Winter Model Discussion - Cold Hunting -23/12/12

[bluearmy]

Ian, I am content to concede that residual energy near Greenland may well preclude a greeny height rise for much of jan. I am just pointing out that this does not mean we can't have heights to our ne or even due north and given the likely strat vortex configuration I would think it a reasonable solution.

[-uksnow-]

Evening everybody, hope you all had a lovely Christmas.

Anyhow, the models. 12z so far showing more amplification than the 06z, definately a good trend to follow.

06z

12z

Personally think talking about tropospheric responses to the potential SSW (or very likely near SSW) occuring in the first 3rd of jan are a bit premature, there will be much toying around of the ideas as to where the remanents of the vortex settles, whether it will be split or displaced (most likely latter according to strat thread); so lets all just take a deep breath and wait to see what the hopefully drier new year will bring us!

[IDO]

The 30 dayer hasnt changed. Its just the timescale that is altered. It will probably be adjusted on friday when the next 32 day run from ecm is issued.

I think It all depends where you sit on the strat issue. If you look at the strat forecasts then there is indeed a daughter vortex being placed close to w greenland. That is bound to drive an atlantic jet. Ecm zonal wind forecasts how a slight uptick in the lower strat as they drop out in the upper strat and the developing reversal in flow pushes residual energy downwards. a mobile outlook for week 2 is no surprise. If you ignore events in the strat completely then there is certainly a look of a strengthening trop vortex about the output. given where its been so far this winter, why would this happen? Can a trop vortex cannot exist in isolation of a strat vortex ? for low heights to sit over greenland throughout jan, i would think that would have to be the locale of either the displaced vortex post warming (unlikley given all recent strat output) or the location of the daughter vortex post warming vortex split. Assuming the latter can be correct, that would probably allow a scandi height rise as there will be a void to our ne with the other part of the split likely to be eastern siberia. The general point being that a continuation of the current strong pos NAO is unsustainable through the whole of jan. those of you who have bothered to look thru the gefs members will see as much evidence for a sustained height rise across nw europe as there is for zonality to continue.

Whilst part of the PV is west of Greenland, even if we have height's building in NW Europe, that will only possibly send us back to the two weeks ago scenario; a westerly flow blocked to our east and the UK then on the dumping ground for stuttering slow moving lows as they move west to east. That was the start of our flooding problems. I dont think any of us want that quasi-zonal pattern again, whilst waiting for that mystical easterly. I think the GFS control run is along those lines: http://modeles.meteo...s-0-1-384.png?6

A GH is what we need and I haven't seen anything other than weak heights in that area lately in the GEFS mean or individual members; with the overriding pattern of Icelandic low and AH (GEFS mean): http://modeles.meteo...21-1-384.png?6.

Edited December 26, 2012 by i'm dreaming of...

[Ian Brown]

Ian, I am content to concede that residual energy near Greenland may well preclude a greeny height rise for much of jan. I am just pointing out that this does not mean we can't have heights to our ne or even due north and given the likely strat vortex configuration I would think it a reasonable solution.

Ok let's see how it plays out, the worst situation IMO is if the Russian High appears again, can't ridge far enough West because of the low heights near Greenland and ends up beating a retreat after more weeks or lost, or worse, ends up being forced to ridge SSW and brings the wintry conditions to Italy, Greece and Turkey etc...

[cold snap]

http://www.meteociel.fr/modeles/ukmo2.php?carte=1021&ech=144&nh=1&archive=0

Much better some sort of toppler

[cooling climate]

Ok let's see how it plays out, the worst situation IMO is if the Russian High appears again, can't ridge far enough West because of the low heights near Greenland and ends up beating a retreat after more weeks or lost, or worse, ends up being forced to ridge SSW and brings the wintry conditions to Italy, Greece and Turkey etc...

You of course could very well be right but looking at the warming forcasted I am inclined to believe

that Decembers failed easterly was just a warning with a full on easterly after mid January brought

about by much greater warming and height rises to our north and northeast than what we saw in

December.

[cooling climate]

Loving the deep FI on the 12z with this mornings and this afternoons runs starting to show the first

signs of the warming filtering down into the troposphere. t384 onwards and a very cold outlook on

the cards for Europe and the UK.

[Grimsby Snow Lover]

Loving the deep FI on the 12z with this mornings and this afternoons runs starting to show the first

signs of the warming filtering down into the troposphere. t384 onwards and a very cold outlook on

the cards for Europe and the UK.

Really? Im not having a go but could you explain what gives you that impression. The run looked pretty flat in FI when I checked it. Many thanks GSL

[Summer Sun]

WSI (Weather services international) have updated there 3 monthly outlook today and they are forecasting a cold February after a mild January

[snow1975]

The PV splits into 2 in FI. One lobe moves SW from Greenland into Canada and the 2nd lobe sits over western Russia. An Arctic high develops over the Pole and wants to build SW.

Edited December 26, 2012 by snow1975

[scottishandy]

What does "amplification upstream" actually mean in layman's terms?

You need to think of the atmosphere, i.e heights at 500mb (I like to think about this as the height of a column of air at which 500mb pressure is reached, cold denser air lower, warmer air higher) as a series of waves. The taller the waves of high heights (yellow/orange) and the lower the troughs of low heights (blue/purple) the more the amplification.

Looking at the following chart the yellow to green line is quite flat from the US to UK therfore our weather and winds are very westely and relatively warm.

Compared with the following where there is a trough to the East of the US and a ridge just to our west leading to a N/NW flow which should be a bit cooler for us. This is not a great example of what we are looking for. What we want for cold is for the trough to be further W so the circulation forces warm air from the Atlantic up to Greenland giving a ridge which blocks the flow across the atlantic. We need greater amplification mid atlantic.

[bobbydog]

Really? Im not having a go but could you explain what gives you that impression. The run looked pretty flat in FI when I checked it. Many thanks GSL

probably this-

polar strat vortex obliterated!

[bluearmy]

a very interesting fi from the 12z gfs for one reason and that is the trop pattern towards the end reflects the strat pattern right up to 10hpa.

Thats the first op run to show a quick trop response to the warming. Interesting.

[cooling climate]

Really? Im not having a go but could you explain what gives you that impression. The run looked pretty flat in FI when I checked it. Many thanks GSL

The low in the Atlantic is going no further east it will be draged back into the vortex but it will

probably disrupt pulling the very cold air to the east down across the Europe and the UK.

[snowking]

The low in the Atlantic is going no further east it will be draged back into the vortex but it will

probably disrupt pulling the very cold air to the east down across the Europe and the UK.

Yep and very much follows the stratospheric forecast in the longer term with two vortices, one between Greenland/Canada, and the other through Scandinavia, with the door left open for ridging between Greenland and Scandi from the north (and in all likelihood, with the recent tendency from the Azores HP to attempt to ridge north, joining with heights from the south).

Obviously this is all still an FI forecast, but Strat and Trop looking harmonious.

We must, however, remain cautious until we get some agreement between ECM and GFS forecasts stratospherically speaking (and of course the remaining NWP from a tropospheric standpoint), and that will be some days yet

SK

[The Eagle]

Great charts if you want an ordinary winter. Not too mild, not too cold. Just average with the the odd northwesterly incursion.

For coldies it's tough going though. No sign of anything dramatic changing for the forseeable future. Interesting as well that the models now are in very good agreement right out to 144hrs as opposed to recent weeks when they were all over the place. Perhaps this is just an easier outlook to model.

[bluearmy]

We must, however, remain cautious until we get some agreement between ECM and GFS forecasts stratospherically speaking (and of course the remaining NWP from a tropospheric standpoint), and that will be some days yet

SK

You mean we've still got days and days of posters telling me winters over and its zonal mobile till 2017 ?!

[reef]

a very interesting fi from the 12z gfs for one reason and that is the trop pattern towards the end reflects the strat pattern right up to 10hpa.

Thats the first op run to show a quick trop response to the warming. Interesting.

Its a dire run for anything cold though, with the Bartlett securely in place for almost the entire run:

T+36:

http://www.wetterzentrale.de/pics/Rtavn361.png

T+96:

http://www.wetterzentrale.de/pics/Rtavn961.png

After the briefest of ridges, its back again at T+240:

http://www.wetterzentrale.de/pics/Rtavn2401.png

T+324:

http://www.wetterzentrale.de/pics/Rtavn3241.png

Its about as poor as you can get*. The simple fact that people are now talking about mid-Jan and February says it all really!

*or as good as it can get if you like mild, wet and windy of course!

[Ian Brown]

Its a dire run for anything cold though, with the Bartlett securely in place for almost the entire run:

T+36:

http://www.wetterzen...cs/Rtavn361.png

T+96:

http://www.wetterzen...cs/Rtavn961.png

After the briefest of ridges, its back again at T+240:

http://www.wetterzen...s/Rtavn2401.png

T+324:

http://www.wetterzen...s/Rtavn3241.png

Its about as poor as you can get*. The simple fact that people are now talking about mid-Jan and February says it all really!

*or as good as it can get if you like mild, wet and windy of course!

Yes I think that run is the lowest point thus far this winter. I don't think we are realistically going to see anything indicating a change for some time in the NWP.

[High Altitude]

If and it's a big if, but if the winter fails to get going then this will teach me to view the background signals as more of a generic guide to the northern hemisphere pattern rather than a green light for guaranteed arctic excursions to our little island.

Edited December 26, 2012 by High Altitude

[bluearmy]

I thought yesterday's runs were the lowest point? It seems some virtues are rather lacking on this thread (patience being the main one).

The bartlett (if you're determined to refer to it as such) is 'zonal' in high res as we get cut off troughs dropping into europe. I can think of runs which could look a lot worse than this one.

[Summer Sun]

GFS continues to be positive for the flood hit areas with high pressure now looking fairly likely after this weekend deep low passes through uncle Bartlett pays us a visit

Not saying winters over but its on hold for the foreseeable future again tonight I think it will be mid January at the earliest before it arrrives maybe even like last winter it will arrive in February I can't remember the last really cold and snowy February lasting more than 10 days

[Weathizard]

People writing things off because of T300+ charts? Really? The strat looking great, patience is needed by some I feel, not even through december yet to say things are over I feel are quite frankly stupid.

[TEITS]

Lets just cut to the chase because their is nobody who is usually more optimistic than me and often I have the patience of a saint. However we cannot gloss over what is a very poor outlook.

At this stage many have not seen a snowflake so far this winter and based on the current model output we might have to wait until mid Jan at the earliest. Looking at the 12Z GEFS mean and its spot the difference between the +240 & +384 charts.

[latitude]

People writing things off because of T300+ charts? Really? The strat looking great, patience is needed by some I feel, not even through december yet to say things are over I feel are quite frankly stupid.

So the strat looks great......that means nothing for cold for the UK....just one factor that could help bring cold to the UK.