Model Output Discussion - The Start Of Winter

[Bristawl Si]

My feelings exactly Chiono. I was waiting to see what later runs come up with, but current runs do show the Russian HP a little closer. Once any LP over Scandinavia finally fills, now that is the time when HP can form with a vengeance. I have seen such on a number of occasions in the past. Zonal W to NW flows don't often stay as such for long, usually the cold air will win but occasionally, as hinted by the last GFS, there's a pressure build in our area as the pattern amplifies in mid-Atlantic. Cue the (sometimes quite rapid) emergence of the Scandinavian HP, pushing westwards!

It would need to push Westwards far enough to keep any Atlantic troughs at bay though wouldn't it?

Remember last Winter - am i right in saying the Russian High actually acted as the UK's 'foe', by not pushing far enough West, so keeping troughs effectively stalled right over the UK?

 

Fine margins, indeed, for this little ole island on the edge of the Atlantic.

Edited December 9, 2014 by Bristle boy

[OldMetMan]

It would need to push Westwards far enough to keep any Atlantic troughs at bay though wouldn't it?

Remember last Winter - am i right in saying the Russian High actually acted as the UK's 'foe', by not pushing far enough West, so keeping troughs effectively stalled right over the UK?

 

Fine margins, indeed, for this little ole island on the edge of the Atlantic.

Yes indeed! I can recall many winters where HP was close but not close enough to give us the full benefit of the continental flow. Ideally, we need blocking to the N as well, but one step at a time! Later runs might give us a clue as to whether this is a viable option. I shall comment in more detail later if the models warrant it!

[Barry12]

Reading some posts from the more knowledgeable folk, it does look like there could be a change during the end of December into January. Stratospheric warming continues to show during the Christmas period, and Fergie is posting some interesting stuff, in regards to Mogreps and the EC clusters. But, even without a pattern change things are still looking cold and wintry for some. Based on the GFS 06z, there will be no mild weather at all in the next 10 days with it remaining cold throughout. Snow could fall to lower almost anywhere, even the south, especially on Friday and Saturday. It does look like December will finish as a below average month..

 

 

Wednesday

 

 

Highs of 3-7C with some parts of Scotland remaining below freezing, some more snow accumulating for Scotland as well, especially over higher ground. Snow in the North even at lower levels cannot be ruled out.

 

 

Thursday

 

 

Thursday looks even colder for the North of England and Scotland, around average for the south. Many parts of Scotland won't be getting above freezing. With yet more snow for Scotland, also looking very interesting for Ireland with a high risk of snow for many parts.

 

Friday

 

 

Friday is looking very cold with highs of just 0-5C, more snow for Scotland, and possibly Northern England. Snow could fall to lower levels almost anywhere, including the south.

 

Saturday

 

 

Another very cold day with highs of 0-4C. It will feel absolutely bitter up North. A bit more snow for Scotland.

 

 

 

Given most Decembers are Atlantic dominated in the UK, this is a pretty good pattern to be stuck in. Signs are now growing of a pattern change during the end of December/start of January, so I have high hopes now of something even better developing for January for cold and snow.

Edited December 9, 2014 by Barry95

[Nick F]

 

I would say the chances of white Christmas in the South are pretty remote with Northern and Western areas best in with a shout based on the latest output and potential of brief topplers.

 

Looking further ahead with the likely SSW towards the start of January, the downwelling can take a couple of weeks or more and then a further lag before it can impact our wee islands. So perhaps a lengthy cold spell might occur from mid January onwards.

 

We don't have to wait for a SSW to occur to lock in a lengthy cold spell, tropospheric forcings alone can initiate blocking as we saw back in November, though obviously the blocking was in the wrong place for the UK to benefit.

 

The MJO looks like it may go into the COD before phases 7-8, so we may have to look other drivers, such as the emerging El Nino, favorable Atlantic SST tripole and favourable Eurasian snow cover to drive waves to hopefully change the pattern more favourably before any effects of a possible SSW in January.

 

But in the next 10 days, although no severe cold in the offing countrywide, any mild incursions look to be brief, with outlook chilly given Pm airmass will be dominant.

Edited December 9, 2014 by Nick F

[Nick L]

We don't have to wait for a SSW to occur to lock in a lengthy cold spell, tropospheric forcings alone can initiate blocking as we saw back in November, though obviously the blocking was in the wrong place for the UK to benefit.

 

The MJO looks like it may go into the COD before phases 7-8, so we may have to look other drivers, such as the emerging El Nino, favorable Atlantic SST tripole and favourable Eurasian snow cover to drive waves to hopefully change the pattern more favourably before any effects of a possible SSW in January.

 

What does COD stand for, Nick?

[Barry12]

What does COD stand for, Nick?

 

corridor of doom

Edited December 9, 2014 by Nick L

[legritter]

Well with no major cold spell visible on current modelling many of us are going to have to see what we can squeeze out of air originating from northern latitudes with the hope that good 850 mb temp and some weather systems can produce some wintryness even down to low ground .IT does look that generally the next 10 days will pan out as current Data suggests .but with the mention of christmas now coming into discussion on this forum i would say with over two weeks till 25th many things could change big time in any possible Synoptic outcome .I always try and post a more light hearted view on the charts aimed mostly at beginners and new posters ,leaving more technical views to other experienced members who are also able to post charts etc .If we take current synoptic situation over coming 5 days and go back TEN days from today what was the 10/15 day forecast certainly one of westerly systems but alas no mention realy of what we are about to experience wind wise and for some wintry wise ,so with christmas 16 days away it would take a very brave punter to say what synoptic situation we could be looking at by then .I will finish by saying plenty of action weather and all to play for Roll on tonights charts  Enjoy our weather bomb ,which was once referred to as a deep area of low pressure with a very quick drop of pressure ,im not being sarcastic just keeping up with the times cheeers gang   

[Rocheydub]

What does COD stand for, Nick?

 

 

Someone used it to term "circle of death" in a previous post showing MJO graphs i believe.*

Have to say, I know the charts usually get the Atlantic mobility patterns fairly spot on, I'm looking out my window now at trees being bent over in the strong gusts, and I'm reminded how accurate GFS and ECM were for this period.

 

*EDIT: It was I'm dreaming of on post #1243

Edited December 9, 2014 by Paul
Removed the potentially offensive bit!

[Gael_Force]

What does COD stand for, Nick?

 

I see they are calling the centre circle of the MJO charts the 'circle of doom/death' ergo COD.  You, as a met man might be able to tell me if there is an official name for it.

[Paul_1978]

corridor of doom

Circle of Doom

[Nick F]

What does COD stand for, Nick?

 

Something fishy.

 

Circle of Death

[gottolovethisweather]

The impending storm (extreme winds and heavy rain, mainly for the North) will rightly dominate the weather headlines over the coming days no doubt, but let's not take our eyes of the snow risk which could be extending South as the week progresses.

 

Take this chart for example, from the GFS non-parallel 12z run at t+66 hours showing potential for a Midlands event if timing issues correlate with the passage of any associated fronts.

 

 

 

Not a certainty for IMBY (not my back yard for now?) snow, but clearly one to watch for Midlanders and the Northern England contingent. I suspect this could yet cause a few complications to the official forecasters once the current storm has passed.

 

Whether the UKMO latest updated Fax charts agree with the above, we will have to wait and see. Alongside that, there is also the ECM 12z to consider, yet alone two more days have to pass, before the next event even comes across the mainland during Friday.

Edited December 9, 2014 by gottolovethisweather

[Nick L]

The storm (extreme winds and heavy rain, mainly for the North) will rightly dominate the weather headlines over the coming days no doubt, but let's not take our eyes of the snow risk which could be extending South as the week progresses.

 

Take this chart for example, from the GFS non-parallel 12z run at t+66 hours showing potential for a Midlands event if timing issues correlate with the passage of any associated fronts.

 

GFS 12z 091214 UK Snow risk at t+66 - 0600hrs 121214.png

 

 

Not a certainty for IMBY (not my back yard for now?) snow, but clearly one to watch for Midlanders and the Northern England contingent. I suspect this could yet cause a few complications to the official forecasters once the current storm has passed.

 

Whether the UKMO latest updated Fax charts agree with the above, we will have to wait and see. Alongside that, there is also the ECM 12z to consider, yet alone two more days have to pass, before the next event even comes across the mainland during Friday.

 

The way it develops that is rather suspect. It doesn't pick up on the developing secondary low like the more high-res models do. We'll see what the ECM says, but the 00z had pretty much no chance of snow.

Edited December 9, 2014 by Nick L

[Gavin Hannah]

For anyone worried about Xmas day snow, all I can say is 'Patience grasshopper'  One GFS run earlier had a significant Polar low and snow everywhere for Xmas then the next run flipped to southerly winds and dry weather.  As it stands, the PM airmass is giving us a taste of winter this week with most areas seeing frosts and cold temps, with snow in the north.  I would say that this winter is alreay much better that last years no show (if winter = cold and snow for you) and some of us in the south (I am now a southerner lol) could get a dusting or two this week.

 

I wouldn't be surprised to see the northern PM lows dominate going into next week also. It does appear that the HP to the south west is having a hard time making inroads and as long as we don't get blasted by a south to north Jet, I have high hopes that we could strike gold come Jan.

[LomondSnowstorm]

The way it develops that is rather suspect. It doesn't pick up on the developing secondary low like the more high-res models do. We'll see what the ECM says, but the 00z had pretty much no chance of snow.

How does the UKMO-GM look for the secondary low Nick (meteociel only gives +96 onwards for UKMO)? Interesting to have such a consistent divergence between the main models at such short range, and from an IMBY perspective the UKMO 00Z looked like it could be pretty snowy for my neck of the woods, as the warning issued this morning suggested.

[gottolovethisweather]

The way it develops that is rather suspect. It doesn't pick up on the developing secondary low like the more high-res models do. We'll see what the ECM says, but the 00z had pretty much no chance of snow.

 

Good to hear your views on this Nick, much appreciated. The following Fax Chart, albeit the UKMO 0z version stressed the complexity of situation well I thought, with many an embedded front in the mix. I'm tending to lean towards back-edge snow and generally wet stuff if the Midlands event did indeed materialise, but we'll see what develops, time will tell. Let us get the nasty 55 feet wave-producer out of the way first. 

 

 

 

One to watch for sure.

Edited December 9, 2014 by gottolovethisweather

[Nick L]

Good to hear your views on this Nick, much appreciated. The following Fax Chart, albeit the UKMO 0z version stressed the complexity of situation well I though. I'm tending to lean towards back-edge snow and generally wet stuff but we'll see what develops, time will tell. Let us get the nasty 55 feet wave producer out of the way first. 

 

UKMO 091214 0z Fax Chart t+72 - 0000 hrs 121214.gif

 

 

One to watch for sure.

 

I'll admit when I first saw the precip type on the GFS I got a little excited! The main snow threat over the next few days for low levels will be central and southern Scotland.

[Mucka]

We have a nice cold zonal flow out to day 5 with transient snow possibilities which would be very welcome even if just to see snow falling.

 

I have posted a few times about the upstream pattern and the closed low meandering around over Canada because it will directly affect whether we can squeeze any more wintriness out of the zonal pattern we are in post day 5.

Remember GFS had no upcoming cold blast for many runs with a flatter pattern as the Azores high ridged back in from the SW, this was a direct result of it phasing that closed low with the main trough (PV)

GFS finally kept the the energy separate so that low pressure slid SE and kept the pattern amplified hence our upcoming cold blast.

However that closed low remains and GFS then had it phasing with the next low and so flattening the pattern at day 5 just like it had previously for day 3 but now it is keep the energy separate again which if correct will give us a shot at squeezing some more wintriness out of the current pattern thereafter.

 

Ironically though UKMO has gone the other way today (both 00z and 12z) and phases the energy with the next low thus allowing the Azores high to ridge in and give a flatter pattern post day 5.

 

 

 

I guess it won't make a whole lot of difference if you are in the SE but for feeling cooler but it could be the difference between snow or rain from the Midlands North going into next week.

Regardless the upcoming storm and chance of some snow in the coming days are nailed on so I will hope to see some snow falling and that will keep me happy up to Christmas.

Edited December 9, 2014 by Mucka

[Mucka]

GEM keeps the cold zonal theme into next week with further snow possibilities.

 

[A.J]

For those who like to look at the longer range models for signs of possible trends, it should be noted that there has been a consistent signal in the CFS charts for a blocked January, initally Atlantic MLB, which migrates into Europe leaving us in a slack southerly feed.

 

The Euro block then degrades and it's squeezed by a developing Scandi HP & Low heights in the Mediterranean Basin leaving the UK in an easterly feed, and this pattern persists until the back end of January

 

Certainly worth keeping an eye on over the coming days and weeks to see if the mid-range models start to show this evolution

Edited December 9, 2014 by ajpoolshark

[Man With Beard]

GEM keeps the cold zonal theme into next week with further snow possibilities.

GFS not a million miles away from this. I'd say potential there for a more potent northerly than this week's - though I doubt we'd get more than two days of cold out of it. Mind you, still at D8, boy can a lot change before then, for colder or milder!

[Snowman.]

For those who like to look at the longer range models for signs of possible trends, it should be noted that there has been a consistent signal in the CFS charts for a blocked January, initally Atlantic MLB, which migrates into Europe leaving us in a slack southerly feed.

 

The Euro block then degrades and it's squeezed by a developing Scandi HP & Low heights in the Mediterranean Basin leaving the UK in an easterly feed, and this pattern persists until the back end of January

 

Certainly worth keeping an eye on over the coming days and weeks to see if the mid-range models start to show this evolution

 

The CFS as IDO has said that the theme for a blocked for Feb to April has been consistent.

[Mucka]

GFS not a million miles away from this. I'd say potential there for a more potent northerly than this week's - though I doubt we'd get more than two days of cold out of it. Mind you, still at D8, boy can a lot change before then, for colder or milder!

 

Agreed and GFS and its ensembles firming up on this idea with support from GEM. Virtually no support in GFS ensembles for UKMO so if ECM doesn't side with it either it will be interesting to see the MetO fax charts against the raw UKMO data for day 5/6 .

 

GFS 12z ensembles show the best signal yet for MLB to set up final 3rd of Dec with the first signs of an Easterly flow in the 10 to 12 day range. This may be a little optimistic but it is nice to see the signal there and I am still confident we will see a pattern change being modeled as we hit mid month (That is not the same as saying a blocking pattern will set up mid month to avoid any confusion) I am saying we will see blocking being modeled in hi res output once we hit mid month.

Edited December 9, 2014 by Mucka

[nick sussex]

How does the UKMO-GM look for the secondary low Nick (meteociel only gives +96 onwards for UKMO)? Interesting to have such a consistent divergence between the main models at such short range, and from an IMBY perspective the UKMO 00Z looked like it could be pretty snowy for my neck of the woods, as the warning issued this morning suggested.

You can see the secondary feature here over northern England:

 

 

Snow possible over higher ground and the flow slackens out temporarily north of the centre which might help with some evaporative cooling.

[Ali1977]

Interesting GEFS coming out,5 with Easterlies at day 12 along with a few Northerlies...