propagation still on course to have maximum effect in about a week. This could be potentially long lasting given that the reversal of winds is so prolonged.

So could the MMW helped to contribute with todays snowfall? Well the answer has to be yes. As GP has mentioned certain other factors have been favourable, notably the negative GWO phase. However, even though the MMW hasn't propagated to influence high level blocking (yet), it has had the effect of switching off an Atlantic in full flow. This can be demonstrated by looking at the mean zonal wind chart below:

post-4523-1233598798_thumb.png

The strong tropospheric polar vortex can be seen by the mass of yellow at the lower aspect of the chart. When the MMW occurs, these mean positive zonal winds drop almost immediately. It is my view that this will have been an important piece of the jigsaw that will have helped both the cold pool develop to our East and subsequent retrogression. Would this have occurred with a strong polar vortex with the increased jet strength of a week before I ask? Maybe not.

So an early benefit before the propagation takes full hold influencing the northern hemisphere's weather.

Here is hoping for a few more before the end of winter.

c

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Posted
  • Location: Edinburgh
  • Location: Edinburgh

I dont see anything in the mid-long range models suggesting sufficient enough northern blocking and polar vortex displacement to suggest a cold spell and im not sure its as simple as saying the models are struggling/haven't picked it up yet

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Posted
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.
  • Weather Preferences: Snow and storms
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.
I dont see anything in the mid-long range models suggesting sufficient enough northern blocking and polar vortex displacement to suggest a cold spell and im not sure its as simple as saying the models are struggling/haven't picked it up yet

There is no guarantee but when I look at these two NH charts I actually see a lot of potential.

post-4523-1233608419_thumb.png

post-4523-1233608432_thumb.png

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Posted
  • Location: Nantwich, Cheshire
  • Location: Nantwich, Cheshire
There is no guarantee but when I look at these two NH charts I actually see a lot of potential.

post-4523-1233608419_thumb.png

post-4523-1233608432_thumb.png

Random height rises spawning throughout northern latitudes with pressure rises lineing up north of the equator, outlook could very quickly change as polar blocking becomes more organised, in our favour we already have the scandi trough and southerly jet. Some atlantic influence should be expected as the atmosphere in my view is just starting to shuffle its cards before dealing the killer hand. CPC output this evening for 8-10 days does have similarities with that 12z, its a fine balance at the mo and way too close to call at this early stage

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Guest North Sea Snow Convection

I agree - lots of potential.

That 10 Feb chart may well have evolved that potential much further by the time we are looking at it towards the end of the week. If not for the 10th then probably not much longer after it. Keep the net weather servers well oiled and ready - this was the practice tryout :D

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Posted
  • Location: Edinburgh
  • Location: Edinburgh
I agree - lots of potential.

That 10 Feb chart may well have evolved that potential much further by the time we are looking at it towards the end of the week. If not for the 10th then probably not much longer after it. Keep the net weather servers well oiled and ready - this was the practice tryout :)

Lets hope youre right but if I had a pound for every time I read the word 'potential' on weather threads... :)

ECM looks promising this morning, what sort of things would be looking for? Vortex displacement?

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Posted
  • Location: Dorset
  • Location: Dorset

I think one of the key factors in the longer timeframe model output is the tendency for the LP's in the atlantic to not move eastwards, the latest Ecm is a good example of this and between the 11 and 12th of Feb the LP off Newfoundland goes in a NW direction or stabilises.

The first phase might be the lack of a Jet and then the building of pressure in response to this.

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Posted
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.
  • Weather Preferences: Snow and storms
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.
Lets hope youre right but if I had a pound for every time I read the word 'potential' on weather threads... :D

ECM looks promising this morning, what sort of things would be looking for? Vortex displacement?

Sometimes we all can be guilty of looking for something special in the distance and failing to notice the pot of gold at our feet.

I think one of the key factors in the longer timeframe model output is the tendency for the LP's in the atlantic to not move eastwards, the latest Ecm is a good example of this and between the 11 and 12th of Feb the LP off Newfoundland goes in a NW direction or stabilises.

The first phase might be the lack of a Jet and then the building of pressure in response to this.

That is exactly as I see it Iceberg.

With the short range synoptics looking great I think there is a lot to look forward to.

Another day with negative zonal winds!

post-4523-1233652355_thumb.png

c

Edited by chionomaniac
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Guest North Sea Snow Convection
I think one of the key factors in the longer timeframe model output is the tendency for the LP's in the atlantic to not move eastwards, the latest Ecm is a good example of this and between the 11 and 12th of Feb the LP off Newfoundland goes in a NW direction or stabilises.

The first phase might be the lack of a Jet and then the building of pressure in response to this.

Yes, I would agree with that too. Over the last few days it has been interesting watching the trend of weakening the Azores High following the end of the week northerly and steadily keeping more and more of the UK on the polar side of the jet, as the MMW signal over the pole intensifies and weakens the vortex in response to this. As the AO responds to this and goes more negative with the tropospheric effects of the MMW feeding in all the time to the output, then the charts for next week and beyond can only keep improving IMO. We are bound to see some output better than others, but that must be the trend surely as arctic heights force colder air further and further south - and the jet goes into the Meditteranean. I can see the trough over Scandinavia moving further south into europe and Siberian air coming over the top of it around mid month.

So we are getting to the time when we can really start to measure the surface effects of the MMW - which extraordinarily keeps the polar easterlies going and going!

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Guest North Sea Snow Convection
I notice the stratospheric warming event is mentioned in the Times

http://www.timesonline.co.uk/tol/news/weat...icle5645404.ece

I'm surprised at the Met Office correspondent comments, bearing in mind the MMW has yet to fully impact on the weather. Granted he does say that its effects can last for a period of weeks, but the cold easterly was not a direct effect of the MMW. Just a decrease in zonal winds ahead of it before the actual easterly reversal has kicked in.

Edited by North Sea Snow Convection
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Posted
  • Location: Orleton, 6 miles south of Ludlow
  • Location: Orleton, 6 miles south of Ludlow

Temperatures at the 30hPa level dropped slightly, but are now on the way back up again!

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Posted
  • Location: Brighton (currently)
  • Location: Brighton (currently)
I notice the stratospheric warming event is mentioned in the Times

http://www.timesonline.co.uk/tol/news/weat...icle5645404.ece

Thanks for the link Mr Data.

I also think that the effects of the stratospheric warming are not fully felt yet,

but it feels good to read in the Times about something that we've all been monitoring for weeks!

Karyo

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Posted
  • Location: hertfordshire
  • Location: hertfordshire

Once we see true heights build to the north then we will see the real cold begin. A prolonged freeze with daytime temps staying below freezing and at times well below freezing is almost definitely on the cards now i feel.

With such a warming that we had (are having) in the stratosphere you would probably have to go back to Jan 56, 63 or 47 to see a warming of similar magnitude. I could not see how you would get such sustained northern blocking without it. If this is correct then it would give us a very good idea where the weather will be taking us in the next 4 to 6 weeks.

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Posted
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.
  • Weather Preferences: Snow and storms
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.
I'm surprised at the Met Office correspondent comments, bearing in mind the MMW has yet to fully impact on the weather. Granted he does say that its effects can last for a period of weeks, but the cold easterly was not a direct effect of the MMW. Just a decrease in zonal winds ahead of it before the actual easterly reversal has kicked in.

I wouldn't put it that strongly, that the cold easterly was not a direct effect of the MMW, Tamara. I reckon that the easterly was a direct response to the MMW ( but not as a direct result of HL blocking), though one where other important factors played a part ( eg GWO phase). The strength of the MMW has already delivered negative zonal mean winds at a tropospheric level which can be seen below.

Jan 29

Jan 30

Jan 31

These may not be sustained enough to create strong high latitude blocking but will have had enough of an effect to help the easterly get off the ground. Why ever else would we have seen the stalled low pressure track in the way it did? The polar vortex has already shut up shot (maybe for the rest of winter) and the next stage is for pressure rises towards the pole as the prolonged length of the stratospheric easterlies comes into play.

Latest propagation forecast into the troposphere of the mean zonal winds looks very favourable.

http://www.geo.fu-berlin.de/en/met/ag/stra...tics/index.html

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Guest North Sea Snow Convection
I wouldn't put it that strongly, that the cold easterly was not a direct effect of the MMW, Tamara. I reckon that the easterly was a direct response to the MMW ( but not as a direct result of HL blocking), though one where other important factors played a part ( eg GWO phase). The strength of the MMW has already delivered negative zonal mean winds at a tropospheric level which can be seen below.

These may not be sustained enough to create strong high latitude blocking but will have had enough of an effect to help the easterly get off the ground. Why ever else would we have seen the stalled low pressure track in the way it did? The polar vortex has already shut up shot (maybe for the rest of winter) and the next stage is for pressure rises towards the pole as the prolonged length of the stratospheric easterlies comes into play.

Latest propagation forecast into the troposphere of the mean zonal winds looks very favourable.

http://www.geo.fu-berlin.de/en/met/ag/stra...tics/index.html

I was suggesting that the easterly was not associated with the MMW in terms of the full propagation of the MMW. That is the stance I belive we had all taken in terms of that being expected by around 10 Feb? I have as you know already documented on this thread several times that negative zonal anomalies were behind the easterly.

Probably some word semantics at play here I think which may be causing misinterpretations.

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Posted
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.
  • Weather Preferences: Snow and storms
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.
I was suggesting that the easterly was not associated with the MMW in terms of the full propagation of the MMW. That is the stance I belive we had all taken in terms of that being expected by around 10 Feb? I have as you know already documented on this thread several times that negative zonal anomalies were behind the easterly.

Probably some word semantics at play here I think which may be causing misinterpretations.

Yes, I think that I may be guilty of misunderstanding the idea of the MMW not being involved in the recent easterly. Apologies if that is the case.

Moving on, the propagation of the MMW is continuing with the zonal anomaly winds now reaching the -10m/s bracket at the tropopause. I wonder if these can propagate any lower as this often seems to be the extent of propagation from this strength of winds in most MMWs.

post-4523-1233691650_thumb.png

At the tropopause 100 hPa level the split vortex is being forecast to slowly reform back into 1 main vortex.

Here is todays profile with the two daughter vortices, one situated over Canada the other over Siberia.

post-4523-1233692150.gif

Note the area situated over Greenland where pressure is higher. This is translated further below in the troposphere, as slight pressure rises from an elongated mid Atlantic ridge stretching to Greenland, and allows the northerly airflow from a segment of the polar vortex troughing into Scandinavia.

Next T+240

post-4523-1233692449.gif

Here the reformation of 1 main vortex is forecast to occur towards the Pacific end of Siberia. This leaves an area towards Scandinavia of higher pressure at this level. I wonder if this is translated lower down then will there be the possibility of future height rises in this area to replace the present Scandinavian trough. As ever how does this fit in with other teleconnections and with GP's thoughts. I await his latest update on the GWO thread as ever with interest.

c

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