Model Output Discussion 1st January 2014-06z onwards.

[nick sussex]

Correct as we head into 10-15d trend period (i.e. as affecting S/SE especially). As of 00z EC, circa 40% of EPS members build pressure to NE with increasing easterly component to low-level flow. This signal is one to watch, clearly - especially given some recent similar MOGREPS-15 indications of much colder options (still in a minority but instructive nonetheless). The longer-term colder indication (as per 30d forecast summary) is a separate matter.

That would tie in with looking at the De Bilt ensembles theres a definite two cluster situation appearing and the 11th is decision day! also the temps the trend is generally colder but theres two clusters sub zero for Holland and then cool/cold.

 

This is also very evident with the wind ones, a distinct easterly/se cluster and then  a cluster more towards the south and further round.

 

I think this divergence could be in relation to the amplitude upstream and how far south that troughing digs in the Atlantic, this effects the shortwave track and placement, I think the colder cluster have more dig south in the mid Atlantic which carves more sharpness ahead of it and brings the shortwave further west and then because of that the ridge is further west?

 

Are you allowed to spill the beans on this? could we use a coded system where you just say like and that means you agree with the last paragraph!

[shedhead]

yes all 3 main models suggest what forecasters call a confluent upper trough in about the same place on all 3. From these, surface features can run just ahead of it giving a fair amount of rain, so Met will certainly be watching this probability and their Fax charts show this type of pattern at the surface.

Indeed John, might well be out of the frying pan and into the fire this week, especially for this neck of the woods...hopefully Ian might also be able to shed (no pun intended!) some light on the risks as the MO currently see them.

Edited January 5, 2014 by shedhead

[phil nw.]

Looking at the ECM  mean and allowing for a more diffused picture as it takes into account the colder and milder options it does indicate a continental block forming and colder uppers starting to approach the east of the UK.

Comparing day5 and then 10

 

and the suggestion of the block forcing the Atlantic trough to disrupt se into C.Europe.

 

The fly in the ointment is the GFS ens which still wants to keep the jet over the top and maintaining flat high pressure further south.

day 10

 

so we can see where the split in the ens comes from with the period around days 6-8 where the Atlantic jet shows signs of buckling in the eastern Atlantic-where will main thrust be be beyond this- north or south?

Certainly signs of a slow down in the westerlies continues but the question still to be answered is will we get a Euro high far enough north to get the cold from further east.

Edited January 5, 2014 by phil nw.

[nick sussex]

Just to elaborate more on why we're seeing this divergence at day 7:

 

If you look at the ECM operational run in terms of overall evolution its likely that this is the same general theme of the ensembles as the mean is very closely aligned, the difference is how the ensembles handle the shortwave circled red near the UK and that troughing in the mid Atlantic.

 

 

The red features are basically what we're interested in and its the interplay of these together that will determine whether you get the fast track to cold.

 

Essentially here what happens is as that troughing in the mid Atlantic digs south it carves an angle of the jet ahead of it, so the more dig due south the steeper the bounce north to the west of the UK, this effects the shortwave near the UK, as the jet digs south the shortwave has to go somewhere, it cant move ne because of the ridge to the north so will go either east or se.

 

We would need to see a westwards correction in the output and the jet digging further south to the west and this is probably what the colder ensembles are suggesting.

 

Indeed you can clearly see here the wind directions moving markedly to suggest that:

 

 

You can see from the temps one the distinct cluster between very cold and cool/cold around the 11th/12th January onwards.

 

http://www.weerplaza.nl/15daagseverwachting/?r=midden&type=eps_pluim

 

As everyone knows I can be a bit theatrical but I have to stress we simply must take this opportunity either the fast route or the slightly longer one and have a block sufficiently north before theres a possibility of the jet increasing once again later on. BA made a good post earlier on this issue, if the block is situated favourably then if that fires up we could still see the energy split to the west of the UK rather than just move in and flatten everything.

Edited January 5, 2014 by nick sussex

[Mucka]

I was going to post how a Westward correction would only improve our chances and my thoughts are the same as Nicks above on how that can be achieved.

I don't think this mornings UKMO is a poor chart but if a block developed from there we could easily just find ourselves a little too far West to tap into any deep cold. West is best.

Also if we can get a little energy undercutting we should see any high at a higher latitude but it is entirely possible we high pressure over the UK with a slack continental flow, cold but not particularly exciting. I guess most would take that now though. 

I still think the first attempt around 120/144 looks unlikely to succeed but the second attempt around 168/192 may well work out better if the ridge is strong enough. We could see some quite big changes and exciting developments here if some energy undercuts.

(talking to self as well here )Let's get a block first though and worry about placement. orientation, uppers and snow chances later where detail can be picked out.

 

Looking at the big picture the trends is still in the right direction. That doesn't mean GFS 06z is wrong but given it goes against the trend and doesn't have much support ,even among its own ensembles, it makes sense to set it aside for now. We know there will be run to run variance and even the mean from the ensembles is bouncing up and down run to run. 

Talking of the ensembles I'm surprised a little more wasn't made of this mornings ECM London ensembles - it is the coldest set thus far this winter after all, with a nice cluster of colder options and fewer mild.

Still a way to go and hanging in the balance but a decent morning if you're a coldie or even if you just want things to dry up somewhat though still more rain to get through next week.

Edited January 5, 2014 by Mucka

[nick sussex]

I just love this new toy I've discovered! here the snow predictions for De Bilt, these graph types are much easier to read than the normal ensembles, we can also plot easily the trend to colder weather, I'll be saving these to see how we go day to day.

 

00hrs ECM

 

 

Temps last nights 12hrs

 

 

Todays 00hrs

 

 

You can see there the shift in this mornings output to an increase in colder options.

 

Heres the link again for the main page with all the ensemble data:

 

http://www.knmi.nl/exp/pluim/

Edited January 5, 2014 by nick sussex

[Bobby]

Looking at the ECM  mean and allowing for a more cloudy pattern as it takes into account the colder and milder options it does indicate a continental block forming and colder uppers starting to approach the east of the UK.

Comparing day5 and then 10

120.GIF240.GIF

 

and the suggestion of the block forcing the Atlantic trough to disrupt se into C.Europe.

EDM1-240.GIF

 

The fly in the ointment is the GFS ens which still wants to keep the jet over the top and maintaining flat high pressure further south.

day 10

gens-21-1-240.png

 

so we can see where the split in the ens comes from with the period around days 6-8 where the Atlantic jet shows signs of buckling in the eastern Atlantic-where will main thrust be be beyond this- north or south?

Certainly signs of a slow down in the westerlies continues but the question still to be answered is to we get a Euro high far enough north to get the cold from further east.

 

Here is the NAEFS also for comparison

 

 

Though it has been consistently showing a strengthening in the zonal flow towards the end of the run

 

 

Somewhat similar to the GEFS at the same time and the GEM ensembles

 

 

[sebastiaan1973]

I just love this new toy I've discovered! here the snow predictions for De Bilt, these graph types are much easier to read than the normal ensembles, we can also plot easily the trend to colder weather, I'll be saving these to see how we go day to day.

 

 

Hi Nick, these charts exist for some time now and indeed quite usefull to watch developments.

 

Sometimes I use the charts of winterplaza ('a little sister' of weerplaza)

http://www.winterplaza.nl/

 

This chart below, shows the probability for a vorstdag and ijsdag. Vorstdag means a day with a minimumtemperature below zero. An ijsdag = iceday, maximumtemperature below zero.

 

Ijsgroei= growth of ice

Temperatuur = temperature

Kans op sneeuwval= chance of snowfall

Hellmann wintergetal = the sum of the negative day mean temperature

[stewfox]

Indeed Shed and had this forum been around then there would have been much despondency, strong PV, big euro high I won’t use the B word, just goes to show what can happen. However things right across the NH were different then, arctic ice extent for one thing, back then sea ice coverage in August was as great as it is now at its greatest winter extent, so the winter ice pack back then must have been vast, I’m sure someone can find some data on that. My own theory and I stress that. Is that there is a correlation between winter sea ice cover and the prevalence of HLB across Greenland and Scandinavia and I seriously doubt if we could get another 47 or 63 unless that changes, leastwise our odds against it are substantially greater now. That of course doesn’t mean we can’t get HLB at all as recent years have shown, just that it’s less likely, certainly less likely to be of that extreme nature.

 

 

Sea ice average extent in in the 60s and probably 40s was around 8m in August cf 14m now greatest winter extent.What are you suggesting the Hudson was still frozen in August in the 1940s ?

 

http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm

 

We had the 2nd coldest December (CET) in over 350yrs in 2010 (less summer ice that year) 

 

So basically get the right synoptics and a 47 or 63 will follow as will 2000 cold records being broken in the USA next week.

Edited January 5, 2014 by stewfox

[Vorticity0123]

I just love this new toy I've discovered! here the snow predictions for De Bilt, these graph types are much easier to read than the normal ensembles, we can also plot easily the trend to colder weather,

To add up on the nice list Sebastiaan1973 provided, there is also another feature to analyze wind directions, also found on the KNMI website. On those plots, the wind direction forecast of all 50 members can be seen (oper in red, control in blue).

 

KNMI "windroos" ens (ECMWF 0Z)

 

Every circle indicates 10 knots of wind strength. The circle is divided in 8 subparts, each containing a different wind direction. As with a usual "windroos", the upper part of the circle means northern winds (0 or 360 degrees), the extreme right means eastern winds (90 degrees) etc.

 

Advantages are that the distribution of the wind forecasts up to 10 days can be seen much easier than in the usual "pluim". For example, the wind forecast at day 10 shows 50% giving southwestern winds, and about 40% winds with an eastern component (varying between NE and SE).

 

Source;

http://www.knmi.nl/exp/pluim/windroos.php

Edited January 5, 2014 by Vorticity0123

[Summer Sun]

Darren Bett who was doing the week ahead forecast on BBC 1 said turning colder next weekend at the end of the forecast just before 13:15 how cold who knows but confidence must be growing at Exeter now for a change next weekend

[jvenge]

That's quite a safe thing to say as it looks like midweek is turning very mild again.

 

It will be nice for these storms to stop. The woods around here are like a swamp. Ever saw some flies in the house the other day!

 

It will be interesting to see the next move from the GFS. It seems to have a bias of placing lows two far east from what I've seen over the last month, but other than that, I'm not experienced enough to judge its performance.

[forecaster]

Darren Bett who was doing the week ahead forecast on BBC 1 said turning colder next weekend at the end of the forecast just before 13:15 how cold who knows but confidence must be growing at Exeter now for a change next weekend

 

I remember Derek on BBC Wales hinting at the possibility of colder conditions to come in a piece at the end of November. He was referring to the Dec ~6th cold snap, which barely materialised for most of us. The models really led us astray on that event.

[weather eater]

Sea ice average extent in in the 60s and probably 40s was around 8m in August cf 14m now greatest winter extent.What are you suggesting the Hudson was still frozen in August in the 1940s ?

 

http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm

 

We had the 2nd coldest December (CET) in over 350yrs in 2010 (less summer ice that year) 

 

So basically get the right synoptics and a 47 or 63 will follow as will 2000 cold records being broken in the USA next week.

I was talking about overall ice extent not specific areas, and I did say I could be wrong but I'd be willing to put a fair bit on the fact that we won’t see that kind of 47 63 spell in the rest of my life time, unless we see changes in the arctic, mainly because I think changes in sea ice cover are altering synoptic patterns over this side of the Atlantic, I could go on but it’s not the place, you obviously think differently fair enough.  I did find these, I trust that they are correct, and of as now.

Edited January 5, 2014 by weather eater

[jvenge]

I was talking about overall ice extent not specific areas, and I did say I could be wrong but I'd be willing to put a fair bit on the fact that we won’t see that kind of 47 63 spell in the rest of my life time, unless we see changes in the arctic, mainly because I think changes in sea ice cover are altering synoptic patterns over this side of the Atlantic, I could go on but it’s not the place, you obviously think differently fair enough.  I did find these, I trust that they are correct, and of as now.

Thats probably related to the AMO, which impacts Arctic ice as well.

Check wikipedia for it. You can probably match colder UK winters to it. Assuming you have 5-10 years left, you should see it

[legritter]

Darren Bett who was doing the week ahead forecast on BBC 1 said turning colder next weekend at the end of the forecast just before 13:15 how cold who knows but confidence must be growing at Exeter now for a change next weekend

Friends in Poland just eee mailed me ,they are expecting frigid temp to set in round about the 13th .

[weather eater]

Thats probably related to the AMO, which impacts Arctic ice as well.Check wikipedia for it. You can probably match colder UK winters to it. Assuming you have 5-10 years left, you should see it

Ha not if we don't get off this subject I will get shot by the mods 5-10 years more like 5-10 mins.

[lassie23]

From the models it does look as though any real freeze has been pushed back to February when things finally warm up over the states and a block to our east develops bringing in a month of deep winter for coldies to enjoy. Until then, more of the same, although we may find more frequent NW outbreaks bringing wintry showers later this month. So don't put away the deicer, thermals, etc just yet.

[jvenge]

From the models it does look as though any real freeze has been pushed back to February when things finally warm up over the states and a block to our east develops bringing in a month of deep winter for coldies to enjoy. Until then, more of the same, although we may find more frequent NW outbreaks bringing wintry showers later this month. So don't put away the deicer, thermals, etc just yet.

 

Just curious, but which models? 

[Polar Maritime]

Just curious, but which models? 

 

GFS, ECM..

[lassie23]

Just curious, but which models? 

Plus the latest Korean model for next month.

[Barry12]

From the models it does look as though any real freeze has been pushed back to February when things finally warm up over the states and a block to our east develops bringing in a month of deep winter for coldies to enjoy. Until then, more of the same, although we may find more frequent NW outbreaks bringing wintry showers later this month. So don't put away the deicer, thermals, etc just yet.

 

Most models only go as far out as 10 days ahead, with the GFS going out to 14 days, which at most takes us up to the 19th January, so how can you know what February will be like? Unless your basing it on the CFS which has been useless this winter.

Edited January 5, 2014 by Barry95

[IDO]

GFS 12z much more progressive with cutting off the flow to the ridging to the north of the UK. At least 36 hours earlier than the 0z, and that restores the westerly surface flow . T138:

 

 Very flat.

 

See if a second shot appears after T200.

Edited January 5, 2014 by i'm dreaming of...

[Cumulonimbus Tower]

GFS 12z much more progressive with cutting off the flow to the ridging to the north of the UK. At least 36 hours earlier than the 0z, and that restores the surface flow over the top. T138:

 

gfs-0-138 (1).png  Very flat.

 

See if a second shot appears after T200.

Interestingly has -5 850hPa air flirting with the north west of the UK by next fri/sat though.....

Edited January 5, 2014 by Cumulonimbus Tower

[Methuselah]

Most models only go as far out as 10 days ahead, with the GFS going out to 14 days, which at most takes us up to the 19th January, so how can you know what February will be like? Unless your basing it on the CFS which has been useless this winter.

Ought to change its name to CFG - Chocolate Fire Guard!