Winter Model Discussion - Cold Hunting -12Z 30/12/12

[fergieweather]

Ok, so.... Exeter reckon first "hints" of SSW effects in EC are already there at tail-end of next week in 00z run and subsequent shift to more meridional pattern. Game on.

[Glacier Point]

Strat profiling is very interesting... tendency to drop the main residual pv into Scandinavia !! Cold block and cyclonic for month's end ? We could well be looking at some brutal cold entering through Finland and wstern Russia / eastern Europe.

So it begins, first rapid downwell underway. Main body of the impacts at day 20 (latter part of January).

Edited January 3, 2013 by Glacier Point

[TEITS]

Strat profiling is very interesting... tendency to drop the main residual pv into Scandinavia !! Cold block and cyclonic for month's end ?

So it begins, first rapid downwell underway. Main body of the impacts at day 20 (mid to latter part of January).

Curious GP what you think of my ideas that an E,ly could well develop in the model output around the +192 timeframe? or am I just being impatient and desperate!

[AWD]

A couple of members, along with the Op, bring in colder air relatively earlier;

A clear trend to colder conditions in the 2m temps;

Edited January 3, 2013 by AWD

[Weathizard]

The 2M temps are very impressive must be less zonal cyclonic runs in there than yesterday evening. Things seem to be going in the right direction now. Let's hope there's no delays or worst of all road closures! Bad analogy alert!

ENS aren't as great as expected in FI, however, yesterday there was a BIG split around the 11'th, there seems to be a much smaller split now!

Edited January 3, 2013 by Weathizard

[The Eagle]

Mouthwatering ensembles.

http://modeles.meteo...s-0-1-264.png?6

http://modeles.meteo...s-7-1-228.png?6

Probably some even better ones but I haven't looked at them all.

There is No 17 with bitter E,lys.

http://modeles.meteo...-17-0-276.png?6

Pleasantly surprised with this mornings output. Happy to see key developments between 120hrs and 144hrs. The trough digging south out to the west was on the cards yesterday but it just never quite makes it. Upgrades coming I think.

Edited January 3, 2013 by The Eagle

[chionomaniac]

UKMO keen to move the MJO through phases 4&5 into phase 6;

Other models not so keen moving it out of phases 4&5;

GEFS similiar to the UKMO though, heading into phase 6;

AWD they are old forecasts except for GEFS. I've been waiting for them to update as I think that they could possibly lead to a quicker route through phases 4 and 5.

[chionomaniac]

Ok, so.... Exeter reckon first "hints" of SSW effects in EC are already there at tail-end of next week in 00z run and subsequent shift to more meridional pattern. Game on.

That's interesting as up to now there have been slight differences betweeen the GFS and ECM strospheric polar vortex positioning - with the ECM being the slighly less favourable of the two for as far as we can see (out to). The 06Z GFS op run is the first that I have seen that is 'in sync' with what the stratospheric forecasts have been showing. Whether or not cold will reach our shores is another matter, but it is good to see that at last the apparent disconnect between a downwelling stratospheric event and the tropospheric modelling has been overcome. I've been sitting on my hands for far too long waiting for this!

[lord stratus]

No surprises with today's upgrades, the models are trying to get a handle on how the cold weather will develop. As I mentioned yesterday the cold will arrive 15th to 18th Jan, possibly earlier.

Best chance of snow 18th jan onwards. I expect this cold spell to be notable.

[ghrud]

in case anyone missed it and due to some posts commenting on the longer range model output, some people obviously did-

fergieweather, on 03 January 2013 - 01:10 , said:

Just to re-stress a key point, as some might have overlooked it, judging by certain frustrated posts! UKMO emphasizes again (in new 6-15d briefing) how potential cold/blocked outcome from incipient SSW remains v possible but crucially how this may not be manifested within their current 10-15d forecast period. So - as others have also tried to stress - NOTHING in any NWP output in further reaches of MR should be taken with even moderate confidence! We are entering a truly fascinating & potentially rewarding period for this thread.. but it'll take time! I'm hoping to hear tomorrow how the good folk at Hadley Centre are assessing fortunes from this SSW.

Hope I'm wrong, but it seems many are pinning too much on the sudden strat warming event forcast and the possible effects it may have.

Edited January 3, 2013 by ghrud

[Jason M]

Check out the central pressure of this low from one of the ensembles

http://www.meteociel...&mode=0&carte=0

920mb core pressure of the west Coast.

Jason

Edited January 3, 2013 by Jason M

[nick sussex]

In view of Ian F's comments I find the UKMO outlook somewhat underwhelming.

No mention in the 6 to 15 dayer of anything regarding colder conditions. I would have expected some caveat highlighting at least a small chance of something colder mentioned for the latter part of that outlook.

[Snowman31]

In view of Ian F's comments I find the UKMO outlook somewhat underwhelming.

No mention in the 6 to 15 dayer of anything regarding colder conditions. I would have expected some caveat highlighting at least a small chance of something colder mentioned for the latter part of that outlook.

A bit odd , But Ian F told us what their thinking is, so it doesn't matter that much really. :-)

[Robbie Garrett]

BBC have London at -2 minimum next week in the further range. Maximums of 4*C, if it trends cooler. Looking and reading the later parts of the MetOffice forecast up till the 17th January, the following is a hint at a change but nothing exceptional.

A greater chance of frost than of late as temperatures fall to near or even a little below normal. Although drier, the south and east may see occasional cloudier periods with outbreaks of rain, the frequency of which may increase towards mid-month.

However looking at the anomalies, a cool high under clear sky due to the lack of daylight at this time of year may be responsible for the slightly cooler outlook next week/weekend.

By no means will it be exceptionally cold yet. This ECM currently shows the best prognosis we can hope from. I suspect as the MetOffice forecast says, the North/Northwest will experience quite a bit of murk.

However this high should displace towards the north west and north allowing a North/Northeasterly to come into play for the 13th on wards. I suspect looking at the GFS Ensembles for London, that with low temperatures like that showing an easterly more than a northerly is more likely. Click here to view the ensembles.

13th January onward is the area of interest, for me. Conditions probably wont be colder till the later period. Personally a very slow road into cold, probably meaning a very long road out of it.....

There is greater than average uncertainty through this forecast period, though it looks likely to start with fairly average climatological conditions, meaning the south and east of the UK will see the driest and brightest weather, while the north and west will tend to be more unsettled. However, there could be some rain at times anywhere across the UK. Temperatures will tend to often be close to average for the time of year to begin with. Then, later, there is an increasing risk of more marked changes of weather-type occurring, and the risk of spells of colder than average conditions and wintry weather increases relative to early January.

Edited January 3, 2013 by Robbie Garrett

[ghrud]

A couple of members, along with the Op, bring in colder air relatively earlier;

A clear trend to colder conditions in the 2m temps;

What area are these charts for?

[Radiating Dendrite]

What area are these charts for?

GFS ensemble charts for London.

[mountain shadow]

I'm not unduly worried about the MET update today. Things are still very much up in the air (pun intended) and it's only Thursday they will have the EC32 update overnight.

[nick sussex]

A bit odd , But Ian F told us what their thinking is, so it doesn't matter that much really. :-)

I think the inference I got was that the UKMO aren't sure the modelling is giving a true picture in the medium term.

So based on this and some of the operational runs today you'd only need some small changes to deliver cold much earlier.I understand the UKMO don't want to go out on a limb but I thought the experience they had with February 2009 would have rung some alarm bells.

Judging by their outlooks they don't see much chance of colder conditions till the back end of January even when the models have been correcting west over the last few runs probably in response to the initial reversal of zonal winds.

Perhaps MOGREPS is totally against the trends of the operationals but if not I don't really understand the lack of a suggestion of uncertainty for the latter part of the 6 to 15 dayer.

Anyway we wait to see tonights runs, if they back the pattern further west and increase the influence of high pressure to the ne with more energy digging south in the mid Atlantic then that would be interesting.

[-uksnow-]

7 sub -10 runs, an increase on yesterdays 18z's 5 (I think)

http://www.wetterzentrale.de/pics/MT8_London_ens.png

[Jason M]

I think the inference I got was that the UKMO aren't sure the modelling is giving a true picture in the medium term.

So based on this and some of the operational runs today you'd only need some small changes to deliver cold much earlier.I understand the UKMO don't want to go out on a limb but I thought the experience they had with February 2009 would have rung some alarm bells.

Judging by their outlooks they don't see much chance of colder conditions till the back end of January even when the models have been correcting west over the last few runs probably in response to the initial reversal of zonal winds.

Perhaps MOGREPS is totally against the trends of the operationals but if not I don't really understand the lack of a suggestion of uncertainty for the latter part of the 6 to 15 dayer.

Anyway we wait to see tonights runs, if they back the pattern further west and increase the influence of high pressure to the ne with more energy digging south in the mid Atlantic then that would be interesting.

No need for them to make big changes IMO. Even if things kick off earlier it wont be before say day 8/9 at the earliest, so there seems little point in making major changes today taking into account the output available. If things continue to trend positively they can always update tommorow when confidence increases slightly. I wouldnt be telling anyone to factor very cold weather into their plans just yet based on the outputs.

[ITSY]

7 sub -10 runs, an increase on yesterdays 18z's 5 (I think)

http://www.wetterzen..._London_ens.png

7 sub -10 runs, an increase on yesterdays 18z's 5 (I think)

http://www.wetterzen..._London_ens.png

Indeed, the number of runs that would deliver a snowy setup I calculated at 12, and I was being conservative, and left out the Op. An improvement on last night's 10 with no support from op.

Something is brewing, and I imagine it will chop and change in low res for the next 3-5days before we know to what extent it will affect our weather. Still no guarantees so I would say to be cautiously optimistic but be prepared for all scenarios to be thrown our way in next week.

[PubliusEnigma]

In view of Ian F's comments I find the UKMO outlook somewhat underwhelming.

No mention in the 6 to 15 dayer of anything regarding colder conditions. I would have expected some caveat highlighting at least a small chance of something colder mentioned for the latter part of that outlook.

Hi NIck,

I would suspect the UKMO consider anything beyond T144 to T172 FI. And not to be taken seriously for now. There has been a lot of discussion on here about outcomes way out in FI. This has been

shown to be very precarious perviously as we have found at our expense this winter. For now things remain unseasonably mild +13.6oC as I type..The first shoots of our Daffs are poking through the surface of

the soil I think the UKMO are keeping their options open by sitting on the fence for the latter part of January for now. What remains to be seen is what will happen to the HP to our South. If that stays nearby, mild

will never be far away.

[fergieweather]

No need for them to make big changes IMO. Even if things kick off earlier it wont be before say day 8/9 at the earliest, so there seems little point in making major changes today taking into account the output available. If things continue to trend positively they can always update tommorow when confidence increases slightly. I wouldnt be telling anyone to factor very cold weather into their plans just yet based on the outputs.

Exactly so.

[The Eagle]

Anyway we wait to see tonights runs, if they back the pattern further west and increase the influence of high pressure to the ne with more energy digging south in the mid Atlantic then that would be interesting.

TBH for the last 4 weeks we have seen run after run right across the models of endless zonal dross out to the limits of FI. Even if something significant does not come off at least things look more interesting from now on. And surprisingly the key moments are not in FI. Rather it's around that 120 to 144 time frame. Wouldn't be surprised to see big developments with the Artic High and some favors from the plunging trough in the Atlantic in the higher res parts of the next few runs. Have a feeling it's one of those situations where things could develop much more quickly. Interesting times ahead. Good timing too becuase if something is going to happen we want it as close to the core of winter as possible. A late Febuary Easterly, whilst ok and has delivered in the past, is not as good as one in January IMO.

Edited January 3, 2013 by The Eagle

[legritter]

Yes certainly looking v interesting Modell watching over coming days .if there is to be a change mid month i would have thought the modells will start to hint come this weekend .reading the information on the SSW event gives me personally a big buz ,but im keeping fingers crossed as LET downs as we all know is a big part of our hobby /interest .but over on north american forums they are getting very excited .on the later charts at the moment pressure is rising over the poles and hopefully this could creep ever closer .it wouldnt surprise me if we dont get a very cold zonal to start things off then possibly a pressure rise to our direct north ,but only a hunch ,its after this which is critical ,but as always its whats around that corner which is always a mystery .thanks to all the technical posters for some very interesting info especially the blog on THE WEATHER CENTRE FORUM ,VERY INFORMATIVE .heres hoping gang .