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

[Peter H]

Interesting to see more cold weather solutions in the models. Over the coming weeks it is going to be fascinating watching how they show the changes and keeping a close eye on the Stratospheric Warming, it is going to be far from boring for any avid weather watcher. I got to feeling it is going to be a slow progress to any cold over the coming weeks, but then it will pick up and before we know it shall arrive on our shores, that is a hunch btw. A very special winter event is beginning to brew :-) Enjoy the ride!

I dunno what everyone else is looking at, but I can't see anything special for the next two weeks, right up until the 18th.

Dream on

[AWD]

Looks like the MJO could be heading through phases 4 & 5 and into a weak phase 6 over the next couple of weeks;

With the CPC analog composite showing a broadly similiar pattern to what we've been used to around the UK, with troughing to the west, and heights to the south. There are increased heights apparent over the pole however;

PNA going slightly negative;

NAO & AO near neutral;

All signals, which with my basic understanding, would help aid any stratospheric warming that may happen, including those more specifically after the initial SSW. A shift of the MJO through to phases 7 & 8 would be nice though.

It's the above, rather than the NWP output, I feel we should be monitoring more with regards to later on this month & into February. The NWP output will have a difficult time finding locations of any blocking until the warming's propagate down into the 500mb heights, therefore looking at the above forecasts, these drivers will help aid and work with the stratospheric warming's, and locate favourable places for HLB.

Reading it back, this post hasn't come out like I had hoped, however I'm knackered & off to bed, make of it what you can, but the main gist is very interesting times ahead with complex forecasting scenarios stretching even the most experienced forecaster.

Edited January 3, 2013 by AWD

[Bonjangle]

MODS delete if this aint allowed ,but been watching Western parts of Finland and IMO i have not seen cover and cold like this at this time of year for a very long time http://www2.liikennevirasto.fi/alk/english/kelikamerat/kamera-C0250402.html further North yes but not on the West coast .

[AWD]

Also of note is that the EC extended ens beginning to show a "split" in the extended output, with a cluster showing some colder solutions now;

It's been a couple of days since I last viewed them, but these are showing better colder scenarios compared to the last ones I viewed IIRC.

[fergieweather]

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.

[joggs]

Cheers Fergieweather, keep us updated. Regards

[Timmytour]

Grim

Dark Dank and Drizzly in Durham?

Ian

Refreshing to see someone assess the outcome of a day as opposed to a season on one chart!

In the meantime I think its a commendable chart that provides the UK with a mild days that's akin to those in mid Jan 1947.

If that's what it takes to get there....

Look at what the 0z from friday morning starts showing.....that will be the establishing, if not the beginning, of an exciting model AND weather journey!

[LomondSnowstorm]

I must say I like how the pub run and now the 00Z GFS is developing the energy in the Atlantic at +144, nice looking trough angle and generally everything again quite a lot further west than 24 hours ago:

Details not so important but the trend of getting more WAA to our north is a very helpful one in the medium term.

Edited January 3, 2013 by LomondSnowstorm

[Staffordshire]

I must say I like how the pub run and now the 00Z GFS is developing the energy in the Atlantic at +144, nice looking trough angle and generally everything again quite a lot further west than 24 hours ago:

Details not so important but the trend of getting more WAA to our north is a very helpful one in the medium term.

yes definately getting the pattern westwards in these past couple runs! blimey first 0z ive been awake for in ages - cant sleep

[LomondSnowstorm]

yes definately getting the pattern westwards in these past couple runs! blimey first 0z ive been awake for in ages - cant sleep

Haha, I've been up for quite a few lately, combination of student sleeping patterns and being on holiday. Anyway, UKMO 00Z continues this, lots of trough disruption, a bit too many shortwaves around Iceland for my liking but the Atlantic 'plunge' can only be a good sign.

[The PIT]

If this carries on we will be able to look for the first signs of spring in a couple of weeks. Another poor GFS run hopefully the ECM will show something better.

[Gustywind]

Ensembles better this morning though on GFS, op run one of the milder runs, control run looks cold in FI.

Large number of sub -5 runs now in ensembles, even for London.

Think some posters are far too quick to give up hope this winter, I'm expecting a mild jan overall (very mild first half, cooler 2nd half), but do expect a decent cold spell at some stage in late jan, early feb, possibly a bit earlier.

[Snowmad79]

It's all if and buts lately. The chart above, had the LP south of Greenland had been shown to stall further west we could of seen decent ridging with much much better WWA into Greenland, Plumping up High Pressure of Over Greenland, Svalbard. There is at least a slim possibility of getting this around the 10th Jan onwards! For me personally, its the first run I've seen myself where low pressure has been removed from that vacinity in favour of HP and slightly improved ridging.

You can tell that is an attempt at ridging towards GL as the aforementioned LP is rolled back on itself.

Edited January 3, 2013 by Snowmad79

[snow drift]

Lets put the GFS aside, thats not the issue, you know my thoughts on the GFS FI, the ECM has had all manner of synoptics, we've had troughing to the north, ridge over the UK between low heights either side, we've had a continental flow with an elongated high, we've had a pool of colder uppers being advected sw.

All I can go on is having looked at thousands of model outputs at that range, the pressure pattern to the north of the UK at the 216hrs timeframe looks so unlikely to occur that I fully expect it to disappear by tomorrow morning.

After an interesting discussion between two well respected posters, this is the result. These conversations/ discussions aide my learning. It also shows to many that you can have a disagreement without being rude and insulting. By the way, have a look at the ens, they are heading down with some interesting ones to say the least.

[bluearmy]

we may have passed the 'tipping point' wrt to the gefs. Lets see what the 06z and 12z spew out but deinitely trending down a cold route now. greeny, icelandic or scandi! where will the blocking be centred? It may not be that impressive in which case the pfj will slowly sink across us (messy).

Edited January 3, 2013 by bluearmy

[Jason M]

Again, the opps are not fantastic at face value, but there are some really exciting ensembles this morning. The number of jaw droppingly good ensemble members has increased and whilst you can't read too much into ensemble runs the good uns are starting to show similar Synoptics. Where as the December charts were showing easterlies but via completely different routes some of the ensemble runs are starting to show 'the same' easterly.

Another point of interest is that the good stuff is not all out at the extremes of FI. A couple of days ago everything was at 300 hours plus. Not now though.

Jason

[Ian Brown]

Well the charts this morning are not without interest, both the GFS and the ECM raise pressure to the North at day 7 and we see a cutting of the link of the jet between Greenland and Norway, which has to be a good sign.

We still have the benign HP to the South and the jet not really knowing where to go, but if your glass is half full then there is definite interest going forward from the ECM T240.

[IDO]

Although there are clear signs that the HLB is beginning to take shape on the GFS, I am still concerned that the PV piece over West then SW Greenland will prove poor in terms of prolonged cold for the UK:

As the above charts (t384) show, the jet is pumped up from the energy from the PV and strengthens the jetstream. Although in this frame we are influenced by a trough, this looks like it will be flattened by the jet quickly, preventing any sustained cold. That PV prevents any ridging in the west Atlantic, thus sustaining the relative westerly flow.

Things can change and will, but getting rid of that PV piece would give me greater confidence in the medium/long term potential.

ECM more progressive with the northern blocking:

However, again with the PV where it is, the UK is left in a mild sector, whilst severe cold invades continental Europe. Copenhagen (only 4 degrees further north than London), for instance their ensembles:

That was what I was hoping to see for the UK around now. Severe cold showing up, quickly.

So we have cold on its way, now we will see where that goes compared to the UK.

Edited January 3, 2013 by i'm dreaming of...

[Tom Montalbano]

Well the charts this morning are not without interest, both the GFS and the ECM raise pressure to the North at day 7 and we see a cutting of the link of the jet between Greenland and Norway, which has to be a good sign.

We still have the benign HP to the South and the jet not really knowing where to go, but if your glass is half full then there is definite interest going forward from the ECM T240.

Yes as Ian states, plenty of interest from the overnight runs with more of a trend to blocking out at day10, long way off of course but we seem to be heading in that general direction now.

As Ian Fergie stated earlier, some members have been getting a bit ahead of themselves expecting blocking to be in place with attendant raging easterlys by the 15th, don't think that was really expected to happen by the mid-point of the month.

I'll leave you with the t240 ECM 00z chart, a long way off still but if verifying would take that now.

http://www.wetterzen...cs/Recm2401.gif

That kind of synoptic evolution in the past has been a precursor to some notable cold spells and IF we get to that point MAY well be looking at the beginning of some wintry weather reaching our shores some 5 days or so later, which of course is right at the end of the METs 6-15 day update.

More patience required I feel. As John H, TEITS,stated a few days ago, amongst others, expect to see more and more blocking scenarios to develop in the model runs by the week-end.

Regards,

Tom

Edited January 3, 2013 by TomSE20

[Gibby]

Good morning. Here is a look at the 00z output from GFS, UKMO, GEM and ECM for today Thursday January 3rd 2013.

All models show High pressure close to Southern Britain with a broad and moist Westerly flow over the UK carrying a lot of cloud and some drizzle to west facing coasts and hills. Little change is expected over the coming few days as the basic setup as now remains in place. Early next week a weak trough does move East bringing some rain acoss from the West on Monday or Tuesday and again on Thursday with the remainder of the week seeing High pressure remain relatively close to the South with any rainfall restricted to more Northern parts as Low pressure to the North continues to push troughs East over the North at times.

GFS then through FI shows similar conditions for a while before a Southerly flow freshens due to a more meaningful depression in the Atlantic. This spreads cloud and rain across all areas later with all areas becoming unsettled and chillier by the end of the run with rain at times and snow possible on Northern hills. After a very mild start to the run temperatures gradually fall back to more average conditions later.

The GFS Ensembles show that the operational was on the milder side of the pack in the second half of the run with the majority showing cooling rather more prominent to levels slightly below the seasonal normal with the control run taking us into the freezer in the final week. Rainfall amounts do increase somehat in Week 2 but there remains quite a lot of dry weather shown in most places.

The Jet Stream shows a continuation of the flow arching over the UK in response to High pressure close to the South of Britain before it slips further South in a very much weakened state towards the end of next week.

UKMO for midnight on Wednesday shows the trough that crossed East on Tuesday having moved away East returning the UK into dry and settled conditions again as High pressure re-establishes itself close to Southern Britain with dry and fine weather in temperatures well up to normal.

GEM shows a High pressure cell drifting slowly East from Southern Britain to Europe as a light Southerly flow develops with some bright or sunny spells and the chance of some overnight frost and fog patches developing overnight.

ECM shows a trough moving East on Thursday with some rain for many for a while before a return to High pressure conditions develop as height's to the South of Britain remain in place. Temperatures remain very much up to normal or above at Day 10.

In Summary this morning the UK weather will be dominated with High pressure to the South or East of the UK for the next 10-14 days. This means there will be a lot of dry weather around, especially in the South. There will be some rain at times in the North and this may filter South and East at times. Temperatures will be on the mild side especially early in the period before temperatures decline to levels nearer to the seasonal normal during the second half of the run.

[Summer Sun]

Compared to the rain we had last year the GFS ensembles remain fairly dry for the south

[TEITS]

Very pleased with this mornings trend but again its too early to have much confidence in the eventual outcome but the trend is tipping in our favour.

A clear split is developing in the ensembles from around the 11th Jan onwards.

http://cdn.nwstatic.co.uk/ensimages/ens.20130103/00/t850Cambridgeshire.png

Now if you look at how many cold runs their are then you can see how the trend is tipping in our favour. Only a few days ago the GEFS runs only had around 1 or 2 members below -5C.

This trend is shown on the Iceland SLP mean because this has now increased to 1008mb.

http://cdn.nwstatic.co.uk/ensimages/ens.20130103/00/prmslReyjavic.png

If you remember I was concerned of a strongly positive NAO but using the basic measurement of the SLP at Lisbon, Reyjavic then im becoming less concerned. Whilst these means don't suggest a negative NAO they are trending in the right direction.

http://cdn.nwstatic.co.uk/ensimages/ens.20130103/00/prmslLisbon.png

So taking on board all of the output then in my opinion a cold spell could develop within the +192/+216 timeframe. At this stage this is more likely to come from the E via a developing HP around the Scandi/Iceland region. At this stage I doubt it will be a GH, that might come later!

[Duane S.]

Continuing interest in this mornings charts. Some very cold GEFS ens popping up over the past couple days and the 00z is certainly no exception!

That said I can certainly see why Ian F is hinting that we MAY have to wait a little bit longer than most of us would want.

I've tried to pick out trends on the outputs. It'll change no doubt but the mean view seems to be N Pacific high ridging, bolstering heights @ the pole in turn this should help pull away the vortex away from Greenland into Canada but as has been the case all winter it wants to leave one of its mates behind! Question is, is he our friend or foe? This is where the ECM raises my eyebrows at +240 with favourable ridging appearing North of Scandi. I hope I'm wrong but IMO we need one last member of the cavalry to help get things snowballing from that point. The MJO looks to be of little help as is heading off to sun itself in Thailand for a while. That area in known to be poorly modeled relative to other areas so one to watch over the coming days and it may still arrive in a more favourable phase just in time anyway.

Still, I remain extremely excited by the prospect of the next month or so of model viewing as I am convinced we will get a cold spell out of this but I just can't see anything before the middle of the month at the earliest. Yet!

[Summer Sun]

The Beijing climate centre model updated at the end of 2012 and what it shows is temperatures above normal for the period of January to March

It also shows rain is likely to be of average amounts for England and Wales with above normal amounts for Scotland and Northern Ireland

[UV-RAY]

The Beijing climate centre model updated at the end of 2012 and what it shows is temperatures above normal for the period of January to March

It also shows rain is likely to be of average amounts for England and Wales with above normal amounts for Scotland and Northern Ireland

Another unfavourable update for cold, still we have to hope that all LRF models are barking up the wrong tree.