[Wales/Cymru Regional Weather Discussion]

Andy, I may need to speak soon about backing tracks, My 9yr old plays guitar

He sings and plays Wonderwall and Don't look back in anger

Few others but big one's are  also dead or Alive - Bon Jovi and Paint it black by the stones

 

[Wales/Cymru Regional Weather Discussion]

oops posted this in the main thread i will be done over for that

those wondering about tonight

here are current and predicted radar and Cardiff looks goos around 11:30

http://www.floodwarn.co.uk/live snow reports snowing now.htm

[Model output discussion - the beast arrives]

those wondering about tonight

here are current and predicted radar and Cardiff looks goos around 11:30

http://www.floodwarn.co.uk/live snow reports snowing now.htm

[Wales/Cymru Regional Weather Discussion]

Just a clear up about yellow warning for tomorrow

That warning is just where snow may be enough to cause some minor issues, its not suggesting Cardiff for instance, will not see any snow. They currently see it as lighter in cardiff.

We have warnings when rain is heavy enough to cause issues, but that does not mean others will not get rain

[Wales/Cymru Regional Weather Discussion]

Dry east winds have made grass dry and so grass fires have started today, Blackening our hills and killing wildlife, i suspect that is what the fire/smoke is, hopefully a bit of snow overnight and tomorrow will stop that happening. Still looks good Thursday and Friday

[Model output discussion - here comes the beast!]

Meteogroup use all models including the met office models , GFS and ECM

The Met office also used to look at GFS and would consider its out put.

 Everything we see and more is being viewed, like us the main forecaster will make a call based on likelihood mainly using the consistence between models and different runs. They do of course have the luxury of very high resolution Met  models  too.

Details between the main models tonight are pretty similar, small details  on snow, where and how much will be 24 hours out for most, but i think the East coast can start celebrating now. Further West IMBY i thinks its very likely that snow will occur and its just slight changes that will decide exactly when. This looks more like 1987 to me, but what ever the final outcome i would suggest all models indicate , that for a change elevation and M4 are not going to be the issues they normally are for settled snow. Hope you all get something.

[Model output discussion - here comes the beast!]

The models have all done well with this, At the timeframes we have been watching until now its been about picking up the trends. To some extent that remains too. The trend we are looking for is placement of the high and orientation to see if we get very cold or extreme cold.

I have not posted since last week because as i said then the models will vary a little on the exact  picture, but it would be the small details. It has always and remained a cold outlook.  The most important updates away from the models we see, are met office. The BBC has Meteogroup who use all models (The Met Office do use all too) and so we can see that they have been calling this much the same as many posters on here.

What the models are showing, in regards to snow, is

South East Coast look to be the first and most at risk to see snow, with a good covering by Monday next week, that risk moves to include east Coast further North by Tuesday. Central- southern England likely to see snow showers as the week progresses and for all dew points and 2m temperatures will allow settled snow at all levels.

East Wales may see flurries and light snow showers as we head towards mid week, As may the Southwest of England

Likelihood of some significant snow is just about anywhere beyond that, no model will be accurate at that timeframe and so we just wait to see how things develop. I would suggest looking at all models that South east and some Southern Counties of England will have enough by then to close some schools quite widely ( It does not take a lot to do that) 

I do think at times people look for too much intimate detail rather than the trends, this trend has been in place since 6th February and my initial forecast has not changed since then. MJO and SSW indicated this pattern perfectly.

The only huge changes i force will be for individual IMBY stuff which may change run to run and then be different on the actual day.

ICON has been surprising consistent but in general the models have all been very consistent with the trend if not the small details. Some people may have never felt cold like this, and night time temperatures on the snow fields may be more similar to last experienced in South in 1990s 

 

[Model output discussion - Post SSW - Will it turn cold?]

5 minutes ago, blizzard81 said:

Why are the operational runs 'out of kilter miss firers' at relatively short range all of a sudden?

Too many factors

Firstly MJO would indicate with its phase 14 days ago that high pressure should push to our NorthEast

SSW should push everything Westwards - so a contrast here between two major drivers.

A solar wind combined with a CME will hit the Earth tomorrow effecting the Poles, 

So already some major factors which will all effect output

In addition we have the winds at higher altitude reversing and this is moving lower in the atmosphere, timing can vary, as can the strength. In addition where is everything in the troposphere when winds reverse. 

All that on top of everything else that the computers normally have to deal with.

The data higher up will be less than at the surface for higher resolution, so these big changes higher up will be less well recorded and due to the SSW being a less common event, the data inputted will be less good. I mean by that, that the data to move forwards is less well known by human computer data to compute it, plus we have less data from previous SSW events for the computers to learn how to deal with it. The best thing for the computers is a positive NAO as it has more data over more time to understand small implications

[Model output discussion - Post SSW - Will it turn cold?]

14 minutes ago, ptow said:

Just as many going for +5 as -10.  A few towards-15 but not many

What that actually shows is that day 5 we have wide scatter,  day 7 and its about as wide as you can get From plus 9 too minus 13

What its telling us is that the uncertainty starts in quite a big way, at day 5.

Why?

Well we do not see a reversal at 30mb until 18th - which is 4 days away

Huge difference in where it goes depending on very small difference in atmosphere when it actually does reverse,  Few hours earlier or later, slight difference on positions of the high and low's. Orientation of the high. Even then we are waiting for the reversal lower down. 

Until then all the models will play with different ideas. The data is run from the point its taken and under normal conditions its fairly predictable, With this its a different ball game.

There is no default as such, but the models are trying as always to predict what will happen, but with an added ingredient in the mix that increases the shannon Entrope.

We will have this until 17th at least and maybe after 22nd until the models finally get a idea of what is most likely.  we just have to be patient and try not to get excited or disappointed on each run. Trends will become the most useful guide as we head into that period, Current trend is High pressure moving North . You should also notice on that chart a very important feature and that is that the mean  is lower than the long term mean. That hints that it will be colder than average.   

[Model output discussion - into 2018]

1 hour ago, Catacol said:

So - here we go: starting tomorrow the height rises to the NE begin to fade away SE under the influence of falling AAM via low torques, unhelpful MJO phase and background Nina forcing. Ventrice posted this today - atmosphere clearly coupled to the oceanic nina signal.

The logical progression of this is that there is insufficient forcing over the next 7 days to change very much, and let's remember that ECM has an over amplification bias in the extended range - I'm not buying a major block arriving in 7 - 10 days. A coldish pattern with plenty of polar maritime influence... but for lowland south of England we'd need to roll a double 6 to get something significant and even then it would probably be relatively transient. For high ground and the north - plenty more snow potential through this period: always worth acknowledging that not everyone on NW is a lowland southerner!!

But all is most definitely not lost. Taking apart the specific signals - as GP said a post or two ago - there is much for cold lovers to get excited about in the longer term.

Frictional torques have reached their approx cycle minimum

and shortly they will start to climb again. Relative AAM has gone through the floor, down to -3SD at the moment and probably bottoming out at that point

With increases likely from this point as the atmospheric elastic band that constantly tries to keep momentum neutral at 0 kicks in. MJO currently in 2 but ready in around a week or so to move into 3 which has a much better composite for continental flow

What does this all add up to? Chasing shadows for another week via NWP... but from around about this time next weekend we might start to see some very good looking charts hitting NWP output for Jan 20 onwards... maybe a few days later. Frictional torques will lead +MT and combine with MJO phase 3.. well supported by the atmospheric instinct to wipe away that very low relative tendency in AAM. This will encourage steeper incline of the Nina jet into Europe (that Nina forcing will remain so I dont see a Greeny high and -NAO from this) and the scandy high properly fighting back west. Undercut scenarios a-plenty.... and with Strat interest aptly timed to kick in later in the month we may see something of decent duration. It is too far out for me to speak about duration with any confidence... but I think lag effects of MT and the strength of the spring may well help establish a durable and strong scandy high which is then hard to shift... so a week of something cold seems a decent bet and if it went longer then it wouldnt be a surprise.

Eyes will be firmly looking for cold pooling over Eastern Europe in the meantime. Seeing -12 uppers heading for Greece in the modelling for next weekend could well end up being a rather good thing in the longer term...

Catacol 

I see MJO as now moving into phase 3 not in a weeks time but imminent. 

I also see Phase 3 as being the Catalyst for Increasing the NAO towards positive but around 14 days later so for me something rather more mobile around 23rd january

Here is what ECM say about it too

Time lag (days)

• The probability of a positive phase of the NAO is significantly increased about ten days after the MJO is in phase 3 (phase 3+10 days), and significantly reduced about ten days after the MJO is in phase
6 (phase 6+10 days).

• The probability of a negative phase of the NAO is reduced about ten days after the MJO is in phase 3 (phase 3+10 days), and increased about ten days after the MJO is in phase 6 (phase 6+10 days).

I disagree with the 10 day as my data shows few days longer but the rest seems fairly accurate. Obviously we have other drivers that can alter this but around 22nd i would expect very little blocking over Europe. Prior to this i would expect a period where systems move from our North West to South East as we move from the blocked pattern to a mobile pattern. At same time the AO may move into a negative.

The MJO Looks likely to move towards phase 5 by 21st - 24th January  which brings opportunities for European blocking around 1st / 2nd week of February

 

Hope you do not mind me saying this and having a open discussion on thoughts on MJO, as i feel best progression is when members discuss these things and learn from each others data and experience - so its possible i am wrong but this is where we learn

 

[Stratosphere and Polar Vortex Watch]

I use research documents from ECM

 

I also keep records of MJO and effects over Europe

Its good, but occasionally things do the opposite to expected, i believe other factors like SSW and PV sometimes makes it go opposite to as expected, Even when we expect a high pressure to sit at X for example its strength, orientation and exact location can make the NAO less blocked or more so. 6 days ago we were in phase 8 and so blocking likely by 7th Jan or thereabouts but with the MJO moving thru phase 1 and 2 expect it to last around 5 to 7 days where NAO fires up. Research says 10 days for effects over Europe, but my data suggests that must be for first sign of effects as it seems to be more like 12 - 14 days when actual effect takes place.

 

So Nao may start to change day 10 but change more full or complete by day 12/14

But just my take on it and goes somewhat against research from ECM

[Stratosphere and Polar Vortex Watch]

7 hours ago, Singularity said:

Just this one point I wonder about; I have read that phase 3 has some association with a negative NAO, albeit fairly weak in January. At the least this runs counter to the NAO turning more positive as you imply...?

If you can clarify that would be great, thanks .

No positive NAO, with Phase 3

Time lag (days)

• The probability of a positive phase of the NAO is significantly increased about ten days after the MJO is in phase 3 (phase 3+10 days), and significantly reduced about ten days after the MJO is in phase
6 (phase 6+10 days).

We do of course have other drivers which can enhance or mitigate the MJO effect

[Stratosphere and Polar Vortex Watch]

This is rather interesting thou with 10hpa temperature rising quickly over the last few days

We were in COD 12 days before this really started 

[Stratosphere and Polar Vortex Watch]

The MJO has traversed the all important phase 6 and is now in a moderate phase 2, However on getting to this we had a period in COD

This should equate to Scandi high staying in place for a little longer and maybe strengthen a little. The issue is we are quickly heading into a fairly strong phase 3. The NAO should there fore fire up and by 17th of January the Scandi high pushed further North and East

At that point we will see a more Atlantic driven scenario and less cold. To get there we see a transient period with us often on the north side of the Jet, This effected by the High.

Around 14th january the effects of MJO phase 1 and 2 start to allow the Azores high to nudge Northwards with the jet running along the top. This also coincides with Siberian High moving North and East

Those looking for something wintry will see opportunities between now and 13th and then start  to see the Less Cold Atlantic Attack.

We are also then heading rather quickly towards Phase 6 again and i suspect around 20th we will be back in that region (Western pacific)

This leads nicely in to February around the 4th for another opportunity for wintriness 

The biggest challenge is do we have a moderate phase 4 and 5 to get there or will it be via the COD and will the phase 6/7 be strong enough.

The MJO was in phase 5, 10 days before the snow that many had around 10th December so the less cold period may be rather short lived.

The NAO appears to agree with that analysis too but as always time will tell

[Model output discussion - heading into 2018]

17 minutes ago, SilverWolf said:

Poss of topic and apologies if so, but in my memory (I’m 41, so childhood memories..) the last few weeks and what the models are showing reminds me of the early-mid 80’s. I remember a fair few rain to snow events, and milder bits, before and around christmas then something a little more substantial for cold at various times jan/feb. Does this ring true for anyone else with better memories or actual statistics? Just curious about any similarities between then and now/rest of winter, model related or anecdotal. Thanks, if bettter asked elsewhere let me know! 

It does in deed, i might have a look at some old charts for comparison, I know as Brecon beacons used to get back edge snow and would rarely  go more than a day or so with the last snow drifted in a ravine, before next snow fall, its been similar this year for first time in 25 years. We also see similar pattern with backedge snow. 

There was an interesting theory about a mini ice age in 2030 on sky news today regarding magnetic waves from the sun,  i currently only understand the sun spot cycle. 

Models are throwing up some interesting weather towards NYE and beyond into fi

It used to be said in 70s and 80s when USA had big snow we get it 10 - 14 days later, that not happening yet but i wondering if that was MJO related

[Model output discussion - heading into 2018]

7 minutes ago, Catacol said:

Dec phase 8 would have been much better... phase 7 was transition to high lat block, but amplitude fell away. Dont think much will come of this.

I think your more technical than i am on MJO, but on this occasion  i think your wrong

I think we have enough from phase 7 and the little weak phase 8 to bring something wintry, not widespread snow but more than a little back ed ged stuff and possibly to levels 100m and lower. Moderate phase 7 allowing strong Siberian high pressure to cause a blocking pattern that sends low pressure South East across the UK. I admit its not going to bring the perfect conditions that would be a very strong Siberian high that brings Easterlys to the UK thou,

Perhaps i am reading your post wrong thou, and its the Easterlies that you mean when you say a poor performance for cold as yes it does not look to bring that kind of deep cold

[Model output discussion - heading into 2018]

7 minutes ago, mulzy said:

Got a very noobish question about the MJO - if we move into phase 3 for example, is there any lag before we the analogue pattern for that MJO phase becomes applicable or is any response immediate? 

There is a lag of around 2 weeks, i actually use 10 days for pattern change / effect over Europe, the official line i think is a bit quicker but following the phases i find 10 -14 days more accurate.  Phase 7 there fore , with me has effect 1st week of jan and should bring some wintriness. 

I follow 3 experts on here and their input is invaluable with MJO, but also use my own analysis

So answer is yes a lag, but time line may differ from mine

 

Plus no such thing as noonish question, we are all learning and better to ask than never know the answer

[Wales/Cymru Regional Weather Discussion]

Penarth

[Wales/Cymru Regional Weather Discussion]

Blizzseet down in penalty

[Wales/Cymru Regional Weather Discussion]

More likely it will return in South as Snow about 2pm may be bit earlier but pretty much all over by 7pm tonight - then ice overnight

[Wales/Cymru Regional Weather Discussion]

Sorry jay. i must be ten mins behind you, heavy snow here now too

[Wales/Cymru Regional Weather Discussion]

Seriously St Fagans , Culverhouse cross its all sleet

[Wales/Cymru Regional Weather Discussion]

10 minutes ago, Jayfromcardiff said:

Very heavy snow whiteout.

Jay im In cardiff and all i can see is sleet occasionally in rain

10 minutes ago, Jayfromcardiff said:

Very heavy snow whiteout.

 

11 minutes ago, Jayfromcardiff said:

Very heavy snow whiteout.

 

[Wales/Cymru Regional Weather Discussion]

sleet in cardiff

 i think a spell of snow Pontypridd North looks likely and maybe saying as snow in heads of valleys area, maybe snow returning to lower valleys tomorrow daytime, looks miserably wet for us InCardiff till late tomorrow and maybe not enough then 

 

[Wales/Cymru Regional Weather Discussion]

Okay guys

remember the front crossing into West country now is a warm front

It becomes Occluded around the time it catches  us , I believe even with the warm front there has been some sleet on hills. 

Now also if we are lucky the centre of the low will be below the Bristol channel, winds around the Northern side coming from the east, As it passes through we want to see the centre of the low intensify, so we get a circle in the Oval shape dragging winds around from Nw  ( all around from the East) behind it. 

The low could actually be centred just on shore as winds run into the low so even if we are in the circle around the edges air will be moving anticlockwise and inwards.

I think Places like Cardiff will see early wet snow, followed by sleet and rain before more snow later tomorrow.

However any lying snow helps to modify temperatures. 

Heavier precipitation assists where temperatures are marginal with evaporative cooling

However this is really only enough on its own to turn sleet to Snow or rain to sleet , where each droplet moves a parcel of cooler air towards the lower atmosphere and ground

hey all good luck all, i think mid wales , Valleys  and Welsh borders will get a hammering - lucky sods but i would be surprised if by end of tomorrow North cardiff does not have 2CM or more